Iapetus Sea..............................................................................................................................................................................................................Mer de Iapetus

Mar de Japeto / Mar de Iapetus / Iapetus (Ozean) / 土卫八海 / Море Япета / Oceano Giapeto /

Ocean that existed between Europe and North America, between 570 and 420 million years ago. About 600 million years ago, Europe and North America, which were more or less together, began to separate as the magma of the lower crust rose to the surface to fill the space created by the separation of the continents. About 460 Ma (millions of years ago), North America and Europe collided forming the Appalachians at the same time as the Sea of Iapetus closed. In Greek mythology, Iapetus is the name of a titan son of Uranus and Gaia (Goddess of the Earth).

See : « Supercontinent »
&
« Rodhinia »
&
« Tethys Sea »

The Iapetus  Sea is considered by many geoscientists as a forerunner of the Atlantic Ocean. That is why his name was taken from the Titan Iapetus, who in Greek mythology was the son of Uranus (the starry Sky) and Gaia (the Earth) and father of Atlas, who was condemned by Zeus to sustain the world forever, and from which derives the name Atlantic Ocean, i.e., the ocean beyond the columns of Hercules (Strait of Gibraltar). The Iapetus Sea existed between 600 and 400 million years ago, between the Neoproterozoic and Paleozoic, was formed due to the separation of the supercontinent Protolaurasia (*). Located in the southern hemisphere, this sea was bounded to the west by the Laurentia continent (Scotland, North America and Greenland), to the East by the Baltica continent (Scandinavia and Eastern Europe), to the south by the micro-continent Avalonia (United Kingdom, Northwest Europe), plus other small lands situated west of Avalon (now part of New England, Nova Scotia and Acadia). The Iapetus encompasses the Tornquist Sea, located between the micro-continent Avalonia and the Baltica continent, whose remains today form a suture that extends through northern Europe (Tornquist Zone). During most of the Ordovician, the conditions were highstand and the Iapetus Sea (or Iapetus Ocean) , between the Baltica continent and Laurentia continent, was quite wide and flooded a large part of the cratonic areas. In the Middle Ordovician, the centre of the Baltica continent was to the south of the equator. During the Late Ordovician, the Baltica continent moved towards the equator, whereas England and Southern Ireland were, practically, connected to the northern margin of the small supercontinent Gondwana. It was this displacement, which led the Baltica continent to near the Eastern margin of the Laurentia continent, starting a, progressively, closing of the Iapetus Sea. The volcanic arcs located in the Iapetus Sea collided with the coast of the Laurentia continent causing the first Paleozoic tectonic cycle, which ended with the Taconic** orogeny and the deposit of enormous packages of submarine fans (flysch) and clastic wedges. During the Silurian, the mountains of the Taconic orogeny were, gradually, eroded and the micro-continent Avalonia (fragments of this micro-continent are found in the south-western area of Great Britain and the East coast of North America), derived from the small supercontinent Gondwana went northward and collided with the continent Laurentia. It was in the Silurian/Devonian that the Iapetus Sea closed, completely, and that the Baltic continent merged with the Laurentia continent, at the same time, that England united with Scotland and the southern part of Northern Ireland, which produced the Acadian/Caledonian orogeny. In fact, the Caledonian orogeny was caused by the collision between the Baltica continent and Greenland, which at that time was still connected with Canada. At present-time, most of the deformations caused by the Caledonian orogeny are perfectly visible in almost all of Western Europe, from Scotland to Portugal. The Cambrian and Ordovician fossils are different on both sides of the suture zone marking the closure of the Iapetus Sea, corroborating the presence of this ocean before the Caledonian orogeny. Attention to the term collision used here, since it does not correspond to a kinetic energy change (energy related to the state of motion of a body) in deformation energy such as when two automobiles bump against each other or when a car bumps against a wall (the impact energy is almost totally absorbed by the plasticity of the hull of the car). In plate tectonics kinetic energy does not play an important role. The rocks deform when they lose resistance to deformation, which happens inside a lithospheric plate if, for various reasons, the temperature and pressure increase locally, beyond the limit of resistance to deformation.

(*) Former supercontinent, which was part of the previous supercontinents, Rodhinia and Pannotia. When the supercontinent Pannotia broke, the southeastern part formed the Protolaurasia, located near the South Pole and covered by glaciers (like Amazonia and West Africa). At the end of the Proterozoic, there was a rotation to the West. The Proto-Laurasia began to move away from Proto-Gondwana and to move on through the Panthalassa. During the Paleozoic, the Proto-Laurasia departed which originated the continents Laurentia, Baltica and Siberia, forming two other oceans between the three continents: (i) Iapetus Sea, between the Laurentia and Baltica and (ii) Khanty Ocean, between the Baltic and Siberia. These oceans increased in size, due to the oceanic expansion (sea floor spreading) that occurred during the Cambrian, but a few million years later, the three continents rejoined to form the Laurasia, due to the aggregation of the supercontinent Pangea, which caused the closing of the Iapetus Sea and the Khanty Ocean.

(**) A term coming from the Taconic Mountains that form part of the Appalachians east of the Hudson River.

Ice Age* (Origin)...............................................................................................................................................................................................Époque glaciaire

Época glaciária / Época glaciar (origen) / Eiszeitalter / 冰河時期 / Ледниковый период / Ere glaciale /

Sun radiation is the main parameter that controls the Earth's climate. Any change in radiation has a great influence on temperature and, therefore, on glacial epochs. According to G. Gamov (1950), other hypotheses can be advanced to explain the glacial epochs: (i) Solar Storms ; (ii) Amount of Atmospheric Gases ; (iii) Volcanic Activity ; (iv) Amount of Continental Crust ; (vi) Revolutions of the Galaxies ; (vii) Milankovitch's Cycles, etc.

See: « Glacier »
&
« Milankovitch's Cycle »
&
« Glaciation »

This figure shows the extent of glaciation that occurred during the Early Paleozoic and the mapping of glacial slickensides. These suggest: (a) A drift of the continents and (b) The probable position of the south pole (in relation to the continents). In order to explain the glacial ages, it was necessary to find a mechanism capable of reducing the solar energy received by the Earth's surface, although there is no logical reason to think that the Sun always radiated a constant energy during geological time (the most modern astronomical hypotheses assume that all the stars, like the Sun, increased the luminosity with the time). The brightness of the Sun appears to have increased by 30 to 60% over the last 5 Ga. The study of the Sun's surface shows the existence of cyclical disturbances that appear on average every 12 years and that, in the short term, have an important influence on the Earth's climate. The glacial ages of the Proterozoic may have been induced by the consumption of methane and ammonia from the atmosphere and by the end of a greenhouse effect that seems to have dominated the Early Proterozoic. The formation of the supercontinents can explain the glacial epochs of Precambrian and Late Paleozoic. The other epochs may be partially explained by the shortening and rising of the continents, but the factors most frequently advanced by geoscientists are: (i) Solar storms (solar cycles) ; (ii) Amount of gases in the atmosphere ; (iii) Volcanic activity ; (iv) Quantity of continental crust ; (v) Supernova explosions ; (vi) Revolutions of galaxies and (vii) Cycles of Milankovitch. Note, it takes about 50-100 ky to create a glacial age, but only about 10 ky to destroy it. Fusion of ice does not require an increase in the temperature of all oceanic mass, but only the surface. A deglaciation is faster than a glaciation. The earliest glacial epoch seems to be the Huronian. It, probably, lasted from 2.4 Ga to 2.1 Ga. In the Late Proterozoic, the glaciations of the Cryogenian have frozen the entire planet. However, there seem to have been two main glacial periods, each lasting about 20 My: (i) Sturtian around 700 Ma and (ii) Marinoan there are about 650 Ma. During the Phanerozoic there were three major glaciations: a) Andine/Saharan Glaciation ; b) Karoo Glaciation, which persisted for most of the time of the supercontinent Gondwana and c) Cenozoic Glaciation. The latter may be summarized as follows: (1) In the Early Oligocene, glaciers began to form in the Antarctica, but global temperatures remained, relatively, stable until the Early Miocene and Antarctic glaciation declined during this period ; (2) About 15 Ma ago, the subduction between Central and South America connected the connection between North and South America, preventing the flow of water between the Pacific and Atlantic Oceans, which certainly restricted the transfer of heat from the tropics to the poles, can explain the rejuvenation of Antarctic glaciation ; (3) The expansion of Antarctic glaciation has increased the Earth's albedo, which has promoted an additional cooling cycle ; (4) In the Pliocene (5 Ma) ice sheets began to grow in North America and northern Europe ; (5) The most intense part of the Oligocene/Holocenic glaciation (present glaciation), which is likely to continue in the future, was during the last millions of years ; (6) The Pleistocene was characterized by significant temperature variations (about 10° C) in periods ranging from 40 to 100 thousand years, corresponding to the expansion and contraction of the glacial caps, which have been explained by small changes in Earth's orbital parameters (Milankovitch cycles).

(*) In the geological history were detected at least five glacial ages or ice ages: (i) Huronian ; (ii) Cryogenic; (iii) Andean-Saharan; (iv) Karoo and (v) Quaternary. The Huronian glacial age occurred about 2.4 to 2.1 Ga (10⁹ years ago) during the Early Proterozoic. The Cryogenic ice age occurred between 850 and 630 million years ago and appears to have produced the so-called Terrestrial Snowball, once the ice caps have reached the equator. The Andean-Saharan glacial age occurred between 460 and 420 million years ago, during the Late Ordovician and the Silurian. The Karoo ice age occurred between 360 and 260 Ma, particularly in South Africa (where evidence of this ice age was clearly identified) and in Argentina during the Carboniferous and Permian. The Quaternary glacial age corresponds to a glaciation, which began about 2.5 Ma during the late Pliocene when the glacial caps began to extend in the Northern Hemisphere. At present, Earth is in a interglacial period. The last glacial period ended about 10,000 years ago.

Ice Sea.........................................................................................................................................................................................................................................Mer de glace

Mar de gelo / Banquisa, Hielo marino / Meereis / 海冰 / Морской лёд / Banchisa, Ghiaccio marino, Banchiglia /

Frozen sea-water that floats on the surface of the sea, once the ice is less dense than the water. Ice seas cover about 7% of the Earth's surface and about 12% of the oceans.

See: " Inlandsis"

Iceberg........................................................................................................................................................................................................................................................Iceberg

Icebergue / Iceberg / Eisberg / 冰山 / Айсберг / Iceberg /

Large block of ice, made of fresh-water, that broke from a glacier, built by the accumulation of snow, or an ice shelf (glacier flowing area on the surface of the ocean) and floating in the open sea.

See: « Glacier »
&
« Cryosphere »
&
« Glacio-Eustasy »

We differentiate iceberg from ice sea*. Icebergs are "calved," or form when a piece of a glacier**. Ice seas form from freezing seawater, that freezing slowly forms crystalline water (ice), which does not have room for salt inclusions. In general, the icebergs are classified according to size. The classification of the "International Ice Patrol" distinguishes six large families: (i) Block of Ice, less than 5 m in height and less than 5 m in length; (ii) Large Block of Ice, between 1 and 5 meters in height and with a length between 5 and 15 meters ; (iii) Small Iceberg, between 5 and 15 meters in height and a length between 15 and 60 meters ; (iv) Medium Iceberg, between 15 and 45 meters in height and a length between 60 and 120 meters ; (v) Large Iceberg, between 45 and 75 meters in height and a length between 120 and 200 meters and (vi) Very Large Iceberg, height over 75 m and length longer than 200 meters. There is also a classification based on form. Thus: (A) Tabular iceberg (length-height ratio greater than 5:1 and a flat surface at the top) and (B) Nontabular Iceberg, which may have several forms (dome, pinnacle, wedge, valley, cube, etc.). The density of pure ice is about 920 kg/m³. The density of the sea water is about 1,025 kg/ m³. Thus, as illustrated in this figure, only one tenth of the volume of an iceberg is above water. The shape of the part of the iceberg that remains inside the water is difficult to deduce from the visible part. This is why it is called "the tip of the iceberg" to designate a problem or difficulty, which means that the visible problem is just a small part of a much larger problem. The presence of icebergs is a major problem for offshore petroleum exploration. Drilling vessels may not be anchored to the seabed. They must have a dynamic positioning so they can quickly avoid an iceberg. When I worked on offshore drilling vessels in Labrador, as long as the radar signalised an iceberg 10 km away, the safety light turned yellow and if the iceberg approached 4km, the drilling rig was disconnected and the ship was moving away, to let go the iceberg. In some cases, an iceberg may be diverted by a towing vessel.

(*) Much of the world's sea ice is enclosed within the polar ice packs in the Earth' polar regions: (i) Arctic ice pack and (ii) Antarctic ice pack.

(**) A glacier ​ is made from compacted snow, which is fresh-water.

Ichnofossil.........................................................................................................................................................................................................................Ichnofossile

Icnofossil / Icnofósil / Ichnofossil (Spur fossil) / 追踪 / След жизнедеятельности / Fossil di traccia /

Fossil of trace (passage of an animal) or tunnel or hole excavated by an organism.

See: « Fossil »
&
« Index Fossil »
&
« Glossifungite »

Ichnofossils are vestiges of vital activity (biological activity) of organisms of the past. As an example of ichnofossil we can mention fossils of footprints, tracks of displacement, marks of teeth, excrement, eggs, tunnels, galleries of habitation, etc. Several biological activities may produce ichnofossils: (i) Displacement, footprints, tracks, rails, etc. ; (ii) Food, toothed marks, gastroliths or a stomach stone (rock held inside a gastrointestinal tract), coproliths (fossilised dung), etc. ; (iii) Housing, galleries, dens, tunnels, etc. and (iv) Reproduction, eggs, postures, nests, etc. The fossil features suggest the earliest evidence of animal life on Earth. The earliest traits of arthropods, for instance, are from Cambrian/Ordovician and the tracks in the Ordovician sand allow to determine the behaviour of these organisms. The ichnofossils can give diverse types of information, however, as identical fossils can be created by a series of different organisms, the fossil traces can only inform to us, in a safe way on two thing: (a) The consistency of the sediments at the moment of its deposition and (b) The energy level of the depositional environment. Fossil features are, often, difficult to correlate with a specific horizon. Conventional taxonomy is not applicable, and therefore another type of taxonomy has been proposed. At the highest level of classification, five modes of behaviour are recognized: (1) Domichnia, housing structures that reflect the position of the organism that created it ; (2) Fodinichnia, three-dimensional structures left by animals eating through sediments, such as, for example, lithophages ; (3) Pascichnia, are tracks left by herbivores on the surface of a soft sediment or mineral substrate ; (4) Cubichnia, vestiges of traces, in the form of an impression left by an organism in a soft sediment ; (5) Repichnia, vestiges of traces on the surface of sediments. Many of these fossils are classified into genera, some of which are further subdivided into one species. The classification is based on the implicit form and mode of behaviour. Among the most common genera of ichnofossis are: Asteriacites, Chondrites, Climactichnites, Cruzianas, Entobia, Gastrochaenolites, Petroxestes, Protichnites, etc.

Ideal Equilibrium Profile (River)..................................................................................Profil d'équilibre provisoire

Perfil de equilíbrio ideal / Perfil de equilíbrio provisorio / Vorläufige Gleichgewicht Profil / 理想的平衡剖面（河）/ Временный профиль равновесия (река) / Profilo di equilibrio provisorio /

When the river neither deposits nor digs, in a significant way, its bed. Under these conditions, the slope of the river, along its entire length, allows it only to evacuate its charge. Such a profile is not definitive, since the river continues to transport sediments from upstream erosion.

See: « Regradation »

Illuvial...........................................................................................................................................................................................................................................................Illuvial

Iluvial / Illuvial / Illuvial (Nachdem unterzogen Illuviation) / IIluvial (在经历了淀积作用) / Иллювиальный / Illuvial (che hanno subito illuviation) /

That it has undergone an illuviation, i.e., that it has undergone a deposition of colloids (substance similar to the glue, that does not crystallize and that diffuses slowly), soluble salts and mineral particles leached from a layer of the overlying soil. Synonym with Illuvium.

See: « Soil »
&
« Leaching »
&
« Eluviation »

As illustrated in these sketches, an illuvial or eluvial material is the material displaced through a soil profile (set of horizons that form a soil) from one layer to another by the action of rain-water. In a soil, from top to bottom, we can distinguish seven horizon: O ; P ; A ; E ; B; C ; D and the bed rock (firm rocks). Removal of material from a soil layer is called eluviation. Transport of the material may be mechanical or chemical. The process of depositing an illuvion is the illuviation, which corresponds to a water-assisted transport in the vertical sense (do not confuse with alluviation*. In general, soils are classified according the size of their particles. It can be distinguished: (i) Sandy soils, which have a large part of their particles classified in the sand fraction, of size between 2mm and 0.05mm, formed mainly by quartz crystals and primary minerals, which have good aeration and water infiltration capacity ; (ii) Silty Soils, which has a large part of its particles classified in the silt fraction, between 0.05 and 0.002 mm in size, are generally very erosible ; (iii) Clayey Soils, which have a large part of their particles classified in the clay fraction, of size less than 0.002 mm (maximum size of a colloid) and which are not as aerated but store more water when well structured ; (iv) Latosoils, which have a low cation exchange capacity of less than 17 mol**, the presence of low activity clays and which are generally very deep (more than 2 m) well developed soils located on flat or slightly wavy, with granular texture and yellow to dark red coloration. In addition of types of soils exist, as 1) Leached Soils, which a large amount of rain carries nutrients, making the soil poor (poor potassium, and nitrogen) ; 2) Black Soils, since they are rich in organic matter ; 3) Arid soils, which by the absence of rain, do not develop their soil ; 4) Mountain soils, those in which the soil is young.

(*) Alluviation which is the process that results in deposits of clay, silt, sand, or gravel at places in rivers or estuaries, or along the shores of lakes or seas, where stream velocity is decreased.

(**) The mole (mol) is the amount of a chemical substance that contains exactly 6.02214076×10²³ (Avogadro's constant) constitutive particles, e.g., atoms, molecules, ions or electrons. 

Imbrication (Overlapping, shingling).................................................................................................................................................Imbrication

Imbricação / Imbricación / Schuppenlagerung / 重叠 / Взаимное чешуйчатое наложение (пород) / Sovrapposizione /

Primary deposition of clasts with a preferential orientation such as tiles on a slatted roof or as a series of overturned dominoes.

See: « Sediment »
&
« Transportation (sediments) »
&
" Deposition (clastics) »

In sedimentology, as suggested in this figure, imbrication refers to a primary deposition pattern constituted by a preferential orientation of the clasts so that they overlap one another in a manner, more or less, consistently, somewhat like a series of overturned dominoes. This type of clast orientation allows geoscientists to determine the direction of the original currents. The imbrication of clasts is, mainly, observed in conglomerates and, in certain cases, vulcano-clastic deposits. It can also be observed in certain aeolian deposits. As in conglomerates the shape of many clasts is, approximately, that of an ellipsoid. Three main axes can be seen: (i) The main axis, also called the major axis or A axis ; (ii) Intermediate axis or B axis and (iii) Small axis or C axis. Many geoscientists consider two main types of imbrication: (A) Imbrication along A axis, in which the main (longer) axes of the clasts are oriented parallel to the direction of current flow ; (B) Imbrication according to the plane AB, in which the major axes of the clasts are oriented perpendicular to the direction of flow and (C) Imbrication supported in plane AB, with the intermediate axes of the clasts in the direction of flow of the current. The imbrication along A axis is characteristic of clasts transported in suspension and, therefore, it is just preserved in the case of a fast flow in which the clasts are deposited without any significant bearing. This pattern is typical of conglomerates of the basin floor fan (layer A), but is also, occasionally, observed in alluvial fan reworked by floods. The imbrication according to the AB plane is characteristic of entrainment clasts. This imbrication is formed, for example, when the clasts roll at the base of a channel. As shown in the diagram below, the flattened clasts roll over the downstream clasts and deposit against them with their downstream end resting against the lower clasp, which may be used to diagnose the original flow directions.

