Early Highstand...............................................................................................................................................Haut niveau précoce (de la mer)
Nível alto precoce / Nivel alto precoz (del mar) / Frühe Highstand, Früh hoch (Meer) / 早期高位 / Преждевременно высокий уровень моря / Alto livello del mare (precoce) /
Geological conditions of sea level (highstand) during which the submarine canyons and, above all, the incised valleys are filled. Also called lower high sea level. Are the sediments of the top of the lowstand prograding wedge (LPW) that are deposited during the early high sea level as well as the incised valleys and submarine canyons fills. The sediments of the base of the transgressive interval (TI), are, already, deposited during a high sea level. These are characterized by a retrogradational geometry though, between two relative sea level rises (in acceleration), the geometry of the chronostratigraphic lines is progradational. The sediments of the top of the lowstand prograding wedge have a progradational geometry.
See: « Sequence-Cycle »
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« Highstand (sea level) »
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« Relative Sea Level Change »
A stratigraphic cycle said sequence-cycle is induced by a 3rd order eustatic cycle, i.e., an eustatic cycle limited between the two consecutive significant relative sea level falls, whose age difference (time-duration of a cycle) is between 05 and 3-5 My. The morphology of the erosional surface associated with the lower discordance, which is the lower boundary of the sequence-cycle, is controlled by the last basin edge of the underlying stratigraphic cycle (last edge of the lowstand prograding wedge of the previous cycle). At the beginning of the new sequence-cycle, the sea level is lower than the basin edge and the geological conditions of the basin are said to be lowstand. It is during these geological conditions that the lowstand systems tracts group (LSTG) is deposited. It is composed by three sub-groups: (i) Submarine basin floor fans (SBFF), at the base ; (ii) Submarine slope fans (SSF), in the middle and (iii) Lowstand prograding wedge (LPW), at the top. This means during the deposition of these sub-groups, the basin edge is always, more or less, the last continental edge of the highstand prograding wedge of the previous sequence-cycle (when the underlying sequence-cycle is complete, i.e., formed by all sub-groups of the systems tracts groups, which is not always the case). Since relative sea level floods the coastal plain of the lowstand prograding wedge (LPW), which aggradates continental slope, that certain geoscientists call early highstand, the geological conditions change to a highstand geological conditions with the beginning of the deposition of the lower sub-group of the highstand systems tracts group, i.e., the transgressive interval (TI). However, other geoscientists use the term early highstand to designate the geological conditions during which the submarine canyons and, above all, the incised valleys are filled. For these geoscientists, during the early highstand, the relative sea level* is still lower than the basin edge, but locally, due to the erosion induced by the previous relative sea level fall, in certain areas (submarine canyons and incised valleys) deposition may occur. On this tentative geological interpretation of a Canvas auto-trace of a detail of a seismic line from the offshore of Labrador (Canada), lowstand systems tracts sub-groups, namely, the submarine basin floor fan (SBFF) and submarine slope fans (SSF) of the considered sequence-cycle, as well as the lower part of the lowstand prograding wedge (LPW) are not visible. They are located eastward of this line. However, since the first flooding of the coastal plain of the lowstand prograding wedge (LPW), the geological conditions change to highstand. The new basin edge is given by the last coastal plain edge of the lowstand prograding wedge (LPW). After the early highstand period, which precedes the coastal flooding, the relative sea level rise in acceleration inducing the deposition of the transgressive interval (TI). As illustrated on this tentative interpretation, the transgressive interval (TI) is characterized by a retrogradational geometry (displacement of the shoreline or of the depositional coastal break continentward). The retrogradational geometry of the transgressive interval (IT) is the result of the combination of increasingly important marine ingressions (relative sea level rising in acceleration) and associated, increasingly smaller sedimentary regressions. That means what many geoscientists called a "sedimentary transgression" is only a stacking of smaller and smaller sedimentary regressions. On the contrary, the progradational geometry of the highstand prograding wedge is the result of a set of increasingly smaller marine ingressions (relative sea level rising in deceleration) and increasingly important sedimentary regressions. Thus, at the level of a sequence-cycle it is wrong to say that "When the sea level rises (whether it is relative or absolute) there is a transgression and when it falls there is a regression". Within a sequence-cycle, to have deposition, with the exception of the submarine fans, the relative sea level must always rise, which means that the shelfal accommodation has to increase.
(*) Sea level, local, referenced to the base of the sediments (top of the continental crust) or to the sea floor. It is the result of the joint action of absolute or eustatic sea level (sea level, global, referenced to the Earth's centre), and tectonics (subsidence, when the predominant tectonic regime is extensional or uplift, when it is compressional).
Early Universe..........................................................................................................................................................................................Univers primitif
Universo primitivo / Universo primitivo / Frühen Universum / 早期宇宙 / Ранняя Вселенная / Universo primordiale /
Period of evolution of the Universe that begins at the end of cosmic inflation (about 10-16 seconds after the Big Bang) and goes until the end of the dark period (about 400 ky after the Big Bang).
See: « Big Bang (theory) »
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« Hubble's Constant »
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« Universe (age) »
At present, the Universe seems to be dominated by black energy, since about 70% total mass-energy of the Universe is dark energy. The remaining 30% encompasses all matter (dark matter and normal matter). Most of the radiation is the radiation from the cosmic background. The radiation from stars and galaxies is very weak. However, it has not always been so. The early Universe was dominated by a density of radiation that exceeded the density of matter. About 50 k years after the Big Bang, the density of matter exceeded the density of radiation, which dominated, eventually, the Universe. At present, dark energy dominates the density of matter. At the beginning of the Universe, matter and anti-matter were created in the same way from the production of radiation pairs. The production of pairs is the production of matter and anti-matter in pairs. Anti-matter is a type of matter that has the same mass as normal matter, but an opposite charge. Matter and anti-matter can be created in pairs of energy (or electromagnetic radiation), E = m c2, where E = energy, m = mass and c2 = speed of light squared. For example, energy -> proton + antiproton or energy -> electron + positron. On the contrary, matter can be annihilated in pairs, as for example: proton + antiproton ---> energy or electron + positron (anti-electron) -> energy. The basic conjectures about the early Universe are: (a) Matter, eventually, dominates antimatter (antiparticles) ; (b) At first, due to the high temperature, the matter and antimatter were created continuously and the particles and antiparticles were in equal number ; (c) Matter (which was, initially, equal to antimatter) has become dominant (experiments on high energy accelerators show that if you start with equal amounts of matter and antimatter, the interactions will produce a slight excess of matter) ; (d) The higher the radiation temperature, the greater the energy of the photons and the larger the mass of particles created in pairs; (e) Since the temperature decreases, even the slightest particles can not be created which certainly occurred about a minute after the Big Bang.
Earth........................................................................................................................................................................................................................................................................Terre
Terra / Tierra / Erde / 地球 / Земля / Terra /
The third planet in the solar system, between Venus and Mars, and the largest of the terrestrial planets (mainly formed by silicate rocks) of the solar system, by its diameter and its mass.
See: « Density Current »
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« Geoid »
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« Moon »
The Earth is the third planet from the Sun, of which it is at 149.6 Gm. Its surface is 510 065 600 km2, the diameter (at the equator) is 12,756 km and its volume d is 10 832 073 Tkm3. About 70% of the Earth's surface is covered with liquid water. The rest is divided into seven continents: (i) Asia, with 29.5% of emerging land ; (ii) Africa, with 20.5% of emerging land ; (iii) North America, with 16.5% ; (iv) South America, with 12% ; (v) Antarctica, with 9% ; (vi) Europe, with 7% and finally (vii) Australia, with 5% of the land emerging. This definition of the continents is, mainly, cultural, since, for example, any water-body separates Asia from Europe (Lucy & Stephen Hawking, 2007). On Earth, a day is divided into 24 hours, but in reality, the Earth spends 23 h 56 m 4 s to make a complete spin on itself. Over a year, all differences (3m 56s per day) are added to determine the time spent by the Earth to make a revolution around the Sun, whose period varies slightly, but, it can be said, it is about 365.25 days. To this day, Earth is the only known planet with life. From the petrographic point of view, the Earth is divided into three main layers: (1) Crust ; (2) Mantle, which can be sub-divided into Upper and Lower and (3) Core, which is, usually, sub-divided into inner core (solid) and outer core (liquid). It is the liquid core that generates the terrestrial magnetic field. A transition zone between the inner and outer core is considered by certain geoscientists. From the mechanical point of view, the Earth is divided into four layers: (a) Lithosphere ; (b) Asthenosphere; (c) Mesosphere, which can be sub-divided into Lower and Upper and (d) Siderosphere. The siderophere, corresponds to the petrographic core, but the other mechanical sub-divisions do not correlate with the petrographic divisions. The lithosphere is divided into several rigid segments called tectonic plates, which move one in relation to the other for periods of millions of years. The movement of the lithospheric plates (plate tectonics) explains not only the distribution of the continents and oceans, but also the distribution of mountains, volcanoes, earthquakes, mineral resources, life, etc.