Impact (Asteroides, comets).......................................................................................................................................................Impact (Astéroïdes et comètes)

Impacto/ Impacto (asteróides y cometas) / Impakt / 撞擊事件 / Столкновение (астероидов и комет) / Impatto astronomico /

Structure formed on the Earth's surface by the fall of an asteroid or a comet. The impacts of asteroids and comets occurred, relatively, frequently during the Quaternary. One such impact created an important crater in Arizona, about 1,200 meters in diameter and 180 meters in depth.

See: « Geological Principle »
&
« Geological Time »
&
« Continental Collision »

Impacts or better impact craters are geological structures formed when a meteor, a large asteroid or a comet collides with a planet or a satellite. All the internal bodies of the solar system were, heavily, bombarded by meteorites during their history. The surface of the Moon, Mars and Mercury, where most of the geological processes have stopped for many millions of years, the record of such bombardment is very evident. However, on Earth, which was much more bombed than the Moon, impact craters disappeared, more or less, continuously by erosion and deposition, but also by volcanic and tectonic activity. Only about 120 impact craters have so far been recognized on the Earth's surface. Most were found in the geologically stable craters of North America, Europe, and Australia. This figure illustrates the Meteor Crater (or Barringer Crater) in Arizona, which was perhaps the first recognized impact crater on Earth. It was identified in 1920 by workers who discovered fragments of the meteorite (small meteor) inside the crater it caused. It is assumed that this impact occurred about 50,000 years ago when a meteorite of about 50 meters in diameter and with a velocity of about 40,000 km/h collided with the Earth, creating a crater with 200 meters deep and about 1.6 kilometers in diameter. Before the impact, part of the asteroid broke apart, creating a cloud of iron fragments and that, approximately, half of the original 300,000 tons remained intact and hit Earth. On June 30, 1908, an asteroid (small celestial body gravitating around the Sun) of large size exploded above the surface of Siberia (Tunguska event) crushing hundreds of kilometers of forest (near the Podkamennaya Tunguska river), but , curiously, almost left no extraterrestrial traces. Nowadays, using special satellites, scientists have been tracking meteorites the size of cars exploding in the air. Several other craters, relatively smaller, with fragments of the meteorite inside, were for many years the only evidence to corroborate the hypothesis of an impact. Geoscientists have realized that most of the meteor residues do not survive the collision. In the collisions caused by large meteors, enormous pressures and temperatures are created, which can, completely, vaporize the meteor, melt it totally, or form a mixture with the melted rocks. After a few thousand years, any detectable component of a meteor can disappear completely. In some cases, a relatively substantial abundance of non-terrestrial ferroginous elements can be detected in the rocks melted by impact. When, in 1991, A. Hildebrand et al. (1991) suggested that a circular structure, 180 km in diameter, buried in the Yucatan peninsula (Mexico), is an impact crater. The geoscientists who worked on the petroleum exploration in this area finally understood the large circular pattern visible in the gravimetric map of the area, as well as the stratigraphy found by drilling wells inside and around this circular structure : a succession of andesitic igneous rocks a chemical composition and isotopic composition similar to that of tectites (*), inter-stratified and covered by breccias containing evidence of shock metamorphism (pressures above mega-bars and temperatures above 10,000 ° C or more). Presently, many geoscientists think the impact occurred in the Late Cretaceous about 66 million years ago and was probably one of the reasons for the extinction of numerous groups of animals and plants, including dinosaurs. Evidence suggests the meteor could have been a piece of a much larger asteroid that fragmented into a collision in distant space more than 160 million years ago. In March 2010, geoscientists from more than 33 international institutions reviewed the available data and concluded that the impact on Chicxulub is, certainly, one of the causes of massive extinctions in the K-T boundary including that of dinosaurs. However, for other geoscientists, the meteor that struck the planet 66 million years ago was not the only culprit since large volcanic eruptions, in particular, lava flows on the Deccan plateau (India) appear to have been caused by the impact. However, P. Rene of the University of California at Berkeley, who studied such outflows, says, "Based on our lava dating, we can be fairly certain that volcanic activity and impact occurred during the 50,000 years during which extinction. "(http://news.berkeley.edu/2015/ 10/01/asteroid-impact-volcanism-were-one-two-punch-for-dinosaurs/)

(*) Natural glass rocks with dimensions of a few centimeters believed to have been formed as a result of large meteorite impacts on the Earth's surface.

Incised Valley........................................................................................................................................................................................................Vallée incisée

Vale cavado / Valle inciso / Eingeschnittene Tal / 下切谷 / Врезанная долина / Valle incisa /

Valley incised by erosion induced by a significant relative sea level fall, which destroyed the provisional equilibrium profile and which put the sea level below than the basin edge, that is to say, that exhumed the continental shelf and the upper of the continental slope.

See: « Systems Tract »
&
« Relative Sea Level Fall »
&
« Unconformity »

In this photograph, a part of the valley of a stream (area between the top of the slopes on each side of the stream bed) was filled by sediments, probably, during the deposition of the last stage of a lowstand prograding wedge, when sea level was close but still lower than the basin edge. Indeed, the old incised valley, which had been induced by a significant relative sea level* fall, was, totally, filled by sediments, at the same time as the last paracycles of the lowstand prograding wedge (LPW) were deposited starting by rising, in acceleration, of the relative sea level. However, later on, a new fall of the relative sea level, put again, the sea level lower than the basin edge created a new unconformity. As the new relative sea level fall displace the seaward and down the shoreline, as well as the rivers mouths. This new position of the shoreline forced the water-courses to incised further their beds, creating new incised valleys, in order to obtain a new provisional equilibrium. The topographic anomaly (incised valley) induced by a reactivated current is, in this figure, quite evident. The incision was produced by a significant relative sea level fall, in which the tectonic parameter had, probably, an importance similar to eustasy (absolute or eustatic sea level changes). A significant relative sea level fall puts the sea level lower than the basin edge, which destroys the provisional equilibrium profile of the streams (when along the entire water-course the slope allows just the evacuate the load). The streams mouths were displaced downstream (sometimes tens or hundreds of kilometers). Later, during the next marine ingression (relative sea level rise), the incised valley (or incision) will be filled by sedimentary particles forming what many geoscientists, especially, those who interpret the seismic lines, call, in a wrong way, just incised valley. In sequential stratigraphy, the incised valley fillings filling are very useful. They allow the location of the unconformities, especially, when they are not tectonically enhanced, which is the most frequent case. The definitive or ideal equilibrium profile of a water-course is a geological utopia. It implies that along the whole course trajectory, the inclination of the current allows just the flow of the water without any material being transported. The inclination of such a profile, which is given by the fall of formula Chévy-Eytelwein, is so small that, practically, can never be reached. The only profile that interests us is the provisional equilibrium profile that the great majority of geoscientists call just equilibrium profile. It should be remembered that for P. Vail and Posamentier (1988), deltaic deposition occurs when a water-course encounters a water-body, almost immobile, and its velocity decreases, instantaneously, i.e., from the bay-line (boundary between the coastal plain and the alluvial plain). For them, the bay-line corresponds to the continentward limit of the coastal wedge (or coastal prism), which can move upstream when the progradation of the shoreline (outbuilding) is accompanied by aggradation (upbuilding). However, for certain geoscientists, such as Miall, such an encounter of the streams with an almost immobile water-body, which controls their provisional equilibrium profiles, occurs at the mouth of the streams, (head of the deltas), and not at the bay-line. Thus, when discussing the provisional equilibrium profile of a water-courser, geoscientists should always say whether the profile is in relation to the bayline (Vail's position) or to the shoreline (Miall's position).

(*) Local sea level, referenced to any fixed point on the Earth's surface, whether it is the base of the sediments or the floor, which is the result of the combined action of tectonics and the absolute (eustatic) sea level, i.e., of the global sea level, referenced to the Earth's centre. The absolute sea level is the result of the combination of: (i) Tectono-Eustasy, that is controlled by the volume variation of the ocean basins in association with oceanic expansion following the break-up of the supercontinents ; (ii) Glacio-Eustasy, which is controlled by the variation of water volume of the oceans as a function of the amount of ice (assuming that the amount of water in all its forms is constant since the formation of the Earth, there are about 4.5 Ga) ; (iii) Geoidal-Eustasy, which is controlled by the distribution of ocean water caused by variations in the Earth's gravity field (where gravity is stronger than normal, sea level is thrown to the Earth's centre) and (iv) Steric sea level rise or thermal expansion of the oceans (if the temperature increases, the density of the water decreases, and for a constant mass, the volume increases).

Incomplete Sequence-Cycle...............................................................................................................Cycle-séquence incomplet

Ciclo sequência incompleto / Ciclo secuencia incompleto / Unvollständige Sequenz-Zyklus / 不完整的序列周期 / Неполный последовательный цикл / Ciclo sequenza incompleta /

Cycle-sequence in which certain subgroups of sedimentary systems tracts are absent, as, the sequence-cycles composed just by the systems tracts sub-groups of the highstand systems tracts group, i.e., the transgressive interval (TI) and the highstand prograding wedge (HPW).

See: « Stratigraphic Cycle »
&
« Unconformity »
&
« Relative Sea Level Rise »

A sequence-cycle, which is induced by a 3^rd order eustatic cycle (characterized by a time-duration between 0.5 and 3-5 million years), is limited between two consecutive unconformities (or their correlative water-deep paraconformities), whose age difference does not exceed 3 My (or 5 My for certain geoscientists). When in an tentative geological interpretation, the age difference between two consecutive unconformities, i.e, between two significant relative sea level falls, which put the sea level lower than the basin edge, is greater than 3-5 million of years, the stratigraphic cycle is not a sequence-cycle, but, probably, a continental encroachment sub-cycle. Theoretically, a continental encroachment subcycle is formed by several sequence-cycles, which for various reasons can not be, correctly, identified. When the sedimentation rate is very strong, sometimes, within conventional sequence-cycles (those considered in the sequential chronostratigraphy of J. Hardenbol, 1998) several stratigraphic-cycles of upper hierarchy (high frequency cycles) can be recognized. However, usually, they are incomplete cycles. Certain sedimentary systems tracts sub-groups or even groups are absent. On this tentative interpretation of a Canvas auto-trace of a detail of an offshore seismic line from Kalimantan (Indonesia), it is easy to see that between the unconformities SB. 8.2 Ma and SB. 6.2 Ma, as well as. between the unconformities SB 6.2 Ma and SB. 5.5 Ma (conventional unconformities), which define two sequence-cycles, there are other unconformities that limit stratigraphic cycles of 4^th or even 5^th order (SB means "Sequence Boundary"). Some of these high frequency stratigraphic cycles are incomplete. They are, fundamentally, formed by the lowstand systems tracts sub-groups, which within a sequence-cyle, from the bottom up are: (i) Submarine Basin Floor (SBFF) ; (ii) Submarine Slope Fans (SSF) and (iii) Lowstand Prograding Wedge (LPW). The micro-paleontological results of the wells drilled along this seismic profile corroborate the hypothesis accepted by the geoscientist in charge of the interpretation that these high-frequency cycles are sometimes incomplete (often formed just by certain lowstand systems tracts sub-groups). When a geoscientist says lowstand, it does not necessarily speaks in deep sediments. In this particular case, the high frequency sequence-cycles are composed, mainly, of lowstand prograding wedges in which the delta depositional systems are preponderant. In this particular case, the high frequency sequence-cycles are composed, mainly, of lowstand prograding wedges, in which the delta depositional systems are preponderant. Lowstand means that relative sea level fall (sea level referenced to a local point of the Earth's surface which may be the sea floor or the base of the sediment and which is the result of the combination of absolute or eustatic sea level and tectonics) and became lower than the basin edge. Under these conditions, the basin no longer has a shelf (continental platform). It has been exhumed and transformed into a coastal plain. In the photograph shown in the upper left corner of this figure, a sequence-cycle, limited by two unconformities (wavy red lines) can be recognized, whose age difference is less than about 2.5 million years. In this area, from the bottom up, it is easy to identify: (i) The lowstand prograding wedge (LPW), coloured in violet, which fossilizes the lower unconformity ; (ii) The transgressive interval (IT), colored green ; (iii) The maximum flooding surface (dashed line of green colour), which is the upper boundary of the transgressive interval (TI) and (iv) The highstand prograding wedge (HPW), coloured in light brown, which is which is limited, superiorly, by the erosion surface (unconformity) which is the upper limit of the sequence-cycle. The retrogradational geometry of the transgressive interval (IT) is not evident, but it is, relatively, easy to see that this interval thickens continentward (NE). Likewise, the progradational geometry of the highstand prograding wedge (HPW) is not very evident, but the thickening seaward (NW) is obvious. On this tentative interpretation, it is interesting to note the lower unconformity of the considered sequence-cycle limits a forced regression deposited above the high-level prism of the preceding cycle-sequence. A forced regression corresponds to a shifting the shoreline and coastal sediments seaward as a response to a small relative sea level fall, i.e., when the shoreline line is forced to progradate, but downward, regardless of the terrigeneous influx. The seaward shifting of the shoreline triggers erosion processes in both non-marine and shallow marine water environments, which means that the river incision is accompanied by the development of coastal deposits. The deposited sedimentary systems tracts emphasizing a forced regression have a typical downward progradational geometry (descendants sedimentary systems tracts of P. Vail).

Incrustation..................................................................................................................................................................................................................Incrustation

Incrustação / Incrustación / Finkrustung / 结壳 / Инкрустация (накипеобразование) / Incrostazione /

Filling of voids (cracks, fractures, cavities, etc.) or surfaces by a solution substance (calcium carbonate, sodium chloride, silica, etc.) that precipitates by saturation or evaporation of the liquid (Moreira, 1984).

See: « Calcite »
&
« Dissolution »
&
« Stylolite »

As shown in this figure the incrustation is the process of fossilization, which, usually, occurs in sedimentary deposits. relatively, recent tin contact with a limestone source. When a mineral-laden water flows over an organism, the mineral substances can be deposited by incrustation and form a fossil by negative impression. There are other cases of fossilization in fine-grained limestone which have such a rapid consolidation that preserves the more delicate parts of organisms such as the famous fossiliferous deposits of Solnhofen, in Germany, or the famous layers of carbonated shales of Burgess, in Canada. The deposits of Solnhofen (Jurassic) preserved one of the richest fossil faunas in the world. Burguess carbonate shales have conserved organisms from the Middle Cambrian that have made it possible to better understand the evolution of Earth's life. During the burial of fossiliferous rocks, often, the initial elements of the organism remains can be replaced by other elements. It is what the geoscientists call epigenization, i.e., the transformation of a pre-existing mineral into a rock (or a rocky element) into another mineral with the same composition as the chemical composition, by a rearrangement of the crystalline structure, creating a form more stable. Basically, according to the nature of fossilization, three large families of fossils can be distinguished: (i) Fossils by Compression ; (ii) Fossils by Petrification and (iii) Fossils by Incrustation. The former are perhaps the most common and form as a result of organisms or their parts in the sediments, than with burial become flattened due to the geostatic pressure (weight of the sediments). The second are the fossils that hold both the external form and internal structure by a process of mineralization that preserves the vast majority of the cells of the tissues. In fossils by incrustation, the outer form of the organism is preserved as a mold, but the internal structure is destroyed, since deposition occurs in the form of a hard coating around the organism.

Incrusting Water.................................................................................................................................................................................Eau incrustante

Água incrustante / Agua incrustante / Inkrustierende Wasser / 水馅 / Вода, осаждающая накипь / Acqua incrostante /

Water over-saturated with calcium carbonate and therefore prone to precipitate it. Unlike incrusting waters, aggressive waters are those that show a tendency to dissolve CaCO₃. The equilibrium waters, which have no tendency to deposit or dissolve CaCO₃, are conditioned by the values of pH*, Ca²⁺ (hardness) and carbonate (alkalinity) concentration.

See: « Hygroscopic Water »
&
« Juvenile Water »
&
« Hydrologic Cycle »

As water in general is rich in carbon dioxide (CO₂)⁺ and in oxygen (O₂), it can, easily, dissolve minerals such as calcite, gypsum, dolomite, etc., and thus acquire a hardness of several thousand milligrams per lighter and become incrusting. The water hardness underlines the ion concentration of certain dissolved minerals, in particular of calcium (Ca²⁺) and magnesium (Mg²⁺). In fact, the total hardness of a water is, fundamentally, induced by calcite (about 80%) and magnesium (about 20%). When the water is not hard enough, it can become corrosive. Corrosive and incrusting waters can have disastrous consequences. They can corrode or embed pipelines, for instance, and deposit calcium carbonate where it is undesirable. An incrustating water is characterized by: (i) A pH* greater than 7 ; (ii) A total of iron (Fe) exceeding 2 ppm (parts per million, which is equivalent to 1 gram per tonne) ; (iii) A total of manganese (Mn) greater than 1 ppm in conjunction with a high pH and the presence of oxygen and (iv) A total hardness of carbonates greater than 300 ppm. On the other hand, a corrosive water is characterized by: (i) A pH of less than 7 ; (ii) A dissolved oxygen content of more than 2 ppm ; (iii) An amount of hydrogen sulphide (H₂S) greater than 1 ppm ; (iv) A total dissolved solids content greater than 1000 ppm ; (v) A dissolved CO₂** amount greater than 50 ppm and (vi) A quantity of chlorides (natural hydrated magnesium silicates with varying proportions of associated minerals such as quartz, calcite chlorite dolomite, etc.) greater than 500 ppm. Sea water and other salt-laden solutions tend to flow slowly along fractures and cracks without significant water flow. The result of this phenomenon is the deposition of crystalline crusts in certain places and in particular in industrial piping systems. This type of deposition occurs preferably in areas where there is no contact with atmospheric air. As shown in this figure, deposits of carbonate and calcium stearate (the main component of the white precipitate that forms when the soap is mixed with a limestone) occur where hard water evaporates, even partially. This type of deposition can start as a simple residue of rapid evaporation, but its continuation can build thick incrustations.

(*) The pH or hydrogen potential is a measure of the chemical activity of the H⁺ ions of a solution (homogeneous mixture of two or more non-interconvertible substances), especially in aqueous solutions where these ions are in the form of H₃ O⁺ (hydronium or hydroxonium which is the simplest form of the cation oxonium). The pH indicates the acidity or basicity of a solution. When pH <7 the solution is acidic. When pH> 7, the solution is basic or alkaline. The pH can be less than 0 and greater than 14 for very strong acids and bases.

(** ) Carbon dioxide (CO₂) consists of a carbon atom covalently double bonded to oyygen atom. It is a colorless gas with a density higher than that of dry air (around 60% higher).

Index Fossil...................................................................................................................................................................................Fossile caractéristique

Fóssil característico / Fósil característico / Leitfossil / 指準化石 / Руководящие ископаемые / Fossile guida /

Fossil that identifies and dates a layer, in which it is typically found. A characteristic fossil must have a wide spatial distribution, even global and be restricted to a short stratigraphic range and short duration. These fossils help geoscientists to date other fossils found in the same sedimentary layer. When one finds a fossil of an unknown age near a fossil of a known age, it can be assumed that the two species cohabited at the same time. Synonym of Fossil Guide.

See: « Relative Age »
&
« Fossil »
&
« Geological Time »

Trilobites were very common during the Paleozoic Era, between 540 and 245 million years ago. Half of the Paleozoic fossils are trilobites, which became extinct during the Late Permian period (about 248 million years ago). An exception has to be taken into account. The trilobites of the order Proetida disappeared at the end of the Devonian. The trilobite illustrated in this figure is of the species Asaphiscus wheeleri, which is characteristic of Cambrian. Wheeler's shales form the famous fossiliferous outcrops of old Cambrian (about 507 Ma) of Western Utah (USA) where this species is very well represented. Soft body organisms are also found in this outcrop (such as Naraoia, Wiwaxia and Hallucigenia) with a conservation type (carbonate film), which i,s usually, found in the famous Burgess clays (one of the most famous fossiliferous outcrops, which is famous for the exceptional preservation of the Middle Cambrian fossils). Together with the Marium Formation and the Weeks Formation (lower), the Wheeler's shales form an outcropping of clay and limestone rocks of about 600 meters, which is one of the thickest and fossiliferous outcrops of the Middle Cambrian USA. Among other characteristic fossils are: (i) Inoceramus labiatus (Inoceramus from Cretaceous), fossil guide or characteristic for the Early Turonian ; (ii) Tetragraptus fructicosus (Ordovician Trilobite) ; (iii) Leptodus americanus (Permian Cephalopod) ; (iv) Cacotocrinus multibrachiattus (Mississippian Paraflusilin) ; (v) Hexamoceras hertzei (Silurian Ammonite) ; (vi) Viviparus Glacialis (Early Pleistocene Mollusc), etc. In Paleontology*, each fossil species (any definition satisfies all geoscientists, yet they know, vaguely, what they mean when they speak of a species) has a period of its own existence. Normally, it is not possible to determine the exact age of a sedimentary interval, such as that of a sequence-cycle, with a single fossil. It is necessary to study an association of fossils (taphocenosis**). Indeed, a more or less, exact determination of the position of a sedimentary interval on the stratigraphic scale, at the base of its fossils, can be made by studying its taphocenosis, looking for the level compatible with the joint occurrence of all the species present, this with a biozone (a base unit corresponding to a set of strata distinguished by the presence of species or a set of a characteristic fossil). As shown in this figure, trilobites have lived in a period of time that is very different from that of ammonites. Ammonites are molluscs with a partitioned shell that can have different sizes and shapes. Most shells are shaped like a ram's horn similar to the horns that adorn the representation of the god Jupiter Ammonn (Greek / Egyptian divinity combining ammonites with a partitioned shell that may have different sizes and shapes. the characteristics of the Egyptian god Amon and the Greek god Zeus) and hence its name (http://sef.xena.ad/lcf/brian/ammonites/ammonites). The belemenites are cephalopods (such as squid and octopus), which lived in the Jurassic and Cretaceous. Fossils of entire belemenites are extremely rare, since soft parts fossilize very poorly. However, fossils of the hard part, that is, the face ("devil's finger" or "rifle bullet"), which represents about 1/5 of the size of the animal and can reach 30 cm in length, are easily (http://science-nature.e-monsite.com-/pages/quelques-fossiles.html). During its evolution the ammonites, which have tentacles like octopuses and look like squids, have undergone transformations that allow to date marine environments. The ammonites lived in the Mesozoic era. They appeared about 380 million years ago (Devonian) and disappeared with the Cretaceous dinosaurs (more than 68 million years ago). When a geoscientist finds in the field a fossil of a trilobite, he considers that the rock deposited in the Paleozoic. In fact, there are no trilobites after the end of the Paleozoic. If a geoscientist finds a rock with a belemenites faces, he considers that the rock deposited in the Mesozoic and most probably in the Cretaceous or Jurassic. In the same way If he finds a rock with a fossil of ammonites, he immediately excludes that the rock has deposited in the Tertiary, since there was no ammonites after the Mesozoic. Trilobites were very common during the Paleozoic Era, between 540 and 245 million years ago. Half of the Paleozoic fossils are trilobites, which became extinct during the Late Permian period (about 248 million years ago).

(*) Science that studies the life of the Earth's past and its development over geological time, as well as the processes of integration of biological information into the geological record, i.e. the formation of fossils.

(**) Stage of formation of a paleontological site in which the association of organic remains transported from the place where the death took place with organic remains originated in situ and their subsequent burial occurs. In this stage, the skeletal, larval, skeletal, cartilaginous or chitinous skeletons and / or slightly signified plants are eliminated. (http://www.enciclonet.com/articulo/tafocenosis/).  Set of organisms that are fossilized together.

Infauna............................................................................................................................................................................................................................................Endofaune

Endofauna / Endofauna / Tiefseefauna / 海深, 动物 / Бентосная фауна / Fauna profonda /

Aquatic invertebrates that live in holes, tunnels (dug by them) or any other type of shelter within the sediments of the seabed.

See: « Benthos »
&
« Sea floor »
&
« Infauna »

As said above the infauna are benthos that live buried in the bottom of the sea. Bacteria* and microalgae can also live in the interstices of sediments of the sea floor. The animal infauna, progressively, becomes rarer as the water-depth and the distance to the shoreline increase. In contrast, the amount of bacteria remains, more or less, constant (roughly one billion cells per millimetre of interstitial water). Although the term fauna encompasses live animals in a region at a given geological time (flora is the term for plants), other terms: a) Macrofauna is, often, used to denote benthic (organisms living on the bottom of a body of water) and which are at least one millimetre in length ; b) Megafauna is the term, which encompasses all the great animals of a particular region at a given geologic time ; c) Meiofauna encompasses benthic invertebrates, which live in both marine and freshwater environments. The term meio-fauna, more than a taxonomic group, defines, above all, a group of organisms larger than those of the microfauna and smaller than those of the macrofauna. Practically, these organisms pass through a 1 mm mesh, but are retained in a 45 μm** mesh, although the exact dimensions vary with the authors. The mesofauna is formed by macroscopic invertebrates such as arthropods, while the microfauna encompasses all small or microscopic animals such as protozoa. In this scheme of the bottom of the sea one recognizes an endo-fauna formed by: (1) Cirripids ** (Balaniden) ; (2) Blue Mussel (Mytilus edulis) ; (3) Polychaete Lanice conchilega; (4) Polychaete Lagis koreni ; (5) Snail Littorina littorea ; (6) Mollusk Razor (Ensis americanus) ; (7) Bivalve Cerastoderma edule ; (8) Bivalve Scrobicularia plane ; (9) Bivalve Mya arenaria; (10) Polychrome Arenicola marine ; (11) Polychaete Hediste diversicolor and (12) Bivalve Macoma Baltica.

(*) Unicellular microbes of elongated form - bacilli -, spherical - coccus - or spiral, without nuclear membrane and that feed according to the vegetal mode.

(**) The micrometre (μm)  is equalling  1×10^-6 metre  or 0.001 mm (around 0.000039 inch).

(***) Infra-class within the Maxillopoda class of marine crustaceans, with about 1220 species, which includes barnacles and goose barnacles (order Pedunculat), which are filter-feedong crustaceans that live attached to hard surfaces in the ocean intertidal zones.

Infauna (Deep fauna).................................................................................................................................................................................................Faune profonde

Fauna profunda / Fauna profunda / Tiefseefauna / 海深，动物 / Бентосная фауна / Fauna di alto mare /

Set of organisms that live in the sediments of the bottom of the aquifer bodies, like oceans, lakes or rivers. Deep-water animals become rarer and rarer as the water-depth and distance to the shoreline increases. Most of the deep-fauna lives in the first few centimeters below the sea floor, where oxygen is still available. The most familiar and most easily visible animals are clams, worms, crabs, echinoderms, fish, etc. Synonym with Endo-fauna.

See: « Benthos »
&
« Fossil »
&
« Pelagic (organism) »

Deep fauna or infauna (endofauna), as certain geoscientists say, are benthos that live buried in the mud at the bottom of a water-body (worms, lamelibranchs, etc.). On the contrary, the benthos, which live on the surface of the seabed, connected to objects or moving freely form the epifauna that is characteristic of intertidal zones (seaweed, anemones, sponges, crab molluscs, etc.). The infauna encompasses aquatic animals that live within the substrate rather than their surface, that is, at the bottom of the sea. Bacteria and microalgae can also live in the interstices of the sediments of the sea floor. On average, in-fauna animals are, progressively, rarer as water-depth and distance to the shoreline increase, while bacteria have more constancy in abundance, sometimes more than a billion per millilitre of interstitial water. This figure illustrates the study of the animals of the deep fauna, in three different areas. These animals ingest or displace the sediments around them as they move. Many of them, sometimes extremely, numerous, have dimensions smaller than 50 millimetres. These small organisms, designated as microfauna, are studied, usually, under a microscope. The intermediate fauna, between the macro-fauna and microfauna, is called meiofauna. The meio-fauna is also known as interstitial fauna, due to the fact that it occupies the space between the sedimentary particles. Animals that swim, such as fish, mammals and marine reptiles that can move independently of the currents, form the necton. Animals and plants, including the juvenile forms of many molluscs and crustaceans, as well as the single-celled organisms that drift with the currents form the plankton.

Inflationary Expansion (Theory).........................................................................Expansion inflationnaire (Théorie)

.Expansão inflacionária / Expansión inflacionaria (teoria) / Inflation (Kosmologie) / 宇宙暴漲 / Инфляцио́нная моде́ль Вселе́нной / Inflazione (cosmologia) /

Expansion state, extremely fast, which the primeval Universe seems to have suffered. If this theory is correct, our Universe is, practically, flat and the average density is very close to the critical density.

See: « Early Universe »
&
« Critical Density (Universe) »
&
« Big Bang (theory) »

At the beginning of its life, the Universe underwent a particularly rapid expansion*. Astronomers have known for some years that the Universe is expanding according to Hubble's law, which implies that the Universe began at a definite point in the past. Astrophysicists thought that by doing the opposite way of Hubble's expansion, by applying the proper laws of nature everything would be finally understood. Several problems escaped the solutions, each dealing with a fundamental question and not about the beginning of the Universe. The questions were: (i) The Antimatter Problem ; (ii) The Horizon Problem and (iii) The Flatness Problem. The antimatter problem expresses the laws of physics deal with matter and anti-matter on an equal footing, but the Universe is made almost entirely of matter. The horizon problem expresses the fact that judging from the cosmic background radiation that we can detect, the Universe is almost all at the same temperature, but different areas that were not in contact with each other, are not in thermal equilibrium. The flatness problem translate the fact that the Universe seems to have almost exactly the amount of mass and energy required to slow down and stop Hubble's expansion. With inflation, however, the Universe was much more compact before 10^-35 seconds than one might think assuming the reverse unwinding of Hubble's expansion. During this highly compressed period the thermal equilibrium was established, which survived over the period of inflation. Inflation does not solve the anti-matter problem but other events that occurred at the same time. When particles are being forged at the beginning of the Universe, about 10000,000 antiparticles are created for every 10000,001 ordinary particles. Over the next fraction of a second, a pair of particles and anti-particles annihilate each other and in an explosion of energy, which essentially corresponds to a mass conversion of radiation. When this selective process has ended, what has resulted is a bit of ordinary matter. All known Universe was made from these "junk" bits.

(*) Universe began to expand at the speed of light. If the expansion had always been at that speed, the present radius of the visible Universe would be the real ray of the Universe, which does not seem to be true. Therefore, the scientists proposed a scheme called "Inflation Model" according to which between 10^-33 and 10^-32 seconds after the Big Bang, the Universe would have expanded at a speed much greater than the speed of light. Its radius would have grown from 10^-33 seconds light, which equals 3 x 10^-2 meters, up to 0.1 meters. The time interval between 10^-33 and 10^-32 seconds corresponds to 0,9 x 10^-32 s. As the distance covered by the light during this time is 2,7 x 10^-2 meters, the expansion rate was 0,1/27 x 10^-24 = 3,7 x 10²² times faster than at the speed of light. Then the Universe would have continued to expand at the speed of light (C. Emiliani, 1995). If the inflation model is correct, the current radius of the Universe would be 3,7 x 10²² times larger than the radius of the visible Universe. If spherical, the entire Universe would contain about 5 x 0⁶⁷ universes as wide as the visible Universe.

Inflationary Universe.........................................................................................................................................Univers inflationnaire

Universo inflacionário / Universo inflacionario / Inflationäre Universum / 宇宙膨胀 / Инфляционная Вселенная / Universo inflazionario /

Model of the Universe suggesting an important inflation epoch of expansion to solve a number of problems created by the Big Bang theory.

See: « Big Bang (theory) »
&
« Hubble's Constant »
&
« Universe (age) »

Cosmic inflation is a theory first proposed by Alan Guth (1981), which postulates that the Universe, at its initial moment, went through an exponential growth phase*. According to this theory, inflation was produced by a negative vacuum energy density or a kind of repulsive gravitational force. This expansion can be modelled with a non-zero cosmological constant. The whole observable Universe could have originated in a small region. In the standard cosmological model or Big Bang, there are three fundamental problems: (i) The Horizon Problem, an imaginary boundary around a black hole from which the force of gravity is so strong that even the light itself can not escape of a black hole, since its velocity is less than the escape velocity of the black hole, and where the laws of physics can not be applied ; (ii) The Flatness Problem, in the current universe, the density of energy is very close to the critical density (density necessary for the Universe to be planar) ; (iii) The Abundance of Magnetic Monopoles Problem and other topological defects, which suggest that the breakdown of "super-symmetry" i.e., the symmetry that relates a fundamental particle with a certain spin value to other particles with spins** different by half unit, leads to the production of many "unnecessary" relics such as massive and extremely stable magnetic monopoles, cosmic strings and topological defects in space time-conditions analogous to imperfections in the crystal structure of a crystal. The theory of the inflationary universe that proposes a solution to solve these difficulties. However, it is not known what caused the inflation. Some authors think it may have occurred in association with a phase transition. The transformation of water into ice (liquid-solid), for example, is a phase transition that releases latent energy from water. A phase transition in the Big Bang would have released latent energy, responsible for the sudden expansion of the Universe.

(*) Universe began to expand at the speed of light. If the expansion had always been at that speed, the present radius of the visible Universe would be the real ray of the Universe, which does not seem to be true. Therefore, the scientists proposed a scheme called "Inflation Model" according to which between 10^-33 and 10^-32 seconds after the Big Bang, the Universe would have expanded at a speed much greater than the speed of light. Its radius would have grown from 10^-33 seconds light, which equals 3 x 10-25 meters, up to 0.1 meters. The time interval between 10^-33 and 10^-32 seconds corresponds to 0,9 x 10^-32 s. As the distance covered by the light during this time is 2,7 x 10^-24 meters, the expansion rate was0,1/27 x 10^-24 = 3,7 x 10²² times faster than at the speed of light. Then the Universe would have continued to expand at the speed of light (C. Emiliani, 1995). If the inflation model is correct, the current radius of the Universe would be 3,7 x 10^-22 times larger than the radius of the visible Universe . If spherical, the entire Universe would contain about 5 x 10⁶⁷ universes as wide as the visible Universe (C. Emiliani, 1995).

(**) Associated intrinsic quantum property to each particle, characteristic of the nature of the particle in the same title as its mass and electric charge.

Inflection Line (Berm)...................................................................................................................................................Ligne d'inflexion (Berme)

Linha de inflexão / Línea de inflexión (de berma) / Inflexionslinie / 拐点线 / Линия изгиба / Linea di inflessione /

Step that separates the nerashore (space reached by the swash currents, between the neap high-tide and low-tide) of the shoreface.

See : « Shoreface »
&
« Berm »
&
« Average Storm Wave Base »

The nomenclature of the morphological forms that constitute what is, usually, called the coast varies a lot of function of the country and the geoscientists. The coastline (littoral) is a strip of land that constitutes the area between a sea and land (continent or interior). According to the scales, the littoral can extend from a few hundred meters to several kilometers from both sides of the land-water limit or, in strict sense, it corresponds to the space between the strand and the cliff. The coastline is, typically, formed by three zones: (i) Subtidal zone ; (ii) Intertidal zone (strand) and (iii) Supratidal zone. In this glossary we will use one of the nomenclatures most followed by Portuguese geoscientists*. As illustrated in this scheme of a beach, i.e., of a coastal zone with a strand (intertidal strip, which associates a part of the backshore with the entire foreshore) composed of terrigeneous, sandy, sandstone/silty and coarse detrital materials. In general, from the sea to the mainland, different areas can be distinguished: (i) Longshore ; (ii) Foreshore (sensu stricto) ; (iii) Nearshore ; (iv) Backshore and (v) Inshore. The longshore is the part of the beach, which is always submerged and extends outward from the limit of the lowest tides, which certain geoscientists consider as equivalent to the surf wave zone. The foreshore (sensu stricto) corresponds to the lower part of the strand and which comprises the space that extends between the limits reached by the spring low-tide (tides of small amplitude during the Moon quadratures, i.e., during the phases of growing quarter and waning quarter) and the neap high-tide (tides of great amplitude during the phases of full moon and new moon). The nearshore is the part of the beach, which extends in the space reached by the swash currents**, between the spring high tide level and the neap high-tide level. The nearshore it is separated from the backshore by the lower beach step (3 in this morphological sketch) and, from the foreshore (sensu stricto), by another step, which certain geoscientists call inflection line (9), being the escarpment of the beach (10, in this sketch) the beach scarp of the last step. The backshore is the upper part of the beach, with a steep slope that is only reached by the waves in the spring high tides*** and during the storms. When the backshore is very extensive it has small domed dune obstacle, on the other hand, the surface of backshore hit by the waves is modelled on steps, called beach steps, which are formed by a platform (berm of the beach ) and an abrupt (beach scarp). The inshore is the form of relief that constitutes the inner boundary of the beach, which may be a cliff or a barrier bar and that can isolate an interior lagoon. The inflection line (9) of the foreshore sensu lato (between the nearshore and the foreshore sensu stricto) should not be confused with the inflection lines between the berms (5) and the abrupts (beach scarps) of the steps, that is, the berm-ridges, of which the higher is beach-ridge (4, in this sketch). As the onshore corresponds, more or less, to the surf zone, it is natural that the sea floor, in this area, is modelled by longshore ridges and longshorerunnels, which can reach more than 1 meter of height (11 and 12). Obviously, in conventional seismic lines, due to seismic resolution, it is very difficult or practically impossible to recognize a beach and especially its morphological sub-divisions. The horizontal seismic resolution is the ability to distinguish between objects, that is, to see a second object in the presence of another. The vertical seismic resolution is the distance between two interfaces so that there are different reflections or the thickness that should have an interval for top and bottom reflections can be distinguished.

(*) Moreira, M. E. A., (1984)- Glossário de termos usados em geomorfologia litoral. Estudos de Geografia das Regiões Tropicais- 15, Centro de Estudos Geográficos, Lisboa.

(**) Uprush current, which is directed to the coast after the wave breaking and backwash current, which is directed to the sea, following the slope of the sea floor, which results from the inversion of the current, due to the loss of energy caused by the slope and the friction of the sea floor. Do not confuse swash currents with the currents marked by the increase in offshore coastal activity caused by a wind field in open sea (over areas that may have thousands of square kilometers), such as increased waves, both in size as much force, that advance, usually, on the strip of sand, sometimes reaching urbanized areas causing damages and the elevation of the tide. The set of characteristics of kind of currents varies greatly according to the morphology of the coast.

(***) Although only three stars are at stake, their movements are quite irregular. The orbits of the Earth and the Moon are not circular but elliptical, that is, the distances between the stars are not fixed. The plane where the Earth's orbit (called the plane of the ecliptic because that is where the eclipses occur) does not coincide with the plane of the Equator. In addition, the plane of the Moon's orbit forms a fixed angle with the plane of the ecliptic, but it rotates slowly, completing that rotation in 18.6 years which is the highest periodicity associated with the tides - lunar nodal cycle. When the star that causes the tide, be it the Sun or the Moon, is on or near the Equator, the tides tend to have a greater amplitude. In the case of the Sun this phenomenon occurs on the equinoxes: the spring is usually on 21 March and the autumn on 23/24 September. The living tides that occur near the equinoxes are called equinoctial living tides. In fact, the tides of greater amplitude of each year tend to occur near this period, more month less month. (http://www.hidrografico.pt/glossario-cientifico-mares.php).