Earth's Crust...................................................................................................................................................................................................Croûte terrestre
Crusta / Corteza continental / Kontinentale Erdkruste / 大陆地壳 / Континентальная кора / Crosta continentale /
Top of the lithosphere. The Earth's crust may be volcanic (subaerial or oceanic) or continental. Synonym of Earth Crust.
See: « Lithosphere »
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« Asthenosphere »
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« Earth »
In this diagram one should not confuse petrographic divisions (based on composition) and rheological divisions (based on behaviour, that is to say, on rheology, which is the way matter flows or deforms). The crust is a petrographic division. The crust can be continental, when the rocks that form it have a sialic composition (abundance of granitic rocks) or oceanic, when the rocks that form it have a mafic composition (abundance of basaltic rocks). The crust is separated from the mantle by the Mohorovičić discontinuity, which marks an abrupt increase in the velocity of the seismic waves. The lithosphere is a rheological division. It encompasses the uppermost part of the mantle, above the isotherm 1350° (beginning of the low-velocity zone of the seismic waves) and the crust. In the asthenosphere, which can reach a depth of about 350 km, there are slow convective movements that explain the drift of the continents (Plate Tectonics). Asthenosphere basalt flows by extrusion along the mid-ocean ridges, which renews, constantly, the ocean floor and also forces the old dense oceanic crust to plunge into the asthenosphere (subduction) along the converging edges. The mantle, which is mostly solid, has an average thickness of about 2,900 km and corresponds to about 70% of the total volume of the Earth. The mantle encompasses the core which is very rich in iron and represents the remaining 30% of the volume of the Earth, which means that the crust represents less than 1% of the volume of the Earth. The core seems to consist of iron and nickel. The core is less dense than iron. About 10% of the core should consist of any less dense material than iron. Sulphur and oxygen appear to be the most obvious candidates. However, hydrogen has also been proposed. The inner part of the core is, probably, solid, whereas the outside appears to be liquid, since the outer-core reflects the S waves and deflects the P waves (the S waves are reflected because they can not travel through the liquids and more shade than P waves deviated).
Earth's Sciences.........................................................................................................................................................................Sciences de la Terre
Ciências da Terra / Ciencias de la Tierra / Geowissenschaften / 地球科学 / Науки о Земле / Scienze della Terra /
Set of disciplines studying all aspects of the Earth and its relations with the Universe.
See: « Earth »
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« Lithostratigraphy »
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« Paleogeography »
The total content of Earth Sciences and Geosciences as, at present, they are, commonly, designated, is a matter of dispute, but no critique excluded: (i) Geology, which describes the rocky parts of the Earth's crust and its historical development (the main ones are branches of geology are Mineralogy, Geomorphology, Stratigraphy, Structural and Tectonic Geology, Sedimentology, etc.) ; (ii) Oceanography, which describes the marine and freshwater areas of the hydrosphere (the main branches are Hydrogeology, Physical Oceanography, Chemical Oceanography and Biological Oceanography) ; (iii) Atmospheric Sciences, which include Meteorology, Climatology, Atmospheric Physics and Atmospheric Chemistry) ; (iv) Geophysics that studies the shape of the Earth and its relations with magnetic and gravimetric forces and fields, as well as exploring the Earth's core/mantle and the tectonic and seismic activity of the lithosphere, and (v) Geochemistry, which deals with the study of chemical composition of the Earth, processes and chemical reactions that govern the composition of rocks and soils, and the cycles of matter and energy that carry the Earth's chemical components in time and space, and its iteration with the hydrosphere and atmosphere. Most geoscientists also include in Earth Sciences, Cosmology, Cosmogony, Astronomy and Ecology, and even Geography. As with specialization, each of these disciplines has been subdivided into different branches that are also included in earth science, such as, for example: a) Paleontology ; b) Geomorphology ; c) Mineralogy ; d) Petrology ; e) Petrography ; f) Economic Geology ; g) Volcanology ; h) Meteorology ; i) Paleoclimatology ; j) Modern Climatology ; k) Oceanography ; l) Paleoecology ; m) Stratigraphy ; n) Sequential stratigraphy, etc., as well as a wide variety of subjects related to ecology. Just as all those who study life are recognized in biology and accept to be called biologists, today most of the specialists who study Earth sciences are designated as geoscientists, which means that most of the disciplines that are part of Earth's Sciences can no longer be included in Geology.
Ebb (Falling tide)............................................................................................................................................................................Descendante (courant de maré)
Vazante (corrente de maré) / Bajante (corriente) / Flut / 落潮 / Отлив (понижение уровня воды) / Caduta di marea /
Return current from the tide once the water returns to the sea.
See : « Tide »
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« High Tide »
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« Oposition (astronomy) »
The tides are the sea level changes caused by the gravitational interference of the Moon and the Sun (the latter with less intensity due to its great distance from Earth) over the Earth's gravity field. In an ideal terrestrial gravitational field, i.e., without interference, the waters of the Earth's surface would suffer an identical acceleration towards the centre of terrestrial mass, thus being in an equipotential situation. Due to the existence of bodies with significant gravitational fields interfering with that of the Earth, such as the Moon and the Sun, they cause accelerations that act on the Earth mass with different intensities. As the gravitational fields act with an intensity inversely proportional to the square of the distance, the accelerations felt in the different points of the Earth are not the same. The acceleration caused by the Moon has, significantly, different intensities between the points closest to and farther from the Moon. In this way the oceanic masses that are closest to the Moon undergo an acceleration of intensity higher than the ocean masses further away from the Moon, which causes changes in the height of water bodies to the surface of the Earth. When the tide is at its apex it is called high tide, full tide. When sea level is at its lowest level it is called low tide. On average, the tides oscillate in a period of 12 hours and 24 minutes. Twelve hours due to Earth rotation and 24 minutes due to lunar orbit. (http://en.wikipedia.org/wiki/Maré). As normally, the rise of the tide in an estuary causes a flood (tide flood) and a descent of the tide causes a flow of ebb or ebb (ebb tide), the currents are, practically, null near the high-tide and low-tide. When this occurs, many geoscientists say that the tidal wave is in phase with the variation of the currents and the tidal wave is said to be stationary. However, this is not a rule. In long, low-converging estuaries, or in channels leading to internal lagoons, vertical tide (rise and fall) may be associated in a different way with the horizontal tide (tidal currents).
Ebb Delta.....................................................................................................................................................................................................................Delta de Jusant
Delta de Vazante / Delta de reflujo / Ebbedelta / 大浪淘沙三角洲 / Отливная дельта / Delta di riflusso /
One of the two tidal deltas. The ebb delta is the smallest and forms on the outer side (facing the sea) of the openings of the lagoons or in the tidal coves. The delta forming on the inner side is the delta of flood, which, in general, is better developed and less irregular than the ebb delta.