Inflection Point (Beach scarp)..........................................................................................................Point d’inflexion (Abrupt de la plage)

Ponto de inflexão (abrupto de praia)/ Punto de inflexión (escarpa de playa) / Wendepunkt (Strand Böschung) / 拐点 (海滩崖) / Точка перегиба (Откос пляжа, береговой уступ) / Punto di flesso (brusco dalla spiaggia) /

Beach escarpment between the shoreface and the nearshore. It is the downstream limit of the nearshore.

See: « Beach Scarp »

Inflection Point (Relative sea level curve)................................................................................................................Point d'inflexion

Ponto de inflexão / Punto de inflexión / Wendepunkt / 拐点 / Точка перегиба / Punto di flesso /

Point at which a curve or arc changes from concave to convex or vice versa. The inflection point of a sinusoidal sea level curve is where the rate of fall or rise of sea level is at its maximum value, i.e., where the first derivative of the curve is maximum. The limits of a sequence-cycle are, roughly, at the inflection points of the relative sea level curve, when relative sea level falls. A condensed stratigraphic section is formed before or at the inflection point of the relative sea level curve, when sea level rises.

See: « Relative Sea Level Change »
&
« Eustasy »
&
« Rate of Relative Sea Level Change »

In mathematics, and in particular, in differential calculus*, a point of inflection or simply inflection, is a point on a curve in which the curvature (the second derivative**) changes the signal. The curve changes from upward concave curvature (positive) to an downward concavity (negative curvature), or vice versa. In a metaphorical way it should be said that when a geoscientist, the field, drives his land-rover along a winding road, the inflection point is one in which the steering wheel is, momentarily, straightened when the curve changes from left to right or vice versa. In this figure is illustrated a curve of relative sea level changes, which is the result of the joint action of absolute (eustatic) sea level (supposed global and referenced to the Earth's centre) and tectonics (subsidence, when sediments are lengthened or uplifted when the sediments are shortened). The subsidence is considered linear, i.e., increasing, progressively, seaward. The curve of relative sea level change can be considered, from the mathematical point of view, as a sine-wave, which represents, graphically, the sine function*** and also function itself. Thus, it can be said that the function is increasing and concave at each point, where the 1^st derivative and the 2^nd derivative are positive. When the function is increasing and convex, the 1^st derivative is positive, but the second is negative. This means the function grows, but less rapidly, the derivative of the derivative changes signal****. When the function is decreasing and concave the 1^st derivative is negative, but the second is positive. Finally, when the function is decreasing and convex, the 1^st and 2^nd derivatives are negative. The limits of the eustatic and stratigraphic cycles correspond to the points where the rate relative sea level fall is maximum (points where the 1^st derivative of the curve is maximum or maximum slope). A sequence-cycle (stratigraphic cycle) is, more or less, limited between two consecutive downward inflection points of the curve of the relative sea level changes. These points correspond to two significant relative sea level fall, which put the sea level lower than the basin edge of the underlying sequence-cycle. During a relative sea level fall, not only does an erosional surface (unconformity) is formed, but also, in the deep basin, submarine basin floor fans (SBFF) and the submarine slope fans (SSF) are also deposited. Since the rate of the relative sea level fall goes into deceleration (sector below the inflection point, which is the point that has a maximum derivative of the curve, i.e., the deeper tangent) the lowstand prograding wedge (LPW) begins to be deposited. The deposition of the lowstand prograding wedge (LPW) continues until the relative sea level begins to rise in acceleration (after the lowest point of the curve, which is characterized by a zero derivative, since the tangent to the curve at this point is horizontal). When the relative sea level begins to rise in acceleration, the first flooding surface of the coastal plain of the lowstand prograding wedge occurs), which marks the beginning of the deposition of the highstand systems tracts group (deposit of the transgressive interval, TI). The maximum of the marine ingression corresponds, more or less, to the ascending inflection point, which underlines the limit between the transgressive interval (TI) and the highstand prograding wedge (HPW). That means, the highstand prograding wedge (HPW) is deposited, since the relative sea level rise becomes to decelerated. When the relative sea level fall is not sufficient to put the sea level lower than the basin edge, which is now given by the coastal plain edge of the highstand prograding wedge (HPW), the bordering prograding wedge (BPW) is deposited, until the rate of the relative sea level fall is maximum (upper limit of the sequence-cycle). At present, the vast majority of geoscientists using sequential stratigraphy no longer consider bordering prograding wedge (BPW). They prefer to use the concept of forced regression induced by the seaward displacement of the shoreline in response to a relative sea level fall that occurs during the falling phases of the base level when the shoreline is forced to regress by the fall of the base level independently of the terrigeneous influx, which triggers erosion processes in the sedimentary environments adjacent to the coast line, both in the non-marine and in the shallow marine waters.

(*) The differential calculus considers the relation between parts of a geometrical figure when parts become infinitely small. The integral calculus has an exactly opposite task: the integration of infinitely small parts onto geometrical figures of final size.

(**) Newton call it fluxion and Leibniz call it derivative. The second-order derivative of a function, or second derivative, represents the derivative of the derivative of this function. In symbols, the second order derivative can be represented by y'' or d₂y /d₂x, where y is a function of x. Roughly speaking, we can say that the second order derivative of a function measures the rate of change of the very variation of this function. For example, the second-order derivative of an object's position with respect to time is the instantaneous acceleration of this object, which would be the rate of change of its velocity.

(***) In the function f (x) = sin x, each point in the graph is of the form (x, sin x), since the ordinate is always equal to the sine of the abscissa, which is a real number representing the arc length in unit of measure length of the arc in radians (a measure of an arc whose length is equal to the radius of the circumference that contains said arc).

(****) Do not forget that 1^st derivative is the rate of change of position (e.g. the velocity of a car, in a given point, is the rate of change of position of the car). The 2^nd derivative is the rate of change of the rate of change of position (e.g., the acceleration of a car in a given point is the rate of change of velocity of the car.

Ingression (Marine).................................................................................................................................................................................Ingression (Marine)

Ingressão (marinha) / Ingresión / marine-Ingression / 海洋侵入 / Ингрессия (мосркая) / Ingressione marina /

Migration from the shoreline toward the mainland due to a relative sea level rise. Sometimes synonymous with eustatic paracycle, when the rising of the relative sea level is at the level of a third order eustatic cycle (sequence-cycle) and limited between two flooding or ravinment surfaces.

See: « Relative Sea Level Change »
&
« Transgression (marine Ingression) »
&
« Marine Regression »

A marine ingression corresponds to a relative sea level rise that shifts the shoreline (depositional coastal break) toward the continent, what increases the space available for sediments (increasing of accommodation). This implies that during the stability period of relative sea level occurring after the marine ingression, the shoreline and associated coastal deposits move seaward during deposition, without, however, reaching the position they had before the marine ingression creating a sedimentary regression. A set of increasingly important marine ingressions (relative sea level rises in acceleration) and increasingly smaller sedimentary regressions creates a sedimentary interval with a retrogradational geometry (thickening continentward) that geoscientists call " Transgressions ". Since the first marine ingression increment (eustatic paracycle) occurs, the terrigeneous influx becomes, relatively, weaker (in relation to the extent of the shelf), once the shoreline moves to the mainland. During the relative sea level rise there is no deposition. On the contrary, it creates, just, a small erosion, in the pre-existing topography, that forms a ravinment surface. The deposition occurs during the stability period of relative sea level following the marine ingressions, which precedes a new rise, with any relative sea level fall between them. That is why in sequential stratigraphy we speak of eustatic paracycles (relative sea level rises without any relative sea level fall between them) and not of eustatic cycles (relative sea level rises limited between two relative sea level falls that put the sea level lower than the basin edge). In fact, between each eustatic paracycle, as the sediments settle, the shoreline and associated coastal deposits move seaward, without reaching the extreme position they had before the last relative sea level rise (there is a deficiency of terrigeneous influx). What certain geoscientists denominate sedimentary transgression corresponds, in fact, to a set of increasingly important marine ingressions and increasingly smaller sedimentary regressions, which, overall, gives the impression of a continuous continentward displacement of the coastal deposits. Globally, "transgressions" (what most geoscientists call transgression) have a retrogradational geometry. They correspond to a superposition of increasingly smaller sedimentary regressions (progradational intervals), separated by ravinment surfaces. These surfaces underline relative sea level rises with an increasingly amplitude (accelerating rises) before a significant fall of the relative sea level occurs. As illustrated in this tentative interpretation of a Canvas auto-trace of a seismic line from the Borneo East offshore, from the geometry of the green coloured reflectors (collectively transgressive interval whose thickness increases continentward), the ravinment surfaces can be, easily, deduced. The progradation of the sediments that fossilize the ravinment surfaces are not visible on this auto-trace due to seismic resolution. However, they are, perfectly, observed in the wells' cores taken on this geological interval. In the terminology used in this glossary: 1) A "Sedimentary Regression" is a sequence-paracycle, generally, formed by one or more sedimentary systems tracts, during which the shoreline and the associated coastal deposits move seaward (generally without aggradation, i.e., without upbuilding) ; 2) "Sedimentary Regressions" is the set of increasingly important sedimentary regressions, which collectively have a progradational geometry ; 3) "Sedimentary Transgressions " is the set of increasingly important marine ingressions and increasingly smaller sedimentary regressions, which collectively have a retrogradational geometry.

(*) Local sea level, referenced to any point on the Earth's surface that can be the sea floor or the base of sediment and which is the result of the combined action of the or eustatic level, which is global and referenced to the Earth's centre, and tectonics (subsidence or uplift of the sea floor).

(**) One can speak of marine transgression to designate an advance of the sea on the continent. In this case a marine transgression (passing beyond) is synonymous with marine ingression (enter in). However, one can not speak of sedimentary transgression, since no sediment transgresses the continent. Within a stratigraphic cycle, whether it is a continental encroachment cycle or a sequence-cycle, all sequence-paracycles, which form them, are progradational intervals that correspond to sedimentary regressions.

Inland.............................................................................................................................................................................................................................................Terre ferme

Onshore (em Terra) / En Tierra / Onshore, An Land / 陆上 / Материк (суша) / A terra /

Ground upward of the coastline not covered by sea-water. Opposite to offshore, i.e., the land covered by seawater. Synonym with Onshore and On Land.

See: « Shoreline »
&
« Onshore »
&
« Supercontinent »

This figure shows a part of Angola's inland (onshore) i.e., a part of the land upstream of the shoreline, at the latitude of the Kwanza geographical basin, which is located south of the Congo River and crossed by the Kwanza River (south of Luanda, which is the capital of Angola). This inland or onshore area, as the large majority of English-speaking geoscientists say is, at the geological point of view composed of several basins of the classification of the sedimentary basins of Bally and Snelson: (i) A Precambrian basement ; (ii) A Paleozoic flattened mountain folded belt ; (iii) Rift-type basins formed during the lengthening of the small supercontinent Gondwana (probably in association with a thermal anomaly) and (iv) A post break-up Atlantic-type divergent margin deposited over the rift-type basins formed before the break-up of the lithosphere, that individualized the African and the South American plates. The offshore, that is, the land covered by sea-water (downstream of the coastline), is formed by the central and distal part of the divergent margin (Atlantic type) deposited over the volcanic crust. The volcanic crust can be oceanic or sub-aerial (SDRs or seaward dipping reflectors that correspond to lava flows implemented, immediately, after the break-up of the lithosphere, i.e., they postdate the formation and filling of the rift-type basins). In geological terms, the distinction between onshore and offshore is important because, in general, they are formed by rocks belonging to different sedimentary basins. Offshore consists, essentially, of Atlantic-type divergent margins (developed in areas where prevailing tectonic regimes are extensional and formed in association with the formation of new oceanic crust) or by non-Atlantic divergent margins. The non-Atlantic divergent margins develop in areas where compressional tectonic regimens are predominant, i.e., in association with the megasutures* formation, that is, Earth's moving regions. These regions, which correspond to folded and faulted mountain ranges, testify the complexity of the accretion and deformation phases undergone by the geological bodies in the regions where the compressive tectonic regimens are predominant. However, although the compressional tectonic regimes associated with the subduction zones are predominant in the formation of a megasuture, extensional regimes and the formation of sedimentary basins play, also, an important role. Inland, besides the Precambrian cratons, which occupy most of the onshore, the most common sedimentary basins are: (a) Rifle-type basins ; (b) Cratonic basins and (c) Those associated with the formation of convergent margins such as: Forearc Basins, Foreland basins, Folded belts, etc. In the offshore, sedimentary basins are, often, associated with the formation of new oceanic crust. The different types of subsidence, are the basis of the classification of sedimentary basins proposed by Bally and Snelson (1980), in which the basins associated with the formation of megasutures can be: A) Perisutural (located in the periphery of megasuture): a.1) Oceanic trenches, created in association with a Type-B subduction zone (Benioff) ; a.2) Foreland or foredeep basins, created in association with an A-type subduction zone (Ampferer) and a.3) Chinese-type Basins, associated with felsic intrusions and B) Episutural, formed within the megasutures, which may be: b.1) Forearc basins ; b.2) Backarc basins ; b.3) Pannonian basins ; b.4) Mediterranean basins ; b.5) "Great-basin" type basin and b.6) Californian-type basins. The Bally and Snelson, as well as all other basin classifications, does not allow predicting the volume of hydrocarbons generated and preserved in the different sedimentary basins considered. However, it allows and to a certain degree, it obliges geoscientists to make geological observations controlled by Plate Tectonics, which is the basis of any progress in petroleum exploration. This means that use of this classification in combination with a sequential stratigraphic interpretation of seismic lines, has immediate results in the evaluation of the remaining hydrocarbon potential of geographic depocenters, particularly when structural hydrocarbon exploration is mature or over-mature, as is the case in many areas. Such a combination allows a better evaluation of different petroleum parameters and the recognition of potential non-structural traps as well as quickly highlight the main petroleum parameters and the killer parameters, which alone can, decide the future of a basin or prospect (on the hydrocarbon exploration view point).

(*) Earth's mobile region (folded and faulted mountain ranges) that testify the complexity of the accretion and deformation phases undergone by the geological bodies in regions where the compressive tectonic regimens are predominant. The term megasuture was first used by A. Bally (1975). Although the compressive tectonic regimes associated with the subduction zones are predominant in the formation of a megasuture, extensional tectonic regimes and the formation of sedimentary basins play, also) an important role.

Inlandsis..........................................................................................................................................................................................................................................Inlandsis

Inlandsis (manto de gelo) / Inlandsis, Calota de hielo, Casquete polar / Eisschild / Inlandsis (冰盖) / Ледниковый купол, покровный ледник / Calotta di ghiaccio /

Ice sheet of great thickness and extension (more than 50,000 km²), such as those covering most of the Antarctic continent and Greenland. An inlandsis is, actually, a large glacier and should not be confused with a ice-sea. The ice of an inlandsis has a significant influence on the variations of the absolute or eustatic sea level which is not the case with a sea of ice, since the ice is less dense than the sea-water and therefore floats.

See: « Glacio-Eustasy »
&
« Absolute Sea Level »
&
« Geodetic Sea Level »

An ice sheet, inlandsis or continental glacier is a mass of glacial ice that covers more than 50,000 km² of land. Ice sheets are larger than ice sea or ice platforms (flat, thick, floating ice mass that forms where a glacier or ice sheet discharges onto the surface of the ocean) and glaciers. Ice masses with an area of less than 50,000 km² are called ice caps, which, typically, feed a group of glaciers. There are currently only two ice sheets or inlandsis, one in Antarctica and one in Greenland. During the last glacial maximum, however, the Laurentian ice sheet covered much of Canada and North America, and the Weichselian ice sheet covered northern Europe. The ice sheet of Patagonia covered the southern end of South America. The Antarctic ice sheet is the name of the polar sheet, which covers most of the Antarctic, which in some places extends to the sea (Southern Ocean) by an ice shelf, like, the Ross ice shelf. The Antarctic Inlandsis, whose thickness reaches about 4,000 m, has an area of 13.3 x 10⁶/ km², an average thickness of 1.8 km and a volume of 24 x 10⁶/ km³. This inlandsis formed like a small ice cap (or several) in the beginning of Oligocene, thickening and thinning, successively, until the Pliocene, when it happened to occupy almost all of Antarctica (to avoid misunderstandings it is good to avoid the expressions forward and retreat of the ice). The maximum extent of ice caps and ice seas (Northern and Southern hemispheres) during the last ice age are today, relatively, well known. Its maximum of expansion was reached, approximately, at the same time, more or less, there are 19 ka, and then the ice began to melt. At present, the retrogradation of the Antarctic ice cap is about 450 km (± 24 m per year). It contributed heavily to the more or less 130 meters of absolute (eustatic) sea level rise post-glaciation. As illustrated in this figure, today the Greenland inlandsis covers more than 80% of the surface area of Greenland. This inlandsis developed, just, after the Pliocene (± 1.6 Ma), but apparently with the advent of the first glaciation, its development was so rapid that it allowed the fossils of the plants that grew in Greenland to be much better preserved than their counterparts in Antarctica. Greenland's inlandsis is much smaller than Antarctica inlandsis. It has a surface of 1.7 x 10⁶/ km², an average thickness of 1.6 km and a volume of 2.7 x 10⁶/ km³. If all the ice in this inland melts, the sea level would rise 77 m (54 m with the isostatic readjustment). During the last glacial age the absolute or eustatic sea level* was lower than today 120 m. The melting of the ice seas has no effect on sea level changes, since the water is denser than ice. The formation of an inlandsis is done under the same principle as that of glaciers. An accumulation of snow resulting from insufficient thawing causes a compression of snow that expels air that it contains and turns into ice. This ice is, sufficiently, plastic to deform by gravity or its own weight. In the case of the inlandsis is the weight of the ice causes it to move by flow downdip. At the scale of continent or of large island, the dip is too low to cause a flow by gravity. A balance between snow fall, ice weight and snow ablation (sublimation, melting, iceberg formation) occurs when the mass of ice stabilizes its thickness and extent. An inlandsis is held more by a weak ablation than by a snow input. During the summer, melting ice water flows under a glacial cap (pressure favours melting) transporting fine suspended rock particles (rock flour) that are deposited in front of the ice. The reactivation of such deposits by katabatic winds (which carries high density air from an elevation down the slope due to the action of gravity) disperses the sediments into loess. Loess deposits are known in North America, Central Europe, Siberia, China, and Patagonia. Its thickness varies. It can reach 150 meters (China). Loess does not remain in dust. Loess wet by rain compacts under it's own weight. The wet loess is impermeable, and so the top layer protects the layers below when it rains.

(*) Supposed global and referenced to the Earth's centre or to a satellite contrasts with the relative sea level, which is local and referenced to any point on the Earth's surface, which can be the seafloor or the base of the sediments.

Inner Neritic...................................................................................................................................................................................................Néritique interne

Nerítico interno / Nerítico interno / Inner neritischen / 内蒙古浅海 / Неритический (внутренне) / Neritico interno /

Marine sub-environment characterized by a water-depth between 0 and 20 meters.

See: « Outer Neritic »
&
« Neritic »
&
« Shefal Accommodation »

In this diagram the neritic province is distinguished (water-depth between 0 and 200 meters) and the oceanic province or blue sea. The first corresponds, more or less, to the continental shelf (between the shoreline and the platform edge, which may or may not correspond to the edge of the basin) and to the surface of blue sea area, that is, up to 200 meters deep. In certain geological conditions (lowstand conditions), when the basin does not have a continental shelf (shoreline, more or less, coincident with the continental edge), the neritic zone corresponds just to the surface horizon of blue sea. As shown above, the neritic zone is, generally, divided into three sub-environments: (i) External Neritic Zone, characterized by a water-depth between 100 and 200 meters ; (ii) Medium Neritic Zone, with a water-depth between 20 and 100 meters and (iii) Internal Neritic Zone, which is characterized by a water-depth between 0 and 30 meters. In the neritic zone, some geoscientists distinguish between a zone of transition between 0 and 5 meters of water-depth, that is, the brackish water domain (bays, lagoons, etc.) and the non-marine deposition zone (continental, fluvial, etc.). The outer neritic zone is, in general, a sector of low sedimentation rate. The upper part is part of the photic zone, but in the bottom part, the penetration of sunlight is insufficient for life develops from photosynthesis (life that uses solar energy to convert carbon dioxide, into water and food). In the internal neritic zone, between the shoreline and about 20 meters deep, i.e., approximately, to the depth of influence of the waves (rough sea), the predominant sediments are rich in sand and the rocks, which are formed by diagenetic and meteoric changes are, generally, thick and with high porosity and permeability. In other words, they are excellent reservoir-rocks. The shaly sediments, deposited in association with the flooding surfaces, form excellent sealing-rocks (high displacement pressure or poor permeability). The alternation of reservoir-rocks and sealing-rocks creates favourable conditions for the formation of non-structural traps for hydrocarbons.