See: « Delta »
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« Tidal Delta »
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« Flow Delta »
In the geological model of an ebb delta, shown in this figure, we recognize; (A) Barrier-Bras or spits (coastal structures constructed by the combined action of transporting materials by large rivers and by the sea), which replace the contours of the coast and in which the beach, dunes and overbank deposits can be identified ; (B) The tidal channel, which individualizes two barriers-bars ; (C) The ebb delta ; (D) The tidal flat ; (E) The swamp and (F) A secondary tidal channel. Along the barrier-bars, which are forms of accumulation of sand and pebbles, developed in the back-shore, due to the accumulation of sediments by the waves, in association with the tides, groups of small underwater deltas can be formed, which form in symmetrical position in the inlets of the lagoons or straits. The deltas, which form on the outer side are the ebb deltas, as illustrated in this photograph. The deltas, which develop inland and are, generally, smaller in size and more irregular (due to wave ripples ) are the flow deltas. It may be said the large sandy bodies, which accumulate in the open sea at the end of a tidal cove, as shown in this figure, are ebb deltas, as opposed to the flow deltas, which form on the inner side of the on the lagoon side. The ebb delta are, in general, composed of sand and thin fragments of shells. The characteristics of the sediments make the ebb delta one of the preferred sites for obtaining filler and replacement material, which is, widely, used to increase the beaches when they are very eroded by coastal currents and beach drift. Ebb deltas are subject to a constant interaction between sea waves and tidal processes. Most of the time, their forms reflect these interactions. If the sea waves dominate the deposition environment, ebb deltas are smaller and distribute along the barrier-bars on one side and the other on the tidal cove. The largest ebb deltas form along the coastlines, where tides are strong, i.e., when tidal energy is more important than wave energy. The deposited sandy bodies can extend for several kilometres. If the energy of the environment is mixed, that is, from tides and waves, the ebb deltas have relatively poorly marked and rectilinear outside, while on the other side of the cove the delta geometry is branched. Ebb deltas dominated by the energy of the tides form elongated bodies, more or less, perpendicular to the inlet and with small high bottoms on each side. Ebb deltas can contain millions of cubic meters of sediment, which are very conducive to feeding the beaches. Recall that, taking into account the dominant forces in the formation process, Galloway classified the deltas into three main types: (i) River Dominated Deltas (dominated by the terrigeneous influx) ; (ii) Wave Dominated Deltas (dominated by the activity of sea waves) and (iii) Tidal Dominated Deltas (dominated by tidal activity and tidal currents). The river-dominated deltas are cut off and have many distributaries with marshes, bays or tidal flats in the inter-distributary regions. They occur when the river current and sediment transport are strong and other effects, such as rework by waves or tides, are smaller. These deltas tend to form large deltaic lobes in the sea, which may have little more than the distributary channel, and have a natural marginal dike (levee) exposed above sea level. Due to their resemblance to a bird's foot, they are often referred in the geological literature as a "bird's foot delta," as is the case with the Mississippi River Delta Building. When much of the floodplain between the distributary channels is exposed above sea level, the delta displays lobate form. Wave Dominated Deltas are more regular. They exhibit curved and arched shapes with beach ridges (berms), as in the Nile delta and Niger delta buildings, where the breaking causes a mixture of fresh and salt water. The flow loses, immediately, its energy and deposits all its load along the coast. Tidal Dominated Deltas occur in areas with high tides or with high speeds of tidal currents. Such deltas often resemble an estuarine bay filled with many elongated islands parallel to the main tidal current and perpendicular to the shoreline, such as the Brahmaputra Delta and the Mahakam Delta buildings . The delta buildings of the Mississippi and Yukon rivers are typical examples of the deltas dominated by the terrigeneous influx carried by the river. The delta buildings of the Senegal and San Francisco rivers are mainly dominated by sea wave activities, while the delta building of the river Fly is dominated by the action of the tides and tidal currents.
(*) Finger delta with the development of fan-shaped channels induced by a predominant fluvial dynamics.
Eccentricity (Earth's orbit).................................................................................................................................Excentricité (De l'orbite terrestre)
Excentricidade (órbita terrestre) / Excentricidad (de la órbita terrestre) / Exzentrizität (Astronomie) / 軌道離心率 / Эксцентриситет (отклонение от центра) / Eccentricità orbitale /
Distance from the ellipse of the Earth's orbit to one of the foci. The Earth rotates slowly around the Sun, but its orbit changes. The eccentricity of the Earth's orbit increases and decreases periodically. The change periods are 60 and 120 ky. A period of eccentricity of 400 ky is also known. The rotation of Earth's orbit has the same consequences as precession ; their effects can be added.
See: « Milankovitch's Cycle »
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« Precession »
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« Glacio-Eustasy »
In order to avoid misunderstandings it is good to recapitulate some basic data: (i) The Sun " borns" at East, "rises" and "sets" at West (in reality, since around 500 years we known that the Sun does not born, because it is the Earth that orbits around the Sun, at a speed of about 30 km s, but anyway ...) : (ii) It could be said that Earth's movement is from West to East, since the stars and the Sun "borns" in the East and "sets" at West ; (iii) If we look Northward, the polar star and the other stars move in the opposite direction to the needles of a clock ; (iv) If we look to the Southward, the movement is in the same direction as the needles of a clock ; (v) This motion is an apparent, because it is not the stars that move, but us ; (vi) As the stars move from East to West, the Earth must turn backwards, i.e., from West to East ; (vii) If we could see the Earth at the vertical of the North Pole, out of the atmosphere, we would see the Earth rotating in such a way that Asia would be to our right and 6 hours later it would be ahead of us and six hours later would be at our left, which means we would see the Earth rotates left to right ; (vii) The Earth rotates upon itself, in the opposite sense, the movement of the needles of a clock (Eastward) around an axis that intersecting the Earth's surface, determines the North and South geographic poles. In addition to these basic points all geoscientists know the Earth orbits the Sun once for every 366.26 rotations on its own axis, which is equivalent to 365.26 solar days or a sidereal year. This means that the Earth realizes a movement of translation around the Sun from the West to the East describing an elongated ellipse in 365 days and six hours. The eccentricity of the Earth's orbit or orbital eccentricity* varies, periodically, from a minimum of 0.01 to a maximum of 0.07. The average periodicity of eccentricity is 100,000 years, ranging from 90,000 years to 120,000 years. As the eccentricity of the Earth's orbit is very small, it alone does little to affect the amount of total solar energy (deviations of the order of 0.2%) received per year by Earth. However, its influence can be added to those created by other variations of the orbital parameters. In any case, the increase in the eccentricity of the Earth's orbit causes the increase of the summer/winter contrast in one hemisphere and the reduction of this contrast in the other, depending in each case of the seasons of the year in which aphelion and perihelion occur. If in a hemisphere the summer coincides with perihelion and the winter with aphelion then eccentricity is higher. The solar radiation during summer will be very intense and solar radiation in winter will be very weak. On the contrary, in the other hemisphere, the seasonal contrasts are very attenuated. The summer will coincide with the aphelion and the winter with the perihelion (http://mitos-climaticos.blogspot.ch/2005/05/excentricidade-da-rbita.html). As suggested in this figure, the eccentricity of the Earth's orbit has a great influence on the energy received from the Sun and therefore on the climate. The rotation of the Earth's orbit around the sun has the same consequences as precession (a physical phenomenon that consists in changing the axis of rotation of an object). During periods of great elongation, the Earth at the ends of the orbit is, particularly, far from the Sun. Both hemispheres receive abnormally low amounts of solar energy. On the other hand, when eccentricity is small, and especially when it is combined with an opposite inclination of the axis of rotation of the Earth, it creates very pleasant climatic conditions in the Northern Hemisphere. The mechanics of the orbits require the duration of the seasons be proportional to the area of the earth's orbit swept between the solstices and equinoxes. Solstices are moments in which the light of the sun strikes more intensely on the northern hemisphere and the southern hemisphere, so we speak of summer solstice in June and winter solstice in December. Equinoxes are moments when the light of the sun strikes with greater intensity in the equator, are intermediate stages between the summer solstice and the winter solstice and it is spoken of spring and autumn equinox. When the orbital eccentricity is very large, the seasons that occur on the far side of the orbit (aphelion) can be much longer. At present time, the eccentricity is close to the minimum (difference of 0.014%), so in the Northern Hemisphere, autumn and winter occur in the nearest part (perihelion), that is to say, when the Earth travels with a maximum speed.
(*) Amount by which the orbit around another body deviates from a perfect circle. The orbital eccentricity is, usually, represented by values between 0 and 1, although values greater than 1 can be observed in some comet orbits or space probes. A circular orbit has an eccentricity of 0 (e = 0). An elliptical orbit has an eccentricity between 0 and 1 (0 <e <1). A parabolic orbit has an eccentricity of 1 (e = 1). A hyperbolic orbit has an eccentricity greater than 1 (e > 1).
Ekman Movement............................................................................................................................................................Mouvement d'Ekman
Movimento de Ekman / Movimiento de Ekman / Bewegung Ekman / 埃克曼运动 / Ветровое движение жидкости (модель Экмана) / Movimento di Ekman /
Movement of the sea surface at 45° from the prevailing wind direction. This angle is caused by the combination of wind movement and Coriolis effect. The surface layer of sea-water entrains the underlying layer, which is further diverted than the surface layer. The deflection of water movement increases with depth and forms the Ekman spiral.