Inselberg (Monadock)....................................................................................................................................................................................................Inselberg

Inselbergue / Inselberg / Inselberg (Ein kleiner Hügel oder Berg) / Inselberg （一个小山坡或山） / Останец выветривания / Monadnock, Inselberg /

A prominent and steep hill formed by hard and consistent rocks, rising, abruptly, from a low relief plain (Whittow, 1984). Inselbergs are characteristic of tropical landscapes, particularly, savannah areas, such as the famous Pão de Açúcar in Rio de Janeiro (Brazil). In the Namibia desert, which is very arid, granite inselbergues hundreds of feet high are very common.

See: « Granite »
&
« Desert »
&
« Monadnock »

In the tropical erosion plains, the important reliefs, with abrupt slopes, which are not connected with the surface of the peneplain, are the inselbergs. This term derives from German and means mountain island ("insel" and "berg") and was used for the first time by the German explorers to designate the isolated hills (granitic or not), that protrude from the plains of South Africa. Many inselbergs are geological relics. They retained their relief, while surrounding areas were eroded by erosion agents, which is corroborated by the presence of pediments (erosion surfaces that many geoscientists confuse with alluvial fans) at the base of many inselbergs. The occurrence of inselbergs implies variations in the rate of degradation of the terrestrial surface. Inselbergs are one of the paleo-forms that can survive, with little modification, for tens of millions of years, since in these landscapes the active processes of erosion are limited to the bottom and walls of the valleys. An inselberg does not necessarily have a rounded top, such as the Sugar-Loaf Mountain in Rio de Janeiro. They can have several profiles: (i) Inselberg in Sugar-Loaf Mountain with over-lining slopes ; (ii) Inselberg in Classic Sugar-Loaf ; (iii) Inselberg in dissymmetrical Sugar Loaf ; (iv) Inselberg with a dominant Sugar Loaf in a sea of hills of the equatorial type ; (v) Top Plane Inselberg (testimony of a peneplain) ; (vi) Inselberg with Irregular Top ; (vii) Inselberg with Pediment and (viii) Massif in Inselberg, as shown in this figure (Mulanje Granite Mountain in southern Malawi). For French geomorphologists an inselberg is: (i) A steep residual rocky terrain or (ii) A miniature mountains isolated from rocky massif on limestone slopes or on crystalline rocks in tropical climates.

Inshore (Backshore)...............................................................................................................................................................................................Arrière-plage

Antepraia / Anteplaya / Hinterstrand /后滨 / Отбрежье (верхняя береговая терраса) / Indietro spiaggia /

Coastal zone, generally, dry and, relatively, narrow between the highest line of the equinox tides (lower boundary) and the upper part of the coastal process zone, i.e., the base of the cliff (escarpment). The backshore (inshore) is covered by water only during storms and high tides. The geometry of the backshore is, generally, sub-horizontal or slightly inclined continentward. The crest of the berm further downstream separates the backshore from the shoreface.

See: « Berm-Ridge, Storm Beach »
&
« Beach »
&
« Cilff »

Many coastal zones, especially those that have a siliciclastic lithology, exhibit a morphology similar to that illustrated in the geological section of this figure. The area with more or less concave geometry, between the high-tide line and up to a depth of 5-20 m, is the foreshore, which encompasses the intra-tidal beach and the submarine beach. Downstream from the foreshore, the sea floor forms a ramp, which slopes gently towards the continental edge, which in this case corresponds to the platform's edge. In the foreshore, there are bars and lows induced by the surf of the waves. The inter-tidal beach lies between the high-tide and low-tide lines, while the backshore extends between the high-tide line and the beginning of the dunes. In the backshore there are one or several berms that look like small terraces with small slopes on the sea side. When a relative sea level rise (combination of absolute or eustatic sea level* and tectonics), the morphology of the beach largely determines the value of the continental encroachment, that is, the value of the horizontal component of the coastal aggradation. If the beach morphology is, relatively flat, a relative sea level rise of about 10 m will shift the depositional coastal break of the depositional surface (roughly the shoreline) several kilometers upstream. On the contrary, if the beach morphology is relatively sloping seaward, the same relative sea level rise will shift the depositional coastal break of the deposition surface (and associated deposits) landward just tens or hundreds of meters. As the relative sea level falls, the displacement to the seaward and downward from the depositional coastal break of the depositional surface is also a function of the morphology of the foreshore and the ramp. In sequential stratigraphy, it is always important to calculate the value of the vertical and horizontal component of the coastal aggradation in order to determine the morphology of the coast and particularly the morphology of the beaches. Note that backshore, foreshore and longshore (offshore) is one of many divisions of coastal morphology found in scientific literature. As each country, not to say each geoscientist, tends to use its own divisions and its own terminology, it is important not to forget the bibliographical reference of the terms used.

(*) Global sea level referenced to the centre of the Earth or to a satellite and which is the result of the combined action of: (i) Tectono-eustasy (controlled by volume variation of ocean basins) ; (ii) Glacio-eustasy (controlled by the variation of ocean water volume) ; (iii) Geoidal-eustasy (controlled by the distribution of ocean water caused by variations in the terrestrial gravity field) and (iv) Thermal expansion of the oceans or steric sea level rise.

Internal Convergence...............................................................................................................................................................Convergence interne

Convergência interna / Convergencia interna / Interne Konvergenz / 内部收敛 / Внутреннее схождение / Convergenza interno /

Geometry in which strata, or seismic reflectors, converge thinning sideways toward the basin. This type of geometry, which can develop anywhere within a sequence-cycle, should not be confused with onlaps along unconformities.

See: « Stratigtraphic Cycle »
&
« Relative Sea Level Change »
&
« Reflection Configuration »

As can be seen on this tentative geological interpretation of a Canvas auto-trace of a detail of a Gulf of Mexico seismic line, the internal configuration of the seismic intervals, particularly the coloured intervals in light brown tones, does not converge towards the basin (nor at the moment of deposition). The vast majority of these intervals increase in thickness to SSE and not to NNW. You can say that the internal configuration of these interval is, currently, divergent for SSE. The lower terminations of the reflectors of these intervals can not be considered as downlaps. The thickness of a sedimentary or seismic interval between two consecutive downlaps begins to increase towards the basin, reaches a maximum thickness and then decreases in thickness until it disappears by pinchout in the distal part of the basin. This is not what we see in the seismic intervals considered on this tentative interpretation. In this example, the reflector terminations of these interval correspond to onlaps which later, i.e., after deposition, were tilted (inclined) seaward. This inclination developed as the underlying salt horizon (coloured in dark violet) flowed, laterally, in such a way that the onlaps became apparent downlaps. Surprisingly, for many years, the original seismic line of this tentative interpretation was used by many geoscientists to illustrate, within the post-Pangea transgressive phase of the continental encroachment cycle, the progression of the basin edge of the continental encroachment subcycles during the Cretaceous. Such use corresponded to a scientific verificationist * approach that many geoscientists, wrongly, adopted in the geological interpretation of seismic lines and particularly, in the Gulf of Mexico. A falsificationist or critical scientific approach has, clearly, shown that the a lower termination of the reflectors corresponded to apparent downlaps and the apparent downlap surface visible at about 6 s (t.w.t. or double time) does not correspond to an unconformity. It underlines a tectonic disharmony between the infra and suprasalt intervals, induced by the lateral flow of the saliferous horizon, which can still be seen at the ends of this tentative interpretation (coloured intervals in dark violet). In fact, it is very likely that during the Cretaceous, in the area where a salt suture (salt window or salt thickness below seismic resolution) is observed today, there was a salt swelling that was, gradually, fossilized by the onlapping of the overlying sediments, whose deposition contributed to the lateral outflow of the salt, which created a compensatory subsidence. The other types of internal configurations found, frequently, on the seismic lines are: (i) Parallel Configuration, the seismic reflectors are parallel to each other ; (ii) Subparallel Configuration, reflector undulations are visible within a parallel configuration ; (iii) Tangent/Oblique Configuration, reflectors have a decreasing slope toward the base ; (iv) Parallel Wavy Configuration, the reflectors are corrugated, but parallel to each other; (v) Divergent Configuration, the reflectors thicken, laterally, basinward ; (vi) Parallel Oblique Configuration, the reflectors have a parallel / oblique pattern and they terminate downstream with a significant slope ; (vii) Convergent Configuration, the reflectors taper, laterally, basinward ; (viii) Sigmoid Configuration, the reflectors have a geometry of an S upside down ; (ix) Sigmoid / Oblique Complex Configuration, which is a particular case of the sigmoid configuration, in which the inclination of the middle part of the progradations is very strong and the presence of toplaps, by truncation, is frequent ; (x) No Reflections Configuration, absence of reflections ; (xi) Mounded Configuration, the reflectors form topographic anomalies above the base level, as in organic and volcanic constructions ; (xii) Shingled Configuration, the reflectors are oblique and almost lying on top of each other ; (xiii) Chaotic Configuration, the reflectors are arranged in a disorderly manner ; (xiv) Mammary Configuration, the reflectors have, overall, a nipple shape and (xv) Fill Configuration, the reflectors fill negative topographic anomalies of the underlying layers.

(*) The scientific procedure proposed by Popper is of the type "modus tollens" (process that denies in denying or denying the consequent): (i) Hypothesis → consequence ; (ii) The consequence is not corroborated ; (iii) Therefore, the hypothesis is falsified. A theory or hypothesis can never be verified, it can only be refuted. Such a refutationist or falsificationist perspective is Sir K. Popper's greatest criticism of the inductive procedure characteristic of the verificationist method (in spite of a large the number of particular observations, there is no logical justification for its generalization in all cases).

Internal Platform (Inner shelf).............................................................................................................................Plate-forme interne

Plataforma Interna / Plataforma interna / Interne Plattform / 内部陆架 / Внутренняя платформа / Piattaforma interna /

Sub-environment of a continental shelf characterized by a water-depth between 0 and 30 meters, in other words, the part of the continental platform (shelf) adjacent to the coastline.

See: « Eustatic Sea Level »
&
« Continental Platform »
&
« Highstand »

When a basin has a continental shelf, which is not always the case, certain geoscientists distinguish the platform adjacent to the shoreline, which they call the internal platform and which is characterized not just by a water-depth between 0 and 30 meters, but also by a very typical biota. Indeed, within a continental shelf three areas can be evidenced: (i) Internal Platform, between 0 and 30 meters of water-depth ; (ii) Middle Platform, between 30 and 70 meters of water-depth and (iii) External Platform, between 70 and 200 meters of water-depth. On the other hand, taking into account the displacement of fish larvae, certain geoscientists consider, preferentially, three depth zones on a continental shelf: (a) Between 0 and 20 meters ; (b) Between 20 and 40 meters and (c) Between 40 and 70 meters. Within a stratigraphic cycle, sequence-cycle (induced by a 3^rd order eustatic cycle, which means that its time-duration varies between 0.5 My and 3-5 My), a sedimentary basin has no platform during the deposition of the lowstand systems tracts group (LSTG), within which, when complete, from bottom to top, three subgroups can be recognized: a) Submarine basin floor fans (SBFF) ; (ii) Submarine slop fans (SSF) and (iii) Lowstand prograding wedge (LPW). The basin begins to have a continental shelf since the first flooding surface, which marks the beginning of the deposition of the highstand systems tracts group (HSTG). This is particularly true to the transgressive interval (IT), which is the lower systems tracts subgroup. In fact, as the sea level floods the coastal plain of the underlying lowstand prograding wedge, the shoreline is displaced continentward (marine ingression). As the relative sea level rises, in acceleration*, during the transgressive interval, the dimensions of the continental shelf increase as well as the water-depth. After each increment of the marine ingression, more or less, important stability periods of the relative sea-level occur during which increasingly smaller sedimentary regressions deposit developing a transgressive interval (IT) with a retrogradational geometry. The transgressive interval (IT) of a sequence-cycle is nothing more than a vertical stacking of smaller and smaller sedimentary regressions, which, globally, displace the shoreline continentward. Since the relative sea level begins to rise in deceleration, i.e., from the beginning of deposition of the highstand prograding wedge (HPW), the continental shelf dimensions begin to decrease. The shoreline begins to shift seaward in a more or less continuous way. During the 1^st stage of development of the highstand prograding wedge (HPW), the basin has a continental shelf. However, since a given a point, the continental shelf is fossilized by the highstand prograding wedge and disappears. At that moment, the shoreline becomes (mainly in the seismic lines and having into account the seismic resolution) the new continental edge (which is also the basin edge). It is from this moment that begins to deposit the second stage of development of the highstand prograding wedge, since the basin has no more continental shelf. As from this moment on, the shoreline is the new basin edge, the outer limit of the coastal plain, which corresponds to the coastline emphasizes, also, the continental edge. In the internal platform, which corresponds to the part of the continental shelf adjacent to the shoreline, the different larvae of fish that occur there form groups that, as said above, can be used to determine how the larvae move to the areas where they will grow depending on the water-depth.

(*) Relative sea level is a local sea level, referenced either the sediment base or any other point on the land surface, such as the sea floor and which is the result of the combined actio0n of sea level absolute or eustatic and tectonics. A relative sea level rise in acceleration means that the increments of a marine ingression are increasingly important. In the same way since the increments of the marine ingression are increasingly smaller, the relative sea level rises in deceleration. It is very important to consider the increments of a marine ingression, since an absolute or relative sea level rise is not done in continuity, but in stages. The relative sea level rises, stabilizes, rise again, stabilizes, and so on, until a significant relative sea level fall occurs moving the shoreline seaward and downward, creating an erosional surface that limits the sequence-cycle. It is during the stability periods of relative sea level that deposition occurs.

Interregional Unconformity (Sloss)......................................................Discordance interrégionale (Sloss)

Discordância inter-regional / Discordancia inter-regional (Sloss) / Interregionale Diskordanz / 区域间的不整合 / Межрегиональное несогласие / Discordanza interregionale /

Unconformity that can be mapped throughout a sedimentary basin and that can sometimes be recognized in other basins. This type of unconformity was for the first time recognized in the North American cratonic basins (Sloss).

See: « Unconformity »
&
« Global Unconformity »
&
« Sequential Stratigraphy »

In sequential analysis, it is essential to recognize and map the unconformities, that is, the erosional surfaces created by significant relative sea level* falls, which is local and referenced to a point on the Earth's surface, which may be the sea floor or the base of the sediments (top of continental crust). In general, interregional unconformities can be followed to the full extent of a sedimentary basin and even in different basins. As schematised in this figure, in the centre of the basins, obviously inter-regional unconformities are very difficult to bring to light, at the basin borders, since the erosional surface may not exist. The unconformities must be differentiated from the discontinuities (stratigraphic surface created by a period of time without deposit or by erosion is no longer evident and becomes a correlative correlation). The vast majority of geoscientists reserve the term unconformity for erosional surfaces induced by significant relative sea level fall, regardless of the importance of the eustatic or tectonic component. Erosion has to be regional rather than local. In the same area, we can not have erosion and deposition at the same time. An exception is possible in the deep parts of the basin in association with turbidite depositional systems (submarine basin floor fans and, more rarely, submarine slope fans). For certain geoscientists, even in these conditions of great water-depth, erosion is almost always local. In a meander, for example, deposition and local erosion exist side by side, which means that they are contemporary. There is erosion in the concave bank and deposition of the convex bank, in which the point bar is deposited. In general, erosional surfaces associated with a meander can not be considered as unconformities since they are not, in most cases, associated with significant relative sea level falls. Although, by definition, inter-regional unconformities can, in general, be mapped along a sedimentary basin and sometimes even recognized in several basins, they are more evident in the border of the sedimentary basins than in the centre where the intervals are thicker. This is why tentative interpretations of seismic lines can, often, be made at the hierarchical level of sequence-cycles in the basin borders, where the geometric relationships between seismic reflectors are better marked. In the central part, in general, they are made at the hierarchical level of the continental encroachment sub-cycles. Although an unconformity always limits a stratigraphic cycle. Its identification is not always easy, especially, if it is not tectonically enhanced. What many geoscientists call angular unconformity is just a tectonically enhanced unconformity. At the scale of a geological maps or regional seismic line, a tectonically enhanced unconformity goes sideways, almost always, to a "normal" or "cryptic" unconformity that many geoscientists call eustatic unconformity to underline the fact that the eustasy (absolute or eustatic sea level changes) is responsible for sedimentary cyclicity and not the tectonics. On this subject there is no consensus, particularly in certain sedimentary basins such as foreland basins, where the rate of tectonic changes may be of the same order of magnitude as the rate of absolute sea level changes. There are only two regions where unconformities not tectonically enhanced, that is, cryptic unconformity (or eustatic unconformity) are relatively easy to identify: (i) Downstream of the basin edge, where the onlapping of the lowstand deposits (lowstand prograding wedge and submarine fans ) are very visible and, in particular, near the base of the continental slope, due to the onlapping of the submarine basin floor and slope fans and (ii) In the upper part of the continental slope, where the filling of submarine canyons emphasize the basal unconformity of the overlying sequence-cycle ; (iii) Upstream of the basin edge, when incised valleys fills are present the unconformities dislocations can be recognized locally.

(*) Relative sea level is the result of the combined action of tectonics (subsidence or uplift of the sea floor) and absolute or eustatic sea level, which is supposed to be the global and referenced to the Earth's centre (using a radar satellite).

Interthem...............................................................................................................................................................................................................................Interthème

Intertema / Intertema / Interthem (zwischen zwei Diskordanzen) / Interthem（两种不整合） / Интертема / Interthem (tra due discordanze) /

Minor unconformity limiting a stratigraphic unit with a thickness comparable to that of a geological formation or comparable to the time and thickness of a geological stage. Several interthems can be recognized within a synthem. A synthem is a discordant sedimentary interval limited between two type I or type II unconformities, but it does not correspond to the sequence-cycle, since a sequence-cycle is limited by two consecutive unconformities (between 0.5 and 3-5 My) and by their correlative paraconformities in deep-water, which is not the case of a synthem.

See: « Unconformity »
&
« Synthem»
&
« Stratigtraphic Cycle »

Since the advent of sequential stratigraphy, the terms interthem and synthem (discordant interval limited by type I or II unconformity) have fallen into disuse. The meaning of the terms minor and major unconformity are relative. They are dependent on the time scale considered. When it is recognized in the field, that is, in an outcrop, an unconformity (erosional surface induced by a significant relative sea level *fall, it may be a minor or even an invisible unconformity (cryptic) in a regional seismic line. In a conventional seismic line, taken in an area with a normal sedimentation rate (such as 8 m every 100,000 years), it is difficult to recognize the unconformity separating the stratigraphic cycles called sequence-cycles (stratigraphic cycles induced by 3^rd order eustatic cycles, whose time-duration varies between 0.5 and 3-5 million years). These unconformities can be considered interthems. They separate stratigraphic units with a thickness comparable to the thickness of the geological formations. It may be said, in general, an interthem corresponds to a unconformity that limits a sequence-cycle, whereas a synthem corresponds to an unconformity that limits a continental encroachment subcycle (stratigraphic cycle induced by a second order eustatic cycle, whose time-duration varies between 3-5 My and 50 My). In this tentative geological interpretation of a Canvas auto-trace of a detail of a North Sea regional seismic line, all the unconformities of the Late Jurassic and Early Cretaceous can be recognized by the reflector terminations (onlaps, downlaps and toplaps) and the identification of onlapping and downlapping seismic surfaces. It is surprising to note that some geoscientists continue to forget, in their models, the long periods of calm during which nothing happens. In most stratigraphic sections, hiatus (erosional or by no deposition) are, generally, greater than the total duration of effective deposition of the preserved sediments. Certain deposits, such as fluvial deposits and, particularly, overbanking deposits, have a, relatively, poor preservation. They are deposited above the base level. On the contrary, turbidite deposits, which are, usually, deep-water deposits (turbidite deposit can, also, be found in lacustrine environments), emphasize episodic geological events. They have an excellent preservation because they are deposited, below the base level. On this tentative interpretation, which was calibrated, in geological terms, by the exploration well results, the age difference between two consecutive unconformities (for instance, between SB. 138 Ma and SB. 128.5 MPs) is always less than 3-5 My, i.e., they limit sequence-cycles (SB. stands for stratigraphic boundary). It is interesting to note, on this tentative interpretation, that the distal part of the interval limited by the unconformities SB. 138 Ma and SB. 158.5 Ma, which corresponds to the Middle/Late Jurassic, emphasizes the downlap surface with which are associated the marine source-rocks of almost all the North Sea oil fields. Effectively all Early Cretaceous sequence-cycles, i.e., SB. 138 Ma/SB.136 Ma ; SB. 136 Ma/SB. 135 Ma ; SB. 135 Ma/SB. 134 Ma ; SB. 134 Ma/SB. 131.5 Ma ; SB. 131.5 Ma/SB. 129 Ma and SB. 129 Ma/SB. 128.5 Ma end by downlaps over the Jurassic interval SB. 158.5 Ma/SB. 138 Ma, which includes sediments whose age ranges from the Callovian to the Tithonian. The DS. 91.5 Ma (downlap surface) corresponds to the eustatic peak of the absolute (eustatic) sea level, which is referenced to the Earth's centre, with which are associated many marine source-rocks the Atlantic offshores. However, in this area, the organic matter of rocks associated with this seismic surface did not reach the oil window. At the top of this interpretation attempt, the unconformity SB. 30 Ma, which is, easily, recognized in all the regional seismic lines of the Atlantic divergent margins, in particular, by the filling of the submarine canyons created by the eustatic sea level fall, which many geoscientists consider as the first consequence of the initiation of the formation of the Antarctic Inlandsis.

(*) Local sea level, referenced to any point on the Earth's surface, which can be  the bottom of the sea or the base of the sediments (top of the continental crust) and which is the result of the combined action of absolute (eustatic) sea level (supposed global sea level referenced to the Earth's centre) and tectonics (subsidence or uplift of the sea floor).

Interthem (Minor unconformity)...............................................................................................................................Discordance mineure

Discordância menor / Discordancia menor / Kleine-Diskordanz / 轻微差异 / Меньшее несогласие / Discordanza minore /

Unconformity limiting a stratigraphic unit with a thickness comparable to that of a geological formation or comparable to the time and thickness of a geological stage. Several smaller unconformities can sometimes be recognized within a synthem (discordant interval, i.e., limited sedimentary interval between two type I or type II unconformities).

See: « Interthem »
&
« Lithostratigraphic Unit »
&
« Synthem »

The Indonesia offshore and, particularly, the Kalimantan offshore (Borneo) corresponds to the stacking of three types of basins (classification of the sedimentary basins of Bally and Snelson, 1980) of different age, which from the bottom to top are: (i) Mesozoic Folded Belt or Precambrian Basement ; (ii) Mesozoic/Cenozoic Backarc Basin, in which two tectonic phases can be recognized: a) Rifting Phase, characterized by a differential subsidence and b) Sag or Thermal Phase, characterized by thermal subsidence and (iii) Non-Atlantic Type Divergent Margin of recent age, which has formed since the break-up of the lithosphere, within the backarc basin, occurred, which created a marginal sea (South China Sea). On this tentative geological interpretation of a Canvas auto-trace of a detail of an offshore seismic line (East of the island of Borneo), three stratigraphic cycles called sequence-cycles (stratigraphic cycles induced by 3^rd order eustatic cycles, i.e., eustatic cycles with a time-duration ranging between 0.5 to 3-5 My) can easily be highlighted. These stratigraphic cycles are limited by unconformities (SB 8.2 Ma, SB 6.2 Ma and SB 5.5 MS), which were created by significant falls of the relative sea level (local sea level, referenced to the bottom of the sea or of the base of the sediments, that is. to the top of the continental crust), which put the sea level lower than the basin edge. The coastal onlaps were abruptly displaced to the seaward and downward (negative aggradation). Each of these unconformities was dated using the micro-paleontological studies of well cored and the chronostratigraphic chart (Haq et al., 1986). The wells in this region never reached the submarine basin floor fans associated with unconformities, which allow them to date it, more or less, correctly. The age of the pelagic layer, deposited between the submarine basin floor fans, which gives, indirectly, the correct age of unconformity, i.e., the age of the relative sea level fall, since it underlines the minimum hiatus between the sediments underlying and overlying the unconformity. As the age difference between the unconformities SB. 8.2 Ma, SB. 6.2 Ma and SB. 5.5 Ma is always less than 3-5 My and greater than 0.5 My, the limited sedimentary intervals were, conventionally, induced by 3^rd order eustatic cycles and thus can be considered as sequence-cycles . Within the sedimentary intervals that they define, that is, within these sequence-cycles, whose sedimentation rate is very high, there are unconformities, which certain geoscientists call minor unconformities*, which allow to consider stratigraphic cycles of lower hierarchy, which are, probably induced by 4^th or 5^th order eustatic cycles (timer-duration between 0.01 My and 0.5 My). Some of these stratigraphic cycles, which many geoscientists call high-frequency or interthems, since the associated relative sea-level changes are very rapid, are complete. In this case, they are composed of all the systems tracts groups and sub-groups that form a sequence-cycle, which from top to bottom are : (A) Highstand Systems Tracts Group (HSTG), which is composed by two subgroups : (A.i) Highstand Prograding Wedge (HPW), whose progradational geometry is very well marked ; (A.ii) Transgressive interval (TI), whose geometry is globally, retrogradational and sub-horizontal and (B) Lowstand Systems Tracts Group (LSTG). which is generally formed by three sub-groups (from top to bottom): (B.i) Lowstand Prograding Wedge (LPW) with a progradational geometry ; (B.ii) Submarine Slope Fan (SSF), with the characteristic gull-wing structures of P. Vail and (B.iii) Submarine Basin Floor Fans (SBFF), with a parallel aggradational geometry. The submarine basin floor fans may be disconnected or not from the break at the base of the continental slope. In the first hypothesis, they can be, directly, fossilized by the progradations of the lowstand prograding wedge or even by the late progradations of the highstand prograding wedge. When these high frequency cycles are incomplete, they are usually formed just by lowstand systems tracts sub-groups.

(*) This denomination is, certainly, due to the fact that these unconformities are not indicated in the EPR (Exxon's Exploration Petroleum Research) chronostratigraphic charts.

Intertidal Beach (Foreshore)................................................................................................................................................Plage intertidale

Praia intramareal (entre marées) / Playa intramareal (entre mareas) / Wattenmeer / 潮间带 / Береговая полоса, затопляемая во время прилива / Piano mesolitorale /

Morphogenic range of a beach bounded between low and high tide. It corresponds to the "beach" of certain geoscientists (G. S. de Carvalho, 1973) and to the proximal part of the shoreface of Anglo-Saxon geoscientists (S. Judson and S. Richardson, 1995).

See: « Shoreface »
&
« Littoral »
&
« Karst »

The intra-tidal beach of the Anglo-Saxon geoscientists corresponds to the morphogenetic tract of a beach, which the great majority of European geoscientists call the nearshore, and which they define as the part of the beach that extends in the space reached by the swash currents, between levels of neap high and low tides. The intratidal beach corresponds, roughly, to the intra-tidal zone, which American geoscientists call "foreshore" or "nearshore", i.e., the area that is exposed to the air during low-tide and submerged during high-tide or, the area limited between the tide lines. The intra-tidal beach may include different habitat types, either steep rocky cliffs, sandy beach or salt flats. The intratidal beach may be narrow, as is the case in almost all the Pacific Ocean islands, since the difference in tidal amplitude is very small. It can also be very wide, when a little sloping beach interacts with a high-tide of great amplitude (as in the case of a important relative sea level rise on a little inclined substrate). Geoscientists divide the inter-tidal area into three zones: (i) Low ; (ii) Middle and (iii) High, depending on the average exposure of the area. The low inter-tidal zone, which is adjacent to the sub-tidal zone, is only exposed to the air during low-tides and therefore, it is, essentially, a marine area. The middle intra-tidal zone, on the other hand, is, regularly, exposed to the air and submerged during medium tides. The upper intratidal zone is just covered with water during high-tides, which means that for the most part it represents a terrestrial habitat. The high intra-tidal zone is adjacent to the breaking zone (i.e., it is above the highest level of the middle tide level, but still receives the sea-spray of the waves). On the coastlines exposed to a strong action of the sea waves, the inter-tidal zone is influenced by the waves, since the sea-spray extends above the high-tide line.

Isobar.............................................................................................................................................................................................................................................................Isobare

Isóbara / Isobara / Isobare / 安索帕 / Изобара / Isobara /

Line that joins points with the same value of atmospheric pressure (in reference to sea level).

See: « Map »
&
« Middle Sea Level »
&
« Hadley Cell »

As illustrated in this figure, an isobar is a line, on a graph or map, connecting points of equal pressure. In a three-dimensional space that forms the Earth's atmosphere, the isobaric surface lines that connect, at a given instant, the points of equal atmospheric pressure serve to delimit, on analysis and forecast charts, meteorological systems such as: (i) Depressions, i.e., areas where atmospheric pressure, adjusted to sea level, decreases horizontally to a low pressure centre, that is, the minimum local pressure ; (ii) Anticyclones, i.e., atmospheric circulation zones around high pressure centres ; (iii) Barometric Troughs, which are excrescences of depressions (zones of low pressure around an area) and (iv) Barometric Ridges, i.e., elongated regions in the field of atmospheric pressure, where it is maximum in relation to the environment, without being a closed circulation. The direction of rotation of the anticyclones is related to Coriolis force. They rotate clockwise in the northern hemisphere and counter-clockwise in the southern hemisphere. The isobars are, usually, indicated on standard charts at sea level (charts or surface maps). The calculation of the reduced pressure at sea level or that of the pressure at an altitude between sea level and the ground on the same vertical, allows to draw an isobar surface, continuously, even where the associated pressure would be, due to the relief, higher than the soil pressure. When making meteorological charts at altitude, although they can be made in the base of isobar lines at a standardized height, using contour line (isoline, isopleth, or isarithm*), i.e., level curve, which connect points with equal altitude, at pressure levels constant, called isobaric heights. In these cases, certain internationally set pressure values are used, of which the most important are 850, 700, 500, 300 and 200 hPa (1 hPa = 100 Pa) and the isolines represent the height above sea level, where they meet the pressures. Of course, sometimes isobar surfaces, associated with non-standard pressure values are used, such as when calculating or exiting a numerical time prediction model.

(*) Line drawn on a map or chart to connect points having equal numerical values.

Isobath (Isobathymetric)................................................................................................................................................................................................................Isobathe

Isóbata / Isobata / Isobathe / 等深线 / Изобата / Isobata /

Line that joins points with the same depth, in meters, either in the bathymetric charts, either in time, as in the seismic maps, in particular in the seismic horizons maps used in the petroleum exploration.

See : « Isochron »
&
« Seismic Line »
&
« Contour Map »

In oil exploration and especially in the offshore, the maps in isobaths are the most frequent, since the vertical scale of the seismic lines (migrated or not) are in time (double time) and not in depth. All depth-isobath maps of seismic horizons are made from time-isobath maps at (which certain geoscientists call isochron maps). The example shown in this figure represents a depth-isobath maps (meters) of the basement in Vietnam offshore. This map was made from a map in time-isobath built from the tentative geological interpretation of seismic lines. Thus, it can be said that in this offshore, the basement highs individualize three sedimentary basins: (i) Mekong Geographic basin, north of the Conson-High ; (ii) South Saigon Geographic Basin and (iii) North Saigon Basin. The Saigon basins are located eastward of the Conson High and are individualized by a basement high between them. In Bally's basin classification, these basins correspond, in fact, to the vertical stacking of different sedimentary basins. From bottom to top, the seismic lines suggest: (i) A basement or a folded belt ; (ii) Rift-type basins, which characterize the lengthening or rifting phase of a back-arc basin ; (iii) Cratonic basin, which characterize the sag (thermal) phase of the back-arc basin and (iv) A non-Atlantic type divergent margin developed over the back-arc basin, when the lengthening behind the volcanic arc causes the break-up of lithosphere and a, more or less, important oceanization, which creates a marginal sea (South China Sea). In time-isobath maps of the seismic horizons it is always necessary, to avoid errors of interpretation not to forget, particularly, in offshore areas, the influence of the water-depth, since structural high points in time may correspond to low structural points in depth maps. An abrupt increasing in water-depth between the shelf and the continental slope, necessarily, slows the seismic waves downstream of the basin edge.

Isobathytherm..................................................................................................................................................................................Isobathithérmique

Isobatitérmica / Isobatitérmica / isobathythermisch Linie / 等温深度线 / Изобатитерма / Isobatitérmic /

Line joining points with equal temperature value, at different depths and in a vertical plane.

See : « Isochron »
&
« Contour Map »
&
« Thermal Flux »

From the scientific point of view, geothermics studies the Earth's thermal regime and the mechanisms of heat transfer*, whether these are conduction or convection. Geothermics attempts to integrate all geological, geochemical and geophysical data into satisfactory models. In addition to thermal variations of external origin that affect, according to their periodicity, some tens of meters of thickness, the temperature of the soil increases with the depth: it is the geothermal gradient. The geothermal degree is the vertical distance to travel so that the temperature rises by one degree Celsius. On average, the geothermal grade is 32 m. The increase in temperature in depth, that is, the Earth's internal heat flow can be used as a renewable energy** (using an inexhaustible source of energy of natural origin, such as solar radiation, winds, water and carbon cycles in the biosphere, the effect of lunar and solar attraction on the oceans, etc.). This figure illustrates the variation of the geothermal degree (degrees Celsius) in the geographic Kwanza basin (Meso/Cenozoic Atlantic-type divergent margin overlying Late Jurassic/Early Cretaceous rift-type basins). The isobathythermal lines allowed to define the variations of the geothermal flow, which is here expressed in degrees Celsius by 100 meters. As illustrated above, a zone between 2.0 and 2.5° C means that the soil temperature increases between 2 and 2.5° C every time the depth increases by 100 meters. This type of map is very important in oil exploration, since it suggests the most likely places where rocks rich in organic matter (potential source-rocks) may eventually become source-rocks, that is, its organic matter reached maturation. In this onshore (Kwanza geographic basin), there are two areas, one in the north the other in south, in which the temperature increase, for every 100 meters of depth, exceeding 3° C. These are the areas where a maturation of organic matter is more likely, at the condition that the potential source-rocks have been sufficiently buried. The presence in this basin of an important salt horizon (good heat conductor) with a variable thickness, can alter the geothermal degree in the overlying rocks.

(*) Heat nor work are not energy forms. Both are methods to transfer energy from one place to another, that is to say, work is a method and heat is another method. As energy can be transferred either through work or heat, physicists conclude energy is conserved in the field of dynamics (movement of individual objects and the reciprocal conversion of kinetic energy and potential energy) and the thermodynamics of the reciprocal conversation and heat conversation.

(**) In fact there is  not renewable energy (the first law or law of energy conservation says that whatever happens, the energy of the Universe is constant), we can not create or destroy energy, but only change one form of energy in another.  What is renewable are the processes of energy transformation, such as , for instance (i) sunlight (at least another four billion years) but photovoltaic panels are not, and  (ii) wind, however, it must be notice that gearbox of a two-megawatt wind turbine contains about 800 pounds of neodymium and 130 pounds of dysprosium  that are rare earth metals  found in scattered deposits, rather than in concentrated ores, and difficult to extract (https://thebulletin.org/2011/11/the-myth-of-renewable-energy/).

Isocotidal..............................................................................................................................................................................................................................................Isocotidale

Isocotidal / Isocotidal / Isocotidale / 同一高度潮 / Равноприливный / Isocotidal /

Line joining points with equal tide height value. This term is considered as incorrect by several geoscientists.

Ver: «Tide »
&
« Neap Tide »,
&
« Conjunction (astronomy) »

This map from Airy shows the Earth's current isocotidal lines*, that is, the amplitude of the tides. In this map, no recent revision of the daily cotidal lines was made from the huge amount of recent tide data, which have been accumulated for some years. This map prepared by Sir George Airy is a copy of the map he presented in his article on "Tides and Waves." Parts of the world for which data is not very valid have been omitted. On the other hand, the Roman numerals in the cotidal lines denote the time (in Greenwich time) of the high-tide on the day of the new or full moon. The author pointed out that the isocotidal lines of the North Atlantic are precisely drawn, while the lines of the South Atlantic are dubious, and that the East Pacific and New Zealand are, practically, conjectural. The incorporation of recent observations into the cotidal maps would, certainly, require some modification of these observations. The conjecture that when a wave oscillates in shallow water it travels with less speed and therefore its height increases, it is corroborated by the inflexion and equidistance of the cotidal lines near continents and islands of the ocean, as for example in the Azores, Bermuda and especially on the east and west coast of South America. The tidal wave propagation speed gives good information about the depth of the sea. In the North Sea, the propagation speed seems to be about 45 kilometers per hour, which corresponds to a depth of about 42 meters. On the other hand, it is well known that the depth along a deep channel is greater and that along the sides, it is smaller than 42 meters. In the Atlantic Ocean, the wave passes from 90° latitude, from the south to a north hour, in 12 hours, or at a speed of 830 kilometers per hour. If the Atlantic tide is derived, as a free wave, from the Pacific tide, the propagation velocity should correspond to a depth of 5480 meters. Airy considers that the Atlantic is a basin so large that it does not allow not take into account for direct tidal action and thinks that the tides of the Atlantic Ocean derive very little from the tides of the Pacific Ocean.

(*) For several geoscientist a cotidal line, is a line on a map passing through places having high tides at same time.

Isochrone.....................................................................................................................................................................................................................................Isochrone

Isócrona / Isócrona / Isochron / 等时线 / Изохрон / Isocrone /

Line that in a geological or seismic map indicates the same time. In a seismic map, such as the top Cretaceous map, a 2.1 second isochrone indicates that the position of the mapped horizon is 2.1 seconds deep (two way time).

See: « Geological Time »
&
« Geological Map »
&
« Seismic Line »

This maps illustrates a double-time structural map of a seismic horizon in Vietnam offshore, in which the Isochrone values were omitted for reasons of confidentiality. The isochrones allow, easily, to identify zones with smaller values, that is, less deep (underlined by +). These areas underline bell-shaped antiforms (as an anticline), but are induced by an extensional and not by compressional tectonic regime, as it is the case of an anticline (in this offshore, anticline structures occur, locally, in association with a reactivation of old normal faults in reverse faults). A geoscientist can use different contour maps: (i) Total Drilled Thickness Map Map, which shows the vertical thickness of a stratigraphic unit traversed by a vertical exploration well ; (ii) Stratigraphic Thickness Map, which shows the thickness of a stratigraphic unit measured perpendicular to the surfaces that limit it (the stratigraphic thickness is equal to the drilled thickness multiplied by the cosine of the dip of the drilled stratigraphic unit) ; (iii) Isopach Map, which shows the variations of stratigraphic thickness of a formation or geological interval using the isopachs (imaginary lines connecting points with the same stratigraphic thickness) drawn through the points where the formation has the same thickness ; (iv) Drilled Thickness Map, showing the drilled thickness variations, regardless of the true stratigraphic thickness ; (v) Isolith Map*, which is a map constructed from the imaginary lines, which connect the points with similar lithology and that separate the rocks of different nature (colours, textures, etc.) ; (vi) Facies Map, which shows the lithological variations within a stratigraphic unit ; (vii) Sub-crop Map, showing paleogeography under an unconformity, generally, tectonically enhanced (angular unconformity) ; (viii) Isochronous Map, showing the changes in depth (double time) of a given horizon (an isochrone is an imaginary line connecting points with the same reflection time).