See: « Coriolis Effect »
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« Ekman Transportation »
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« Fair Weather Wave Base »
The sea currents are instigated by the wind. The effects of the currents is to move the hot water to the poles and cold water to the equator. The main factor in the movement of ocean water is the Coriolis effect. The Coriolis effect is produced by the Coriolis force, which appears, apparently, to be caused by the Earth's rotation, since all bodies moving on its surface are diverted to the right, in the Northern Hemisphere, and to the left in the Southern Hemisphere. To better understand the effect of Coriolis, think about the movement of a projectile launched by a piece of artillery. The projectile moves in a straight line. However, as the Earth rotates below it, an observer on the Earth's surface sees the projectile drift to the right (Coriolis effect). The same happens with air currents or water since they are not completely fixed on the Earth's surface. On the other hand, as shown in this figure, when the wind blows in a certain direction, the surface currents, due to the Coriolis effect, are diverted 45° (to the right in the northern hemisphere and to the left in the southern hemisphere). The velocity vector is, increasingly, diverted, as the depth increases, until it is oriented in the opposite direction to the wind (depth of friction). The end result of this process is that the water, in depth, moves perpendicular to the wind direction towards the centre of a spiral or whirlwind, which causes a slight excess or accumulation of water (10/20 m in height ) in the centre of the spiral. These water accumulations, under the gravity influence, flow out of the swirl, but the Coriolis effect diverts the flow to the right until it is parallel to the accumulation. At the point where gravity and the effect of Coriolis are compensated, the geostrophic currents are formed. That is why the big swirls are centred around 30° north and south of the equator. Ekman's pumping is the transport upward of sea water under the effect of depressed surface winds (closed zone of low atmospheric pressure relative to the pressure of the surrounding areas at the same level). Under the effect of the wind, the water between the surface and the thermocline displaces and is deflected by Coriolis force to the outside of the depression. This creates a divergence. The water layer at the centre of the depression is less thick and to compensate for this loss of mass, the deep water rises to the surface (Eckman pumping), propelled by the pressure of the water columns external to the depression. The horizontal and vertical movements of the water, in this case, produce either a depression (divergence) or an elevation (convergence). A depression in the Northern Hemisphere, and elevation in the Southern Hemisphere, since the direction of the wind around a depression and Coriolis force are inverted in both. Summing up: (i) The Coriolis effect corresponds to the change of course of any moving body on the Earth's surface, to the right, in the Northern Hemisphere and to the left in the Southern Hemisphere, due to the rotational direction and velocity of the Earth, which near the equator is, more or less, 1,666 km/h, but which has decreased towards the poles ; (ii) The vertical circulation of ocean currents can be induced either by the action of the winds (resurgence) or by the differences in seawater density (thermohaline circulation) ; (iii) In certain regions of the oceans, water can move vertically to the surface or to the sea floor as a result of surface-winded circulation that carries water away from or towards these regions ; (iv) This upwelling phenomenon is characterized by the rise of deep, generally, cold nutrient-rich water in certain regions of the ocean which, as a consequence, have, generally, high primary productivity, which may later favour the development of potential source- rocks ; although much of the vertical circulation of water in the oceans is, mainly, related to changes in surface water density ; (v) An increase in density may occur due to water cooling ; excessive evaporation over rainfall or ice formation and consequent increase in salinity of surrounding waters.
Ekman Spiral............................................................................................................................................................................................Espiral de Ekman
Spiral d' Ekman / Espiral de Ekman / Korkenzieherströmung / 埃克曼螺旋 / Экмановская спираль / Spirale di Ekman /
Helical variation of the velocity vector of a marine current in depth, function of the Coriolis effect.
See: « Coriolis Effect »
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« Ekman Transportation »
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« Contourite »
In the sea, the wind controls just the upper surface waters. The water layers underneath the upper moving layer undergo a traction (via friction). They are deflected due to the Coriolis effect (to the right in the Northern Hemisphere and to the left in the Southern Hemisphere). The next interval undergoes traction of the overlying layer, though not so strong. It moves, but it is also deflected. As illustrated in the right diagram, descending into the water column, all intervals or layers of water are deflected and move more and more slowly. The base layer of this spiral, called the Ekman spiral, can move in the opposite direction to that of the surface layer. In other words, it can be said: (i) The surface currents are influenced by the Coriolis effect ; (ii) The surface flow is deflected 45° with respect to the wind direction due to the Coriolis effect ; (iii) The velocity vector is, increasingly, diverted as the depth increases ; (iv) At the friction depth, the velocity vector is oriented in the opposite direction of the wind direction; (v) As the magnitude of the velocity vector decreases with depth, the effective transport, called the Ekman transport, is 90 ° (to the right in the Northern Hemisphere and to the left in the Southern Hemisphere) of the wind direction ; (vi) The velocity vector forms a spiral, called the Ekman spiral, which has a positive helical geometry in the Northern Hemisphere and negative in the Southern Hemisphere. When the wind causes a movement of surface water offshore (away from the coastline), the water moves vertically upwards. On the contrary, when the wind forces the surface of the water to move to the coastline, the surface water moves vertically downwards. When the wind blows from North to South, the surface water moves west, that is, away from the coast (Northern Hemisphere). An upward current (up-welling) brings back to the surface cold water. Surface waters are, usually, poor in nutrients (phosphates and nitrates, etc.), which are critical to plant growth. Deep and cold waters have high concentrations of these nutrients. In paleogeographic reconstructions it is important to determine the direction of the prevailing winds, since they may have an influence on the development of marine source-rocks, in particular on the divergent margins. If along a margin the dominant direction of the wind causes surface water to move offshore (beyond the edge of the platform), the bottom of the water column will move, vertically, upwards and bring for the platform oxygen and nutrients that will favour the development of the fauna and the flora in the platform, sina qua non condition for the formation of source-rocks. In order to understand the effect of Coriolis we must not forget that: (i) All points of the Earth's surface have the same angular velocity* and Coriolis force acts on all bodies ; (ii) A point near the equator rotates faster than a point near the north or south pole ; (iii) Objects on the floor, such as a house, rotate at the same speed as the floor ; (iv) Coriolis force has no effect on fixed objects on the ground ; (v) The speed at which a person is and the speed of the point to which he goes are very close to make him feel any difference ; (vi) If the angular velocity of an object at the surface of the Earth, relative to the rotational system (Earth), is zero, the Coriolis force is zero ; (vii) If an object moves south or northward and is not firmly attached to the ground, it maintains its initial velocity (Earth's rotational speed) as it moves ; (viii) If the object travels to eastward, it continues to move eastward with the same speed until a force is exerted that changes its speed ; (ix) Objects thrown from the equator to the north maintain the east component of the velocity in the same way as the objects standing on the equator ; (x) When an object distances itself far enough from the equator, it does not move further eastward with the same speed as the ground under it (for the rotational motion of rigid bodies, where the angular velocity is constant, the linear velocity is directly proportional to the radius) ; (xi) If a person without walking throws a ball to the East, the ball moves in a straight line (gravity omitted) ; (xi) If the person moves to a new position, the definition of East for him has changed and the ball does not move further east-west, the ball seems to have strayed out ; (xii) As the person does not feel the rotation of the Earth, the natural conclusion is that a mysterious force took the ball off its path causing it to move away from the axis of rotation (http: //www.geografia.fflch .usp.br / graduation / support / Support / Support_Elisa / flg0355 / filespdf / For% C3% A7a_de_Coriolis. pdf). Thus, in the same way, when a small mass of air begins to move under the effect of the forces of pressure, the Coriolis force comes into play and deflects its trajectory to the right if the movement occurs in the Northern Hemisphere and for the left if it passes in the southern hemisphere. This deviation will continue until the force of Coriolis balances the force created by the differences of pressure. In this case, the wind will follow the curves of equal pressure and the circulation is geostrophic.
(*) Rotation speed measurement, which is defined as the angle rotated by a unit of time. It is designated by the Greek letter ω. In the International System, its unit is radian per second (rad/s). At the equator, the latitude is zero. For other points above or below the equator, the distance to the axis of rotation of the Earth is smaller. Since the latitude of an Earth location is the angle measured from the equator line to that location, knowing the latitude, it is possible to determine the distance from such a location to the axis of Earth's axis rotation. As latitude increases, the distance from the point to the axis of rotation of the Earth decreases, as does the linear velocity, since it is proportional to the distance.
EkmanTransportation.............................................................................................................................................Transport d'Ekman
Transporte de Ekman / Transporte de Ekman / Ekman-Transport / 埃克曼运输 / Движение Экмана / Transporto di Ekman /
The amount of water carried by a marine current as a function of depth, since it decreases in depth due to the Coriolis effect. The variation of the velocity vector of a marine current in depth (function of the Coriolis effect) is the Ekman spiral.
See : « Geostrophic Current »
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« Coriolis Effect »
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« Wave Base »
A pseudo-force or inertial force is not a real force, but a correction that is added in such a way as to transform a non-inertial physically referential (coordinate system, which Newton's laws are not respected) into a theoretical inertial frame of reference, so that Newton's laws provide a correct description of what is observed from the non-inertial frame. Given an inertial frame, which respects Newton's law (a nonforce particle is either standing or moving in a straight line with constant velocity), another frame will be non-inertial when describing an accelerated motion in relation to the first . All referentials (coordinate system) in which Newton's laws of motion, particularly his first law, are valid are called inertial frames. These frames may be in motion relative to each other, but their relative motion is at a constant velocity. It is worth here to compare an inertial frame with a non-inertial frame. A car traveling at a constant speed of 50 km/h in the same direction can be considered as an inertial reference. If the driver of the car, suddenly, apply the brakes while the car decelerates it becomes a non-inertial frame. All objects inside the car suddenly accelerate (in relation to the car) even if no force is applied. A passenger in the front seat who has not fastened the seat belt is accelerated from the seat and injected through the windshield of the car. The law of inertia (Newton's first law) is violated in this reference (because the passenger accelerated without any force acting on it) and so the car became a noninertial reference. (N. Spielberg and BD Anderson, 1987- Seven Ideas That Shook The Universe John Wiley & Sons, Inc. ISBN 0-471-848-16-6). These notions are very useful for understanding the effect of Coriolis (when an object is in motion relative to a non-inertial frame) which is perpendicular to the speed and axis of rotation of the non-inertial system relative to the inertial. At sea, surface currents are influenced by the Coriolis effect. The surface flow is diverted by 45° (to the left in the Northern Hemisphere and to the right in the South) in relation to the wind direction due to the Coriolis effect. The velocity vector is shifted more and more as the depth increases until it reaches the depth of friction where it reaches a direction opposite to that of the wind. As the magnitude of the velocity vector decreases with depth, Ekman's transport is 90° (to the right in the northern hemisphere and to the left in the south) of the wind direction. The velocity vector* forms the so-called Ekman spiral which has a positive polarity in the northern hemisphere and negative in the southern hemisphere. Th Ekman spiral is a logarithmic spiral representing the theoretical hodograph (by immersion) of the longshore drift, which is induced by the tension of a permanent wind, which blows to the surface of the homogeneous sea of infinite depth, and submits to the effect of Coriolis). The formation of submarine valleys (as illustrated in this figure), which unlike submarine canyons** are not associated with any fluvial / deltaic system up-dip, becomes almost evident. The origin of submarine valleys, very common on the continental slope of West Africa, seems to be associated with the deflection of upward currents induced by the Coriolis effect. The deep currents are created by the pressure gradient towards the continent resulting from the surface currents piloted by Ekman's movement (a phenomenon first observed by the 1922 Nobel Peace Prize, Fridtjof Nansen, who noticed during his expedition to the Arctic in 1890, that the ice moved with a certain angle with respect to the direction of the wind). Over time, the movement of the surface waters, created by the wind, propagates in depth, but the speed decreases and the direction changes due to the effect of Coriolis. Ekman transport can induce downward or upward currents that carry water away from or near the basin edge. Erosion associated with upward currents (upwellings) creates the submarine valleys along the offshore continental slope of the Congo and Gabon, independently of any river system. The position of these valleys varies with time, as a function of Coriolis deflection. When the erosion reaches the top of the upper slope and the continental edge, an initiation of turbiditic currents is possible.
(*) The hodograph of the motion of a particle is the curve described by the extremities of the instantaneous velocity vectors when translated to have all the same origin.
(**) Although the formation of submarine canyons can be explained by many mechanisms, two different conjectures are, usually, advanced to explain their origin: (1) Submarine canyons dug by rivers whose mouths prograde seaward during periods of lowstand and (2) Submarine canyons that were dug by dense turbidity currents and with great erosive capacity, which can carry over 300 kg/m 3 and reach speeds exceeding 100 km/h. Unlike the first in this case, the geological conditions are, generally, highstand, i.e., the sea level is higher than the basin edge. The canyons of the first conjecture are the transport zones of the sedimentary particles of the turbiditic currents in the P. Vail model, while the latter explain better the turbiditic systems of E. Mutti.
Ecliptic................................................................................................................................................................................................................................................Écliptique
Eclíptica / Eclíptica / Ekliptik / 黄道 / Эклиптика / Eclittica /
Apparent trajectory that the sun traces in the sky for a year, which apparently moves eastward on an imaginary spherical surface (celestial sphere), relative to almost all fixed stars.
See: « Sun »
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« Milankovitch's Cycle »
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« Astronomical Theory of Paleoclimate »
From the geocentric point of view, the ecliptic is the great circle in the celestial sphere, which represents the annual trajectory of the Sun, seen from Earth. From a heliocentric point of view, the ecliptic is the intersection of the celestial sphere with the plane of the ecliptic, which is the geometric plane that contains the Earth's orbit around the Sun. Most of the planets in the solar system have an orbit that is a little inclined in relation to the plane of the ecliptic. The zodiac (the region of the sky around the ecliptic, divided into thirteen constellations, which corresponds to the twelve signs, where, seen from the Earth, the Sun, the Moon and the planets of the solar system move) is next to the plane of the ecliptic. The plane of the ecliptic is inclined to the celestial equator of an angle called the obliquity of the ecliptic, which is about 23° 27 '. This angle underlines the inclination of the axis of rotation of the Earth* in relation to the perpendicular to the plane of its orbit. The obliquity of the ecliptic corresponds to the position of the Earth in its orbit at the spring equinox. It is the starting point of the angular measurements of the ecliptic. As for the orbital plane of the Moon, it is inclined about 5° to the ecliptic. Since there are about 365.24 days in a year and 360 degrees in a circle, the Sun seems to move along the ecliptic at a rate of about 1° per day. This movement from West to East is contrary to the apparent east-west movement of the celestial sphere. The ecliptic and the celestial equator intersect at two points, directly vis-a-vis each other. The equinoxes are the moments when the Sun is at these points, which means from the heliocentric point of view, that the Earth is situated on one of these points of its orbit. On such occasions, day and night, each lasts about 12 hours, in all places of the Earth. One of these intersections is called the vernal point, which corresponds to the position of the Earth in its orbit at the time of the spring equinox. It is the point (point of Aries that is opposite the Point of Libra) from starting to the angular measurement points of the ecliptic. The point on the ecliptic, which is the most northerly of the celestial equator is called summer solstice in the northern hemisphere and winter solstice in the southern hemisphere. These names are inverted when the sun is to the south of the celestial equator.
(*) According to the large majority of geoscientists, the inclination of the axis of rotation of the Earth is the result of a collision between Earth and an asteroid at the beginning of the formation of the planets.
Ecology....................................................................................................................................................................................................................................................Écologie
Ecologia / Ecología / Ökologie / 生态 / экология / Ecologia /
Science that studies the relationship of living beings with each other and with the environment.
See: « Paralic »
Ecozone..................................................................................................................................................................................................................................................Écozone
Ecozona / Ecozona / Ökozone / 生物地理分布区 / Экозона / Ecozona /
Biogeographic domain of the Earth's surface based on patterns of historical and evolutionary distribution of terrestrial plants and animals.