(*) An Isolith Map is a map that contains contour lines which depict the thickness of a lithology. In an isolith map the points of a similar lithology are usually connected by a series of contours. These maps help geologists to select a particular component of the rock in a stratigraphic unit and analyzed its structure, components, thickness, permeability and other physical or chemical properties. (https://www.petropedia.com/definition/7018/isolith-map).

Isogonal (Isogonic line)............................................................................................................................................................................................................Isogonique

Isogónica / Isogónica / Isogonischlinie / 等偏线 / Изогона / Linea Isogonica /

Line that joins points with the same value of the magnetic declination angle.

See: « Contour Map »
&
« Magnetics »
&
« Magnetostratigraphy »

In the study of terrestrial magnetism (geomagnetism), an isogonic line is a line drawn across all points of the Earth's surface with the same magnetic declination. Do not confuse magnetic declination with the magnetic meridian. The magnetic declination is the angle, in a given place, between the geographical meridian and the magnetic meridian, that is, the angle between true north and magnetic north. The magnetic meridian is the great circle of the Earth passing through the north and south magnetic pole. It may be said that isogonic lines are lines of equal magnetic declination, while line agonic lines* are lines where there is no variation of magnetic declination. A magnetic compass, naturally, points to the magnetic north pole, which has nothing to do with the geographical north that is defined as the point in the northern hemisphere where the axis of rotation of the Earth intersects the Earth's surface. In the isogonics map shown in this figure, the geographic north is at the top and the isogonic lines are drawn by continuous grey lines. An airplane, which has to land at an airport located at a point where the variation between the magnetic and geographic north is 15° E, and which fly in reference to a magnetic compass / DG, the pilot has to take into account with this variation when determining the flight plan (in addition to other small variations). If the variation between the magnetic and geographic north, is Eastern, the pilot will have to subtract it. If the variation is West, the pilot will have to add it unless the pilot's compass is very recent (less than 5 years) with a compensation mechanism that automatically makes these adjustments. As we all learn in basic or geographic surveys, Earth functions like a giant magnet, like two poles. One pointing north and one pointing south. Since the compass needle is magnetized, its direction is controlled by magnetic forces on the Earth's surface and will look for the magnetic north pole. However, as stated before, the axis of the Earth's magnetic field does not exactly coincide with the axis of rotation of the Earth on the north and south poles (the magnetic north pole is currently in the Arctic archipelago of Canada).

(*) Agonic line an imaginary line on the Earth's surface connecting the north and south magnetic poles and passing through those points where there is no magnetic declination and where a freely suspended magnetic needle indicates true north (https://www.merriam-webster.com/dictionary/agonic%20line).

Isohaline..........................................................................................................................................................................................................................................Isohaline

Isohalina / Isohalina / Isohaline / 等盐度线 / Изогалина / Isoaline /

Line that joins points with equal salinity value.

See: « Contour Map »
&
« Salinity Current »
&
« Density Current »

These two isohialine maps made in August 1987 at the mouth of the Rio de La Plata (Argentina), clearly, show that salinity at sea level is smaller than at the bottom of the sea. Isohaline lines, expressed in "pus" ("Practical Unity Salinity"), that is, in grams of salt per 100 grams of water, are more distal in the sea floor than at sea level. This situation suggests that the flow of the Rio de La Plata is a hypopycnal flow, that is to say, the water flow of the river is less dense than that water-body into which it enters (South Atlantic Ocean). The water of the river, whose flow is that of an axial jet, entering the ocean, the sediments which it transports, disperse at the sea surface. Later, little by little, the sediments deposit in the bottom of the sea forming hemi-pelagites (deep-water deposit in which more than 25% of the particle fraction has a size greater than 5 micrometers). Under these conditions, highstand turbidite deposits are unlikely to be deposited on the sea floor near the river mouth (Mutti model). If a relative sea level fall puts the shoreline lower than the basin edge, i.e., if current highstand conditions change to lowstand geological conditions, the continental shelf will be exhumed and the provisional equilibrium profile of the Rio de la Plata will be broken. Therefore, the river mouth will be made at the top of the continental slope and the sedimentary particles carried by the river will be transported downstream by turbidity currents. As long as these currents reach the lower break of the continental slope (limit between the continental slope and the abyssal plain), the velocity of the currents will decrease, as well as, its carrying capacity. Such a decrease in the velocity of the currents induces the deposition of the transported sedimentary particles in the form of submarine slope and basin floor fans. The submarine slope fans will have a, more or less, wavy geometry (overbank deposits, natural marginal dikes, i.e., levees, and late fills of the depressions and turbiditic "channels"), while the submarine basin floor fans have a, more or less, horizontal geometry.

Isohyet........................................................................................................................................................................................................................................................Isohiète

Isoieta / Isohieta / Isohyete / 等雨量线 / Изогиета / Isoieta /

Line joining points with the same atmospheric precipitation.

See: « Contour Map »
&
« Map Projection »
&
« Weather (atmosphere state) »

This map in isohyets (millimeters of rain per year) from northern Borneo (Sabah) indicates the region's rainfall. it is interesting to note that the areas of lower rainfall are the coastal zones and the zones of higher altitude. This type of maps is important for locating areas of heavy rainfall and areas where river floods are most likely, what allows to predict the most likely occurrence of highstand turbidic deposits. There are two types of deep-water turbidite deposits. The first type (P. Vail model) occurs under lowstand geological conditions (sea level lower than the basin edge that may or may not to coincide with the continental edge), after a significant relative sea level fall. A significant relative sea level fall exhumes the continental shelf, as the river mouths move to the upper part of the continental slope, which causes a rupture of the provisional equilibrium profiles of the water-courses and, mainly, of great rivers. Such a rupture will force the rivers to incise their beds, to re-establish a new provisional equilibrium profile (the theoretical equilibrium profile is never reached), which, significantly, increases the terrigeneous influx, which is discharged at the mouth, i.e., on the continental slope. With the sedimentary particles carried to the water-courses mouth can not be deposited on the slope, they are transported toward the deep parts of the basin, by turbidity currents, where they are deposited either in the form of submarine basin floor fans or submarine slope fans. The second type of turbidite deposits (E. Mutti model) occurs in highstand geological conditions, i.e., with the sea level higher than the basin edge, which happens when the basin has a significant shelf. In these conditions, in areas with heavy rainfall, which can be suggested by isohyets maps, and with an appropriate topography (important mountainous and a little extensive alluvial plain, that is, with bayline near the coastline), floods and very frequent carries too much sediment to the coastline, which are transported by turbide currents to the deeper parts of the basin where they will be deposited as turbidite fans.

Isohypse (Contour line)......................................................................................................................................................................Courbe de niveau (Isohypse)

Curva de nível / Isohipsa, Curva de nivel / Isohypse, Höenlinie / 曲线水平 / Изогипса / Curva di livello /

Curve that joins points with equal altitude value.

See: « Contour Map »
&
« Orogenesis »
&
« Physiographic (province) »

A map in isohypses, like the map illustrated in this figure, is nothing more than a topographic map, that is to say, a type of map characterized by large-scale details and a quantitative representation of the relief, that, generally, uses isohypses or curves of contour lines in cartography, although in the past, a variety of methods of representation have been used. In fact, as is easy to see in this figure, when more important is the relief plus the contour lines are close to each other. On a cliff with a slope close to the vertical, like the flanks of the volcano illustrated in this figure, the isohypses are very close to each other and overlap if the escarpment is vertical. On the contrary, the greater the distance between the contour lines more flattened is the topography, which means that a horizontal area is limited upstream and downstream by the same isohypse. Conventional topographic maps not only show contours, but also any type of water-courses or other water-bodies, forest cover, builtup areas or individual buildings (function of the scale), and other features and points of interest. Currently, maps in isohypses have multiple uses, as, for instance, in urbanization, architecture, earth sciences, etc. All geological maps have a topographic base in contour lines. Geological maps are not like other maps. Geological maps, like all maps, are made to show where things are. While isohypses maps show the topography, the distribution of the roads or rivers or the county boundaries, a geological map shows the distribution of the geological resources, including the different types of rocks and faults. In geological maps, geology is represented by special colours, lines and symbols. A good geological map reading allows geoscientists to better understand the geology illustrated on the map. If the boundaries of a geological formation (a colour) cross the valley of a river or other water-course without being "apparently" diverted by topography, this means that the layers constituting the geological formation are vertical. If the limits of the formation are parallel to the isohypses the layers are horizontal or sub-horizontal.

Isolated Platform.......................................................................................................................................................................Plate-forme isolée

Plataforma isolada / Plataforma aislada / Isolierte Plattform / 隔离台地 / Изолированная платформа / Piattaforma isolata /

Carbonated platform, usually, subcircular and disconnected from the mainland by a water-body, more or less, deep.

See: « Carbonate Platform »
&
« Continental Platform »
&
« Drowned Shelf »

When a geoscientist talks about a platform, in general, he is referring to the continental shelf, which is the sloping surface of the sea-floor, bounded by a water-depth from 0 to 200 m, which is, sometimes, not the case of a carbonate platform. Thus, to avoid misunderstandings, it is important to know if the term platform is being applied to a sedimentary context where the clastics are predominant or to a carbonated context. Theoretically, under normal geological conditions, the depth-water of a limestone platform can not exceed the depth of the photic zone. Without sunlight energy can not have in situ formation of carbonate. Photosynthesis is a physical-chemistry process, at the cellular level, performed by living beings with chlorophyll, using carbon dioxide and water, to obtain glucose through the energy of the Sun, according to the following equation: Sunlight + 12H₂O (water) + 6CO₂ (carbon dioxide) → 6O₂ (oxygen) + 6H₂O (water + C₆H₁₂O₆ (glucose) Some geoscientists consider five large families of carbonate platforms: (i) Rimmed Platforms ; (ii) Carbonated Ramp Platforms ; (iii) Epeirial (or epíric) Platforms ; (iv) Isolated Platforms ; (v) Dead or Drowned Platforms. Rimmed platforms are characterized by the presence of calcareous reefs or sandstones (carbonated sandbanks covered by shallow sea water) at the edge of the platform and clay sands in the lagoon or open platform. This type of platform forms in calm waters and its range varies between 10 and 100 km. In carbonated ramp platforms, the carbonated sands of the shoreline pass at the base of the ramp to clay sands and deep water muds. In this type of platform the reefs are rare and the width of the ramp can reach 100 km. Epeirial (or epíric) platforms are characterized by the presence of tidal surfaces and protected lagoons. The width of an epeiric platform can reach 10,000 km. Isolated platforms, in which the facies (lithologies) are very controlled by the orientation of the dominant winds. These platforms have reefs and sandy bodies, such as the rimmed platform, in the windward margin (facing the side where the wind blows), but in the leeward margin (in the direction where the wind blows), the sediments are more muddy. An isolated platform can reach 100 km wide. Dead or Drowned Platforms are below the photic zone (where there is not enough light for photosynthesis, i.e., use of carbon dioxide, CO₂, and water to obtain glucose through the energy of sunlight). The most well known carbonate platform geometry is associated with tropical manufacturing processes, where carbonate platforms can be sub-divided into three main sedimentary environments: A) Reef, which is the part of the carbonate platform created in situ by sessile organisms ; B) Internal Lagoon, i.e., part of the platform behind the reef, which is characterized by shallow and calm waters with sediments composed of reef fragments and hard parts of organisms or terrigeneous sedimentary particles when the reef is epicontinental and C) Slope or Reef Slope, which connects the reef to the basin and acts as a sink for the excess carbonate sediment, although most of the sediment produced in the lagoon and reef is transported by various processes and accumulated on the slope. The example shown here corresponds to an isolated platform. On the tentative geological interpretation of a Canvas auto-trace of a detail of a seismic line, the reefs are better developed in the windward margin, which in this case corresponds to the margin facing the sea. Reefs on the proximal (continental) side are not only less developed but also more muddy. The upper part of the isolated platform corresponds to a dead platform, following a significant relative sea level rise that placed it below the photic zone, where the processes of carbonate formation are, practically, impossible. Some geoscientists subdivide the carbonate platforms connected to the continent in: (A) Flat-Topped Platform and (B) Ramp-Type Platforms. On flat-topped platforms (A) there are o two subtypes: (A.1) Rimmed and (A.2) Nonrimmed. In ramp-type platforms (B) two sub-types can be considered: (B.1) Distally Steepened and (B.2) Homoclinal. The ramp-type platforms which are frequent in cold climates, the flat-topped platforms form preferably in tropical climates.

Isopach.................................................................................................................................................................................................................................................Isopaque

Isópaca / Isópaca / Isopache / 等厚 / Изопахита / Isopaca /

Line that joins points with equal thickness value, which can be in meters or in time. In the oil industry, isopach maps (in meters) are common when made with field data or from the well results, while those made in time are drawn from seismic data.

See: « Contour Map »
&
« Orogenesis »
&
« Physiographic (province) »

The isopach map (meters) shown in this figure represents the Cenomanian-Turonian chalk thickness of the ParisGeographic Basin made from the well results drilled in this basin (each well is underlined by a small circle). As can be seen, the thickness of this formation is greater in the central part than in the edges, which is normal in almost all the sedimentary basins, since the subsidence increases towards the central part of the basin. However, the case here is somewhat different. The term "Paris Basin" is, for many geoscientists, an abuse of language. Indeed, many geoscientists consider that the so-called "Paris basin" does not correspond to a depocenter, i.e., a sedimentary basin, but rather to a vertical succession of platform deposits that later were lifted to the East and West, which gives to the whole a, more or less, circular geometry similar to that of a basin. In this geological section, practically, no interval thickens, in a significant way, to the zone of greater burial. Indeed, this map in isopachs does not translate to the subsidence responsible for the creation of most of the available space for sediments (accommodation), but more likely it underlines the erosion that the sedimentary interval has undergone. In continuity of sedimentation, i.e., in the absence of significant relative sea level falls, which create important unconformities (erosional surfaces), an isopach map, in meters, of a given sedimentary interval, emphasizes the depositional environments, where the thickest part, generally, corresponds to the continental slope and to the development of the basin edge (boundary between the continental slope and the platform or the alluvial plain, when the basin has a platform). When a map is in time, it is important to make a depth conversion before advancing any kind of conjecture or geological hypothesis.

Isopycnic...........................................................................................................................................................................................................................................Isopycne

Isopicna / Isopicna / Isopycknischlinie / 等密度 / Изопикна / Isopicnica /

Line that joins points with equal density value.

See: « Contour Map »
&
« Density Current »
&
« Atmosphere »

This map in isopycnics of wind energy over the ocean suggests that the strong densities are located at high latitudes and near the equator, which underlines the Hadley, Ferrel cells as well as the polar cells. An Hadley cell is a closed-circulation model of the terrestrial atmosphere prevalent in equatorial and tropical latitudes. This circulation is, intimately, related to the trade winds, the humid tropics, subtropical deserts and jet streams. Hadley's circulation is caused by the transport of heat from the equatorial zones to the middle latitudes, where the amount of incident solar radiation is usually much smaller. The Hadley cells extend from the Equator to latitudes of approximately 30° in both hemispheres, which is, indirectly, quite visible in this isopycnal map. This heat is transported in a cellular motion, with the air ascending, by convection, in the equatorial regions and moving to the upper latitudes, by the higher atmospheric layers. The rise of hot air in equator is accompanied by the frequent formation of convective storms in the so-called Intertropical Convergence Zone. Ferrel's cells are circulation cells that are created at the Earth's mean latitudes or any other rotating planet to balance the transport performed by the Hadley and polar cells. The movement of air in a Ferrel's cell is opposite to the Earth’s rotation. The Ferrel and Hadley cells are found in the subtropical latitudes between 30° and 35° degrees north and south, a region which is under a high pressure ridge called the high sub-tropical (horse latitudes), which is characterized by a weak rainfall and variable winds mixed with periods of calm. Polar cells are atmospheric circulations that form in the region of the poles. The dense cold air descends from the poles, which creates a high pressure. This subsidence of the air in the vicinity of the poles produces a surface current towards the equator, which is diverted, forming the eastern polar winds, in both hemispheres. Cold air moves along the surface to lower latitudes. Around 60° degrees north and south, the air was heated and rises up, creating a low pressure zone.

Isoseismal (Isoseist)..........................................................................................................................................................................................................Isoséiste

Isosista / Isossista / Isoseiste / 等震 / Изосейста / Isoseismal /

Line that joins points with equal seismic intensity value.

See: « Contour Map »
&
« Seismic Wave »
&
« Mohorovičić's Discontinuity  »

In the illustrated region, which was shaken by an earthquake, questionnaires were made to the population. The results of the analysis of the questionnaires were projected in a map taking into account the intensity of the shock according to the international scale. Then, lines were drawn which join points of equal seismic intensity, which are called isoseists. The epicentre is located in the centre of the isoseists with greater intensity. The intensity of an earthquake can be conditioned by several factors, such as: (i) The amount of energy released in the focus ; (ii) The depth to which the focus is located and (iii) The nature of the sub-soil, i.e., how the soil responds to the propagation of seismic waves. The type of rocks can condition the velocity of waves or even cause them to deviate. The intensity of earthquakes is a parameter that takes into account the effects produced by the earthquake on people, objects and structures. There are two types of scales: (A) Scale of intensities or Mercalli modified and (B) Scale of magnitudes or Richter scale. In the modified Mercalli scale twelve degrees are considered: (I) Imperceptible, when the earthquake is not felt and is only recorded by the seismographs ; (II) Very weak, when it is felt by a very few people at rest, especially by those who dwell on high floors ; (III) Weak, when felt by a small number of people, but well felt on high floors ; (IV) Moderate when it is felt inside the dwellings, being able to awaken from sleep a small number of people and with vibration of doors and windows and of the dishes inside the cabinets ; (V) Strong, when it is practically felt by the whole population, causing many people to wake up, with some less stable objects falling and opening of small crevices in the plaster of the walls ; (VI) Quite Strong, when it causes panic in the populations and produces slight damages in the dwellings, falling some chimneys ; (VII) Very Strong, when many chimneys fall with limited damage in buildings of good construction and, easily, perceivable by the drivers of motor vehicles in transit ; (VIII) Ruinous, when it causes sharp damages in solid constructions ; (IX) Disastrous, when it causes a collapse of some buildings ; (X) Destroyer, when cracks are opened in the ground; (XI) Catastrophic;and (XII) Cataclysm, when it causes total destruction.

Isostasy (Principle).................................................................................................................................................................................................................Isostasie

Isostasia / Isostasia / Isostasie / 地壳均衡 / Изостазия / Isostasia /

State of gravitational equilibrium between the lithosphere and asthenosphere so that the lithospheric plates "float" with a certain elevation, which depends on their thickness and density. Isostasy is invoked to explain the differences in topographic height at the Earth's surface. When an area of the lithosphere reaches the state of isostasy it is said that it is in isostatic equilibrium (like an iceberg). Isostasy is the hypothesis that admits that the Earth's crust floats in a very viscous liquid and that it responds according to the charge.