See: « Animalia »
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« Paleontology »
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« Biostratigraphy »
The Earth's surface is divided into eight major ecozones, which are often called subregions or realm: (i) Afrotropical with 22.1 million km2 which can be subdivided into sub-Saharan Africa and Madagascar ; (ii) Antarctic with 0.3 million km2 ; (iii) Australasian with 7.7 million km2; (iv) Indo-malayan with 7.5 million km2 ; (v) Paleoarctic with 54.1 million km2 ; (vi) Neo-arctic with 22.9 million km2 ; (vii) Neotropical with millions of km2 ; (viii) Oceanian 1.0 million km2. The Paleoarctic and Neoartic ecozones form, for certain geoscientists, the Holoarctic ecozone. These ecozonas are characterized by the evolutionary history of the plants and animals they contain. As such, they are different from biomes also known as the main habitat types (space that has the right conditions for a species to reside ans reproduce, i.e., to perpetuate its presence), which are divisions of the Earth's surface made in the basis of the way of life, or in the adaptation of plants and animals to climatic conditions, soil, and other conditions. Biomes are bioclimatic areas or biotic areas, which correspond to a particular part of the planet that shares climate, vegetation and fauna. As illustrated in this figure representing the terrestrial ecozones of Canada, each ecozone can include a number of different biomes. A humid tropical rainforest in Central America, for example, may resemble a New Guinea biome in its structure and type of vegetation, climate, soils, etc., but the two forests are inhabited by plants and animals with different evolutionary histories. Ecozones are commonly used in zoo-geography. They are adapted to understand the distribution of mammalian fauna today. However, they are less relevant in other biogeographical disciplines. For birds (migratory species), the Paleoarctic is separated into two parts at the level of the Ural Mountains and the Caspian Sea. The Western Paleoarctic ecozone, where the migration of birds takes place southward to the Afrotropical ecozone and the Eastern Paleoarctic where the migration takes place southward to the Indomalayan and Australasian ecozones. As illustrated in this figure, the terrestrial ecozones of Canada are: (i) Arctic Cordillera ; (ii) Northern Arctic; (iii) Southern Arctic; (iv) Taiga Cordillera ; (v) Boreal Cordillera; (vi) Taiga Plains ; (vii) Taiga Shield ; (viii) Boreal Plains ; (ix) Hudson Plains ; (x) Boreal Shield; (xi) Atlantic Maritime ; (xii) Mixed-wood Plain; (xiii) Prairies; (xiv) Montane Cordillera and (xv) Pacific Maritime.
Elastic Rebound...........................................................................................................................................................Réajustement élastique
Reajustement elástico / Reajustamiento elástico / Elastische Nachjustierung / 弹性回跳 / Упругое отскакивание / Rimbalzo elastico /
Movement along a fault plane resulting from the abrupt release of a progressively increasing elastic tension between the rocks on either side of the failure plane.
See: « Trap (oil, gas) »
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« Footwall »
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« Fault »
In geology, the hypothesis of elastic rebound was the first conjecture, which explained, satisfactorily, earthquakes. Previously, contrary to the hypothesis of elastic rebound, it was thought that the failures on the Earth's surface were the result of the strong vibration of the Earth. After the 1906 earthquake in San Francisco, geoscientists examined the displacement of the terrain around the St. Andrew fault which separates two lithospheric plates. They concluded that the earthquake must have been the result of the elastic readjustment of the deformation energy accumulated on each side of the fault plane. In plate theory, lithospheric plates move relative to one another, except in areas where they are blocked. If a road crosses, orthogonally, the plane of one of these faults, as illustrated in this scheme, initially (Time 1), the road is perpendicular to the trace of the fault plane at point E, where the fault movement is blocked. Over time, the relative motion of the two plates, which in this case define the Saint Andrew fault, forces the rocks and road asphalt to increase the elastic deformation in the region where the fault is blocked, as illustrated in Time 2. This deformation is done at a rate of a few centimeters per year, but for many years. When the deformation is sufficiently large to overcome the resistance of the rocks, an earthquake occurs. During the earthquake, the portions of the rocks around the plane of failure that were locked, and that did not move back like a spring, released the displacement in a few seconds (Time 3) what the plates did between the time period 1 and Time 2. The time period between Time 1 and Time 2 can be from months to hundreds of years, whereas between Time 2 and Time 3 is seconds. As an elastic band, the more the rocks are deformed, the more elastic energy is stored and the more important the earthquake will be. The stored energy is released during the rupture, mainly in three ways: (i) As heat ; (ii) Damaging the rocks and as (iii) Elastic waves.
Elasticity..........................................................................................................................................................................................................................................Élasticité
Elasticidade/ Elasticidad / Elastizität / 弹性 / Эластичность (упругость) / Elasticità /
In a generic sense, it is the percentage change of a variable, given the percentage change in another, coeteris paribus (all else is constant). Elasticity is synonymous with sensitivity, response, reaction of one variable, in the face of changes in other variables.
See: « Kirchhoff-Bunsen Theory »
Electric Log.....................................................................................................................................................................................Diagraphie électrique
Diagrafia eléctrica / Perfil eléctrico, Log / Elektro-Log, Elektrische Protokollierung / 电测井, 电动日志 / Электрокаротажная диаграмма / Logging, Registro elettrico /
Generic term for all diagrams that illustrates measurements of induced or potential currents in the rocks of an exploration well, usually without casing.
See: « Dipmeter Log »
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« Radioactivity Log »
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«Sonic Log »
At present, most logs are interpreted automatically. They give a continuous reading of the lithology, porosity and percentages of the various fluids present in the pores. Although such logs seem very convincing, especially when presented in colour, it is preferable to always check the original data and, above all, to check them with the nonelectric logs made during the drilling. Most automatic interpretations do not take into account the presence of aberrant minerals, which can invalidate the whole process of interpretation. The presence of abundant mica reeds in a sand will be read by autolithic-logs as shales which will give wrong porosity values and the sand (potential reservoir-rocks) will be automatically interpreted as a packet of shales with no reservoir-rock quality. In my professional career, I found several errors of this type, especially those induced by the presence of glauconite. This mineral, which is very abundant in the transgressive sandstones, which are, in general, high quality potential reservoir-rocks and that, above all, can form potential stratigraphic traps (due to its retrogradational geometry), greatly influences the readings of the logs to such an extent that the sands can be mistakenly interpreted as clay intervals. The diagrams may also be used to determine lithology and the deposition environment. The spontaneous potential (SP) and gamma ray (GR) logs may indicate granulometry profiles (fining upward or coarsening upward) of the sandy intervals. The spontaneous potential logs are, locally controlled, by permeability, which increases with grain size. In this type of log, the maximum deflection to the left occurs in the most permeable intervals. The spontaneous potential, usually, registers a granulometry. The gamma ray can be used in a similar manner to indicate the clay content of the sand which, in general, increases when the particle size decreases.
Ellipsoid..........................................................................................................................................................................................................................................Ellipsoïde
Elipsóide / Elipsoide/ Ellipsoid / 椭圆/ Эллипсоид / Ellipsoid /
A quadratic surface analogous to an ellipse, which can be represented by an algebraic equation of the second degree *.
See: « Geodesic Sea Level »
(*) An equation of the second degree in the unknown x is of the form: a x² + b x + c = 0, where the real numbers a, b and c are the coefficients of the equation, with "a" nonzero. This equation is also called the quadratic equation because the term of greatest degree is squared.
Ellipsoid Heigh.................................................................................................................................................................................Hauteur ellipsoïde
Altitude Elipsoidal / Altura del elipsoide / Ellipsoid Höhe / 椭圆高度 / Эллипсоид высота / Altezza ellissoide /
Vertical distance of a point from the Earth's surface relative to a reference ellipsoid.
See: « Geodesic Sea Level »
Elongation (Astronomy, quadrature).....................................................................................................................................................................Élongation
Alongamento / Alargamiento (astronomía) / Elongation (Astronomie) / 距角 / Элонгация (удлинение) / Elongazioneß /
Angle, viewed from the Earth, between the direction of the Sun and the direction of a planet, which may be in an eastern or western elongation, depending on whether the planet is east or west of the Sun. The elongation of a higher planet ranges from 0° to 180°. The elongation of the lower planets varies between 0° and greater elongation (28° for Mercury and 48° for Venus). The term "lower planet" refers to the planets Mercury and Venus, which are closer to the Sun than the Earth, while "higher planet" refers to the planets Mars, Jupiter, Saturn, Uranus, Neptune and all planets minors and dwarves, including Ceres and Pluto, who are farther from the Sun than Earth.
See: "Quadrature "
Eluviation...................................................................................................................................................................................................................................Éluviation
Eluviação / Eluviación / Auswaschung / 淋溶 / Миграция растворённых веществ и коллоидов в водах верхних горизонтов / Eluviation /
Removal of dissolved or suspended material from one or more layers of soil by the movement of water when precipitation exceeds evaporation. Such loss of material in solution is often referred to as leaching. Eluviation, substantially, influences the composition of the soil.
See: « Soil »
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« Leaching »
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« Fragipan »
The term eluviation should not be confused with illuviation. The eluviation, which is driven by the downward movement of water in a soil, is the removal of organic and inorganic substances from a horizon by leaching, particularly on the A horizon of a soil. The illuviation, on the contrary, is the gradual accumulation of a layer of soil (or horizon) of several materials deposited by water infiltration (percolation). As shown in this scheme, the upper horizon (top of the soil), O horizon, is composed mainly of organic matter. Fresh garbage is found on the surface, while in depth all signs of the plant structure were destroyed by decomposition. The decomposed organic matter, or humus, enriches the soil with nutrients (nitrogen, potassium, etc.), favours the soil structure (binding the particles) and increases the retention of soil moisture. The second interval, under the surface horizon (horizon O), is formed by two horizons, A and E, which mark the beginning of the true mineral soil. At the top of the interval, the organic matter is mixed with inorganic weathering products and is therefore dark in colour due to the presence of organic matter. It is at the top of this range (horizon A) that eluviation, driven by the downward movement of water, is very active. The lower part (horizon E) is, usually, light in colour and eluviation is the dominant process. Leaching, or removal of clay particles, organic matter, and/or iron and aluminium oxides, is active in this horizon. Under the coniferous forests, this horizon often has a high concentration of quartz which gives it a gray colour. The third interval corresponds to the B horizon, which is an illuviation zone where the thin material moving downward is accumulated. The accumulation of this material forms a dense layer in the sun that is often enriched by nodules or levels of calcium carbonate. This occurs when carbonate is precipitated from water moving below ground or by capillary action.
Endobenthos (Organisms)..........................................................................................................................................Endobenthos (Organismes)
Endobentos / Endobentos (organismos) / Endobenthos (Im Inneren des Meeresbodens) / Endobenthos（海底室内） / Эндобентос (бентосные организмы) / Endobenthos (nell'interiore del fondo marino) /
Organisms that live within the sediments of the seabed. Many endobentos can move within the sediments, usually in the first 15 centimeters. The vast majority lives buried in the first two centimeters of the sea floor.
See: « Benthos »
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« Phytobenthos »
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« Infauna »
Endo-benthos are benthic organisms that live within the substrate that forms the sea floor or inland waters (lakes, for example). Examples of endo-benthos include Turritella, Aporrhais, Scrobicularia, Lingula, etc. Certainly, the best-known endo-benthos, especially of fishermen, is the lug-worm, which is also known as nereis (family of annelids). Although sandworms are not seen during low tide, since they live buried, they are much sought after by fishermen (dig the sand worm) to be used as fishing bait. The notion of endo-benthos and benthos is independent of the water-depth. In marine biology and limnology, benthos are organisms that live on the substrate (whether marine or inland) fixed or not, as opposed to pelagic organisms, which live freely in the water column. A typical example of benthos are corals. The benthos are subdivided into: (i) Phytobenthos, such as macroalgae, some microalgae and rooted aquatic plants ; (ii) Zoobenthos, animals and many benthic protists, which are formed by a) Macrofauna - animals visible to the naked eye, such as most crabs, echinoderms, insect larvae, worms, oligochaetes and some species of fish ; b) Meiofauna, animals that live permanently buried in the sediment, whether free or within structures built by them; many molluscs, such as clams, and various types of worms ; c) Microfauna,microscopic animals that develop on the substrate, mainly protists. Endobenthos are meio-fauna zoo-benthos. Function of the nature of the substrate (sand, mud, compact rock, etc.), the way of life of the benthos will be : 1) Epibenthic free (vagile); 2) Epibenthic fixed to the substrate and 3) Endobenthic (living inside the substrate). The hierarchy of endobenthic communities depends on the substrate, the excavator preference and the oxygen stratification of the interstitial waters.
Endogen (Plant).....................................................................................................................................................................................................Endogène (Plante)
Endógena / Endógena (planta) / Endogen / 内源 / Эндогенный (глубинный) / Endogena /
Plant that is developed by the growth of new cellular and vascular tissues from already formed tissues. The original meaning of "endogenous" is the inner growth next to a wall of outer cells. In a simpler way, endogenous is what is produced from within.
See: « Exogen »
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« Epifauna »
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« Phytoplankton »
An endogenous or endogene plant is a plant, which grows in size by internal growth and elongation at the summit, having a wood in the form of packages or topples, distributed, irregularly, along the whole diameter, without forming annual layers, and without medulla (soft and spongy tissue in the central part of the trunk). The leaves of the endogenous plants, usually, have parallel veins and the flowers are most often formed of three, or multiples of three, parts. The embryos have a single cotyledon (the first two leaves that emerge from the spermatophytes embryo, which produce seeds, and which burst forth during the germination of the seeds), with the first alternating leaves. The endogenous plants constitute one of the great classes of plants, and included plants like the palms, lilies, reeds, orchids, the banana, the pineapple, etc. Unlike an endogene plant, an exogene or exogenous plant is a plant that is characterized by having a bark and medulla, with the wood forming a layer between the bark and kernels. These plants grow, in their entirety, by the annual addition of a new layer of wood to the outside near the bark. The leaves have, usually, well-marked veins and the number of cotyledons is two, or, very rarely, several in a whirlpool. Seeds of mono-cotyledonous plants, such as orchids, palm trees, lilies, onions, garlic, etc., as the name implies, have only one cotyledon, while dicotyledons, such as peas, soy-beans, beans, strawberry, pear, coffee, apple, daisy, sunflower, orange, eucalyptus, avocado, rose, apple, cotton, cacao, lemon, etc., have two. In gymnosperms, which are vascular plants with unprotected seeds, i.e., plants without pulp, inserted in scales that form a more or less conical structure - pine cone, the number of cotyledons is variable. The gymnosperm plants (have root, stem, leaves, inflorescence in the form of pineapple and seeds) differ from the angiosperms, because these have the seeds wrapped by a fruit, generated by an ovary.
Endorheic (Hydrography)...................................................................................................................................................Endoréique (Hydrographie)
Endorreica / Endorreica (hidrografia) / Endorheisch / 内流盆地 / Бессточный (замкнутый) / Endoreico (idrografia) /
When drainage is not done directly to the sea, but to a basin. The hydrography is exorheic, if the drainage is made directly to the sea and arheic if there is no surface runoff and, finally, cryptorheic if the water line infiltrates the ground by sinks.
See: « Drainage Basin »
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« Exorheic (hydrography) »
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« Laguna »
The endorheic regions (internal drainage system) in contrast to exorheic regions, in which water flows into the ocean according to geologically defined patterns, are closed hydrological systems. The bottom of the endorheic basin is, usually, occupied by a salt or saline lake. About 18 percent of the area of the continents drains into lakes or endorheic seas. In the Earth, the largest of these areas is undoubtedly the interior of Asia. The surface waters are drained to the areas between mountains where they evaporate or seep into the soil, because they have not access to the sea. Endorheic waterbodies include some of the world's largest lakes, such as the Caspian Sea and the Aral Sea. The Caspian sea is the largest body of saline water in the world's isolated ocean water. Endorheic regions can occur in any climate, but are much more common in hot desert sites. In areas where precipitation is greatest, riparian erosion (erosion adjacent to the water stream) digs, usually, drainage channels (especially in the flood season) or increases the water level in the lakes until the water finds an outlet, breaking the geographic barrier of the endorheic (closed) hydrological system and opening it to the surrounding terrain. The Black Sea was, probably, a lake, with an independent hydrological system before the Mediterranean Sea flooded the terrain that separated them. A priori knowledge of the morphology and bathymetry of the Aegean Sea, Dardanelles Strait, Marmara Sea, Bosphorus Strait and Black Sea, allow to explain the "diluvium" or Noah's Flood flood. According to the hypothesis proposed by Ryan (1997), it would have been the result of the invasion of the Mediterranean into the Black Sea, about 7,000 BC, through the Bosporus. This hypothesis suggests that during the last glaciation the Black Sea was, partly, dry (endorheic water-body), and later, about 7,000 years ago, it would have been catastrophically filled, which would have produced a gigantic flood, i.e.,, the Deluge (universal flood, according to the Bible and the various traditions of the ancient Near East, that is to say, the area that, roughly, encompasses Western Asia).
Englacial Moraine..............................................................................................................................................................Moraine englaciaire
Moreia Englaciária / Morena englaciar / Moräne internen / 碛内部 / Внутренняя морёна / Morena interna /
All material stored inside a glacier. An englacial moraine, includes not only the material that falls into the glacier fissures (crevasses), but also the rocks that were ripped from the glacier bed.