See: « Glacio-Eustasy »
&
« Subsidence »
&
« Unloading »

The principles of isostasy are illustrated in this figure: (i) Two blocks A and B, of density D_y and D_x, float in a liquid of density D_f ; (ii) The pressure at points A', B' and PC' must be the same (pressure at the compensation depth); (iii) Thus: X₂ x D_f = (Y₂ + Y₁) x D_y + Y₃ x Df = (X₁ + X₂) x D_x ; (iv) Knowing the density of the fluid (Df) and the values of X₁ and X₂ or of Y₂ + Y, the density of the blocks can be determined. Since the charge decreases, one of the consequences of isostasy is the isostatic rebound or isostatic uplift (also known as a crustal rebound). In areas that have been covered by Quaternary ice caps, such as northern Europe and Canada, the cliffs of beaches and dunes are, currently, about 300 meters above sea level. For an ice thickness of 2,000 meters, similar to the one that exists today in Greenland, the terrain sinks about 700 m. The ice density is about one third of the density of the mantle. The ¹⁴C dating of the sea shells and plant remains indicate that the isostatic uplift postdate the glaciations (less than 14,000 years), which means that the cliffs and dunes formed at sea level and that despite the sea level rise (glacio-eustasy), they were further raised by isostasy. In the areas where the uplift was well dated by ¹⁴C, it was done with an exponential decreasing rate. Half the recovery time is several thousand years. Thus, northern Europe and Canada continue to regain their original position, albeit much more slowly than initially, that is, at the beginning of deglaciation. In these areas, the old port facilities (hundreds of years ago), such as those of the Vikings and Greeks are today several kilometers landward of the coastline above sea level. The isostatic uplift, provoked by the melting of the ice sheets, is very visible in the seismic lines of the North Sea, as illustrated by the Canvas auto-traces in this figure. In fact, a few kilometers from the coastline, the sediments deposited, initially, more or less, sub-horizontally, as the submarine basin floor fans were raised (lengthened and tilted) once the continent has suffered and still suffers an isostatic rebound. The uplift of the sediments increases toward the mainland. The same is true for the continental slope sediments which, following the isostatic uplift, exhibit a seaward dip far higher that the dip permitted by the critical angle of stability. This isostatic uplift is well known in Norway's topographic and tax services, as the area of coastal farms increases regularly (the first measures date back to the fifteenth century), once the shoreline moves seaward (relative sea level fall). In conclusion, isostasy is the geological translation of the hydrostatic impulses described by Archimedes principle: "A body totally or partially submerged in a resting fluid receives a pulse from the bottom up. which equals the volume equal to the weight of the fluid it moves. " This force called Archimedes' impulse or hydraulic impulses, is measured in Newtons, and is calculated by the following formula: E = Pe V = ρf g V or when determined to compare it with the weight of the object: E = Pe V = ρf g V, where "E" is the pressure [N], "Pe" is the specific gravity of the fluid of [N / m³]², "Rf" is the density of the fluid, "V" is the volume of fluid displaced by a body immersed partially or completely therein, "g" acceleration of mass mass m. Thus the impulse depends on the density of the fluid, volume of the body and gravity therein. The impulse (in the simplest described conditions) acts vertically upward and is applied in the centre of gravity. This point is called the impulse centre. In order to get equilibrium in a lithospheric plate, if there is an increase in weight (existence of topographic elevations or the presence of sediments or masses of ice or water), it implies a corresponding sinking of the plate, and vice versa. However, this process takes place on a geological time scale and is subject to the homoeostasis* resulting from the complexity of the geological system. The lateral flows necessary to adjust for variations are very slowly occurring: Scandinavia continues to rise slowly (about 9 mm/yr) by isostatic adjustment as a result of the disappearance of the ice of the last glaciation, and will continue for many hundreds of thousands of years.

(*) Property of an open system, especially of living things, to regulate its internal environment, in order to maintain a stable condition through multiple adjustments of dynamic equilibrium, controlled by interrelated regulatory mechanisms.

Isostatic Change in Sea Level...................................Changement isostatique du niveau de la mer

Mudança isostática do nível do mar / Cambio isostático del nivel del mar / Isostatische Veränderung des Meeresspiegels / 地壳均衡的海平面变化 / Изостатическое изменение уровня моря / Variazioni isostatica del livello de mare /

Change of the absolute or eustatic sea level due to a charge removal on the Earth's crust. The isostatic movement refers to the gravitational equilibrium state between the lithosphere and the asthenosphere, resulting from the fluctuation of the lithospheric plates on the denser material of the asthenosphere, whose equilibrium depends on its relative densities and the weight of the plate. Such equilibrium implies that an increase in the weight of the plate (by thickening or deposition of sediments, water or ice on its surface) leads to its sinking, a rise (often called isostatic) occurring inversely when the weight decreases.

See : « Isostasy (principle) »
&
« Glacio-Eustasy »
&
« Isostatic Rebound »

The Earth's mantle is still flowing laterally to fill the areas beneath the places where the thick, heavy layers of ice that forced the mantle to sink about 20,000 years ago, at the maximum of the last glaciation. In this photograph of the West Coast of New Zealand, relative sea level changes, during the isostatic uplift (rebound), can be reconstructed from the successively uplifted beaches, which, in reality, correspond to fossil shorelines. Similarly, in northern Europe, isostatic uplift is, easily, recognized not only in Greenland but also on the Norway coast, where the surface of almost all rural coastal properties has increased, since the first official cadastral census made in the 16th century. It was the American geoscientist Clarence Edward Dutton of the United States Geological Survey who first suggested that changes in shorelines could be the result of adjustments of continental materials, if the volume of water in all its forms is constant since the Earth's formation. At present, all geoscientists know that, on the Earth, starting from a certain depth (between 50 and 100 km), the temperature is sufficient for the sub-lithospheric mantle have a plastic behaviour in relation to the more rigid material of the overlying lithosphere (continental crust, oceanic crust and lithosphere mantle). In fact, the lithosphere seems to float over the asthenosphere. This means that when, for any reason, there is a change in the morphology of the upper limit of the lithosphere, at the level of the asthenosphere there is compensation by isostatic uplift or sinking, in order to compensate such a morphological alteration. The isostatic uplift is, perfectly, corroborated by all seismic lines shot in Norway offshore. Near the shoreline all seismic lines show a clear truncation of the pre-melting horizons, which, of course, have important implications for the assessment of the oil potential of certain regions, such as the North Cape geographic basin (Nordkapp) and in the Svalbard archipelago (Bears island). Today, in this region all the sedimentary intervals rich in organic matter, that is to say, all the potential source-rocks are, insufficiently, buried. The organic matter of the potential source-rocks, likely, has not reached the catagenesis zone, where it can generate oil or gas. However, taking into account the isostatic uplift, which can reach several hundred meters (even a couple of thousand meters), certain sedimentary intervals have been buried, sufficiently, so that the organic matter of its potential source-rocks would reach maturation (oil window). The isostatic uplift is partially, compensated by the rise of the absolute (eustatic) sea level (supposed global sea level, referenced to the Earth's centre or to a satellite) produced by the melting of the ice caps and glaciers. On the other hand, it may increase slightly, mainly due to the melting of the ice shelves and pack ice (formed on the surface of the sea, by solidification of the first layers of water) and the "pack*", since the ice is less dense than the water. Thus, when determining the isostatic uplift, do not forget to take into account the absolute sea level rise caused by deglaciations. Certain geoscientists estimate that absolute sea level has risen about 120 meters since the last glacial period, which means that a raised beach that is now 50 meters high, in fact, has been raised at least 170 meters. The East of Scotland, which at the peak of the last glaciation, was covered by a layer of ice (more or less, 1 km thick) has risen between 40 and 50 meters in the last 1,000 years. This isostatic rebound is still ongoing, averaging 0.2 cm per year. If the isostatic uplift continues in Britain, it will greatly increase the slope of the terrain. Northwest of Scotland has risen about 10 m in the last 9,000 years, while the SE of England has sunk, in such a way that the tides in London have, presently, 4 m more of amplitude than 4 m the time of the Romans. At present, in several places, the isostatic uplift due to the decrease in the weight of the ice created raised beaches and caused the rejuvenation of the many watercourses

(*) Mass of floating ice of salt water, unlike the icebergs, that have stood out of the ice pack and that may or may not be welded between them.

Isostatic Rebound................................................................................................................................................Soulèvement isostatique

Levantamento isostático / Levantamiento isostático / Isostatischen Rebound / 等静压反弹 / Изостатическое поднятие / Sollevamento isostatico /

Elevation of the continent in response to the discharge induced by the removal (melting) of the ice from the ice caps. Synonym with Isostatic Rebound.

See: « Glacio-Eustasy »
&
« Isostasy (principle) »
&
« Relative Sea Level Change »

On this tentative geological interpretation of a Canvas auto-trace of a seismic line from the West Norway offshore , the isostatic uplift (rebound or readjustment) induced by the discharge (melting) of the glacial ice, that covered the North Europe and, particularly, Norway during the beginning of the Quaternary, is perfectly visible. At the top of this tentative interpretation, reflector terminations underline a tectonically enhanced unconformity (angular unconformity), which emphasizes the relative sea level fall* that occurred during the Middle Miocene. As can be seen, the eastern part of this unconformity was raised several hundred meters. This local uplift, which is confirmed by the thickness variation of the Quaternary sediments after the melting of the ice, was induced by the isostatic rebound, which accompanied the melting of the ice of the Quaternary glaciations. In fact, during the last glacial period, most of northern Europe, Asia, North America, Greenland and Antarctica were covered with ice sheets and ice caps**, as well as by ice seas. The thickness of the ice reached about 3,000 meters at the Last Glacial Maximum ***(LGM), about 21,000 years ago (calibrated age) or 19,000 B.C. The enormous weight of this layer of ice forced the crust to deform in an inverted bell shape (sinform, extensional structure, the rocks are lengthened), which forced the material of the terrestrial mantle to flow away from the overloaded area. Since the temperature had increased and the ice began to melt, the removal of the overload from the sunken region caused an uplift of the area and a return of the material from the Earth's mantle to its original position, that is, to that which it had before glaciation. Taking into account, the viscosity of the mantle material, it will probably take several thousand years for the Earth's surface to reach an isostatic equilibrium. For an ice thickness of about 2,000 m (as there is today in Greenland), the terrain sank about 700 meters (the ice density is about 1/3 of the density of the mantle). All this has a very great influence on the variations of the absolute (eustatic sea level), which, during the glaciations, fall and later rise during thawing. The Norway isostatic uplift is well known from the cadastral survey. In fact, since these services exist in Norway, they have found that the area of farms near the coast, regularly, increase due to the isostatic uplift. The importance of the glacio-isostatic movements associated with the last glaciation in the modelling of the coastline of Europe and North America is immense. In the European coast, the fjords of Norway, the Baltic Sea and North Sea, as well as the separation of Britain and Ireland from the continent, are the result of glacio-isostasy. Central Scandinavia continues to rise at the rate of 9 mm/year. in the American side, the Great Lakes, Hudson Bay and morphology of Canada's Arctic coast are the direct result of the sinking and uplift of the crust in that vast region. On the other hand, old coast lines and raised beaches are quit well visible. This phenomenon, which theoretically corresponds to an absolute sea level fall, is observed in several parts of the world, as in New Zealand, where the old coastlines and raised beaches are well known of the geoscientists. Another indirect relation that contributes to the complexity of the absolute sea level is the thermal expansion of sea water when the average Earth's temperature increases, which is in addition to the variations induced by the vertical movements of the crust, changes in the rate of Earth's rotation, large-scale changes in continental margins and changes in the sea floor spreading rate. Absolute sea level rise from tide gauge records and satellite altimetry, presently advanced by IPCC, that several geoscientists contest, are around +3 mm / y (2007 data, IPCC).

(*) Local sea level, referenced to any point on the Earth's surface but, generally, to the base of the sediments (top of the continental curt) or to the sea floor, which is the result of the absolute (eustatic) sea level and tectonics (subsidence or uplift of the sea floor). The absolute sea level, which is the supposed to be global, is referenced to the Earth's centre (presently, NOAA, i.e., the National Oceanic and Atmospheric Administration, uses satellite altimetry that must be calibrated by corrected tide-gauge results, that is to say, taking into account the subsiding and uplifting site areas).

(**) A glacial ice cap is a mass of ice that covers less than 50,000 km² of the Earth's surface (usually covering a mountainous region). A mass of ice covering more than 50,000 km² is an ice sheet. Unlike a ice sea (floating ice that when it melts contributes to a fall the sea level, since the ice is less denser than the water) the melting, totally or partially, of a glacial ice cap induces a rise of the level from the sea. The Antarctica ice cap ( inlandsis), which began to melt some 19,000 B.C, has, certainly, contributed significantly to the rise of the absolute sea level during the Holocene (the present-time edge of this ice cap is, around, 450 km south from the initial edge).

(***) Around 130 ky, the end Riss glacial cycle is marked by a rise of temperatures and a rapid melting of Arctic ice caps. This melting leads to a rise in sea level of about 120 meters. Warming is maximum around 120 ky. Then, a cooling takes place. It was the starting of Würm glacial cycle. During this last glacial cycle (Würm), which last around 100 Ky, five stage of cooling (20 ky each). The last glacial maximum (LGM) was around 21 ky., i.e., just before the beginning of Holocene.

Isotachyte..................................................................................................................................................................................................................................Isotachyte

Isotáquia / Isotaquia / Isotachyte / 相同的速度 / Изотахита / Isotaquia /

Line that joins points with equal velocity value.

See: « Contour Map »
&
« Stream »
&
« Flux »

The speed of flow of a glacier is best understood by the glacier isotachyte maps. The flow of glaciers is an important process in the cold mountains and polar regions. The glaciers move downhill, showing various velocity patterns within the flow system and shape the terrain. The flow is influenced by the gravitational force, tectonic conditions, climate and climatic changes, weathering, water cycle, etc. Therefore, the surface of a glacier, like all other elements that make up it, change in space and time. The quantification and visualization of the movements of the surface of a glacier is important for the understanding and modeling of the dynamic processes involved in the ice flow, as well as to estimate the system response to the environmental conditions he changes. In isotachyte maps, in most cases, the results of the displacement measures are visualized by static vectors, which represents the amount of displacement (and speed, respectively) for each chosen point. The vectors have their starting point in place of the object located in a first picture and point in the direction of the corresponding object in a second picture taken later. The length of the vector is proportional to the calculated speed. In its simplest form, the velocity field is visualized with these vectors only, without any symbolization or complementary information. For better orientation, this view is often combined with terrain information, such as contour lines, relief shading, and/or ortho-images (image, which when displayed in digital form, represents the projected features orthogonally with a constant corrected scale of the displacement due to the relief and inclination of the chamber being thus geometrically equivalent to a map). In this way, similar measures can be taken to those that are made on a map. In addition to the vector field, the isotopes can be overlapped to support the overview of flow conditions. Visions only of isotachytes (without vectors) can be used to provide an overview of the velocity conditions on the surface of the glacier, but information on the directions of flow must be deduced. Either way, a glacier flows downhill which means that since a glacier does not flow downstream it no longer exists. The term retreat from a glacier is, in our view, a language error. A glacier can not flow updip. We prefer to say that a glacier slims and not that a glacier retreats.

Isotherm.............................................................................................................................................................................................................................Isothérmique

Isotérmica / Isotérmica / Isothermischlinie / 等温线 / Изотермический / Isoterma /

Line joining points with equal temperature value.

See: « Thermal Flux »
&
« Contour Map »
&
« Isobathytherm »

The map shown in this figure represents the average temperatures measured in the Iberian Peninsula in a month January. The year of these determinations does not matter to us much, since we have no intention to say if, at the moment, the climate is hotter or colder than before and especially if these variations are of anthropogenic origin (increase of the content of CO₂ in the atmosphere induced by the combustion of fossil energies) or not. What is interesting to note is the amplitude of the variations between the coastline temperatures, that is, plus or minus 12° C and the temperature of the high points which is plus or minus 2° Celsius, which means that the average temperature in the Iberian Peninsula ranged from 10° C. This variation is very small when compared to the variations of other regions, not to mention the daytime and night-time temperatures (in the same month and day) in Hassi Messaoud (Sahara desert). The main reason why these differences interest us is that certain geoscientists, who are an integral part of the environmental political movements (the famous watermelons, that is to say, greens outside and reds inside), tell us, after correcting (but in what way?) the average temperature differences that we are headed for a catastrophe because their models (mathematical or not) suggest a temperature rise of about 3° C (2 to 6) in the next 100 years. When I tried to explain this to my friends from Vila Real (Trás-os-Montes, Portugal), who fortunately still had not lost the common sense of their ancestors, one of them told me: "But this is a marvel, so my grandchildren will not need go to the Algarve in the winter, as I do, that's good." The determination of the average temperature of the Earth is extremely difficult to determine, even with the corrections made by specialists, since the average temperature range at the poles and the equator sometimes exceeds 70 ° C. An interesting example is the summer of 2010. Indeed, those living in Europe consider that the winter of 2009 was very cold and that the summer of 2010 was a bit warmer. However, the Portuguese media said yesterday (29 September 2010): "this summer has been the hottest summer since 50 years" taking evidently as a reference the temperatures of Australia*.

(*) As everyone knows, inaccurate or misleading claims by interesting lobbies, range from a simple lie, to a lie by omission to a lie by selection. "Lying and credulity mate and generate opinion" (Paul Valérie, "Le mensonge et la crédulité s'accouplent et engendrent l'opinion" Œuvres i, 1941, Édition Gallimard, coll. bibliotheque de la pleiade, 1957, chap. instants, p. 376 ).

Isotope.........................................................................................................................................................................................................................................................Isotope

Isótopo / Isótopo / Isotop / 同位素 / Изотоп / Isotopo /

Atom with the same number of protons, but with different number of neutrons and, thus, with an atomic mass different from another atom. As the kinematic and thermodynamic properties of the molecules are mass dependent, a partial segregation of isotopes occurs during physical and chemical processes, so that, they can be impoverished or enriched.

See: « Nucler Fusion »
&
« Radioactive Decay »
&
« Radiometric Dating »

Isotopes are atoms of a chemical element whose nuclei have the same atomic number, that is, they contain the same number of protons designated as "Z", but different numbers of atomic masses, designated "A". Isotope means "in the same place," They are in the same place in the periodic table, which is a systematic arrangement of the elements, in the form of a table, according to their properties. The difference in the atomic weights results from the difference in the number of neutrons in the nuclei, that is, the isotopes are atoms that have the same amount of protons but not the same of neutrons. As shown, the hydrogen atom has three forms of isotopes: (i) Protium (1 proton without neutron). Deuterium (1 proton and 1 neutron) and Tritium (1 proton and 2 neutrons). In scientific nomenclature, isotopes are designated by the name of the element followed by a hyphen and by the number of nucleons (protons and neutrons) in the atomic nucleus (e.g., iron-57, uranium-238, helium-3). In symbolic form, the number of nucleons is written as a prefix raised from the chemical symbol (ex: ⁵⁷Fe, ²³⁸U, ³He). There are 339 natural isotopes on Earth and over 3100 are known. A well-known example of a pair of isotopes is carbon, which is present mainly under its isotope of atomic weight 12 (carbon 12). However, small amounts of its isotope of atomic weight 14 (carbon 14), which is chemically equivalent to carbon 12, but radioactive, can be found. The supplementary neutrons in the nucleus make the atom unstable. It disintegrates giving nitrogen while it emits beta radiation. The ratio of the stable isotope to the unstable isotope is the same in the atmosphere and in the tissues of living organisms, but since an organism dies, it varies regularly with time, since the exchanges between the organism and the environment stopped. It is in this variation that the best-known dating methods for carbon 14 are based.

Send E-mails to carloscramez@gmail.com or to carlos.cramez@bluewin.ch with comments and suggestions to improve this glossary.
Copyright © 2009 CCramez, Switzerland
Last updated: August, 2019