See: « Moraine »
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« Glacier »
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« Ground Moraine »
In this photograph, the supraglacial moraine (material on the surface of the glacier, including lateral and medial moraines, and rock dust falling from the atmosphere) is falling into the crevasses of the glacier to form what glaciologists call the en-glacial moraine. It encompasses all the sediments stored and transported inside the glacier. Englacial and supraglacial moraines encompass the sediments that will later form the different types of moraines that can be highlighted in the glacial valley. The supraglacial moraines includes the sediments that will later form: (i) The terminal moraines ; (ii) The lateral moraines ; (iii) The medial moraines and (iii) the recessional moraines. The englacial moraine encompasses, also, all the sediments that are trapped inside the ice. Remember that the lateral moraines are formed by materials that fall on the glacier or that have been torn from the valley's walls. The lateral moraines may fuse. When two streams of ice converge they form a medial moraine. The ground moraine of the bottom are constituted by blocks and crushed material at the base of the glacier. The ground moraines can represent a very important volume of sedimentary material. A glacier deposits in front of him the materials that he transports and that form the great part of the supraglacial and en-glacial moraines. When, the sediments are deposited they form the terminal moraines, which certain geoscientists call frontal or "moraine valley". However, it should not be forgotten that the terminal moraine is deposited only when the front of the glacier come to rest in a certain place for a long enough time for the transported sedimentary particles settle. When a glacier is in a thickening phase, it slowly pushes the terminal moraine down the slope until it stops and starts thinning. The abandoned sediments from the impulse moraine. When a glacier is thinning, the frontal moraine is abandoned and another type of frontal moraine is deposited (recessional moraine), if the front of the glacier come to rest. The principal types of moraines that create topographic forms are: (i) Lateral moraines ; (ii) Medial moraines ; (iii) Ground moraines ; (iv) Frontal moraines ; (v) Recessional moraines and (vi) Terminal moraines.
Enhanced Oil Recovery (EOR)..................................................................Récupération assistée du pétrole
Recuperação avançada de petróleo / Recuperación asistida de petróleo / Enhanced Oil Recovery, EOR, Enhanced Erholung (Öl) / 提高原油采收率 / Добыча нефти при поддержании давления / Recupero olio migliore /
Term applied to techniques and methods that increase the amount of oil that can be extracted from an oil field. Enhanced oil recovery (EOR) is, often, referred to as tertiary recovery (viscosity reduction to facilitate extraction) or improvised (as opposed to primary and secondary). With a EOR, 30-60% of the oil present in a rock-reservoir can be extracted compared to the 20-40% extracted during primary and secondary production.
See: « Pool (hidrocarbon) »
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« Petroleum »
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« Oil Recovery »
Oil production is separated into three phases: (i) Primary ; (ii) Secondary and (iii) Tertiary, which is also known as Enhanced Oil Recovery (EOR). Primary oil recovery is limited to hydrocarbons that rise, naturally, to the surface, or those that use artificial lift devices, such as pump jacks. Secondary recovery employs water and gas injection, displacing the oil and driving it to the surface. According to the US Department of Energy, utilizing these two methods of production can leave up to 75% of the oil in the well (https://www.rigzone.com/training/insight.asp?insigh t_id=313) The way to further increase oil production is through the tertiary recovery method or EOR. Although more expensive to employ on a field, EOR can increase production from a well to up to 75% recovery. Usually, gas injection is the most common method of enhanced oil recovery (EOR). However, other gases, such as CO2, natural gas or nitrogen, can be injected into the reservoir-rock, which, immediately, expand pushing additional oil into the production wells, as illustrated in the scheme above. At the same time, as these gases dissolve in the petroleum, they lower their viscosity, which significantly increases the flow rate. The displacement of the oil by CO2 depends on the behaviour of the CO2 phase and the oil mixtures, which are, extremely, dependent on the rock-reservoir temperature, pressure and composition of the oil. These mechanisms vary with increasing oil volume and reducing viscosity by injections of immiscible fluids (low pressure) up to the displacement, completely, miscible in high-temperature injections. In these applications, more than half, and in some cases two-thirds, of the injected carbon dioxide returns with the oil produced and is usually reinjected into the reservoir-rock to reduce the price of recovery operations. The remaining CO2 is sequestered in the rock-reservoir. It this reason, that presently, due to the ecological problems that some politicians and the media attach to CO2, that certain enhanced oil by of CO2 injection can be largely economic, particularly when the fields to be reactivated are located close to the industries which produce much CO2, such as refineries, power stations, etc. Other enhanced oil recoveries use heat to increase the flow rate and, more rarely, the injection of chemicals to increase the influence of the aquifer or to decrease the capillary pressure.
Enhanced Unconformity (Angular unconformity)......................................................Discordance angulaire
Discordância angular / Discordancia angular / Schräg-Diskordanz / 角度不整合 / Угловое несогласие / Discordanza angolare /
Unconformity in which the overlying layers have a different dip than the underlying layers, that is to say, that there is a tectonic phase between the two stratigraphic cycles that unconformity limits. Synonym of Reinforced Unconformity (by tectonics).
See: « Relative Sea Level Fall »
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« Truncation »
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« Disconformity »
Two tectonically enhanced unconformities (angular unconformities) are, easily, recognized on this tentative geologically interpretation of a Canvas auto-trace of a detail of an offshore seismic line from China. This offshore corresponds to the stacking of four types of basins of the classification of the sedimentary basins of Bally and Snelson (1980): (i) Basement, which probably corresponds, to a large extent, to Precambrian a folded belt ; (ii) Paleozoic flattened folded belt ; (iii) Mesozoic-Cenozoic back-arc basin, within which one can distinguish half-grabens, developed during a rifting phase, covered by sediment deposited during the sag or thermal phase, and (iv) Cenozoic non-Atlantic type divergent continental margin. A large Paleozoic sedimentary package was deposited over the basement, which is, probably, composed of rocks of Precambrian age, which later, due to successive compressional tectonic regimes, became a folded belt, which, at the end of the Paleozoic Era, became a peneplain. The Paleozoic interval is separated by a tectonically enhanced unconformity, i.e., an unconformity induced by a relative sea level fall and reinforced by tectonics, which is easy to recognize, taking into account the reflections terminations, particularly the toplap by truncation (upper terminations). The relative sea level is the local sea level, referenced to any point of the Earth's surface, which can be the sea floor or the base of the sediment and which is the result of the combined action of absolute or eustatic sea level (supposed to be global and referenced to the Earth's centre). Above this unconformity the sediments of the back-arc basin were deposited, whose beds have a very different dip. A new compressional tectonic regime shortened the rocks that were lifted and eroded. The erosional surface underlines a new peneplain that was covered during the Cenozoic by a non-Atlantic type divergent margin. The upper unconformity between the Paleozoic/Mesozoic sediments and the Cenozoic margin sediments is also an angular unconformity, although the overlying intervals are parallel to the unconformity and have a parallel internal configuration. In seismic terms, the acoustic impedance profiles, associated with all these angular unconformities, vary, laterally, as the interfaces, that define them, change laterally. These unconformities, on the contrary, to the unconformities not enhanced by tectonics, are not underlined by a homogeneous seismic reflector (more or less constant amplitude) and continuous, but by a lateral association of discontinuous reflectors with different characteristics, function of the acoustical impedance profiles. This type of unconformity can not be followed or picked (tracked) in continuity. The geoscientist is forced to jump from reflections crests to troughs or the opposite, every time the acoustical impedance contrast changes. It is in the interpretation of the unconformities and, in particular, of the tectonically enhanced unconformities, that the qualities of the interpreter are seen. On a seismic line and, particularly, within a sequence-cycle, the only seismic surface (area bounded by reflector terminations) which can be followed, more or less, continuously and over a relatively important distance is the downlap surface that separates the highstand prograding wedge (HPW) from the transgressive interval (TI). This seismic surface is not a chronostratigraphic surface but a diachronic surface, as the hiatus between the underlying interval (transgressive interval) and the overlying interval (highstand prograding wedge) increases seaward. It was for these reasons that a few years ago certain American geoscientists said, somewhat unhappily, that the picking of a tectonically enhanced unconformity is for men. In reality, all they wanted to say was that the picking of a tectonically enhanced unconformity requires a certain amount of knowledge and a certain experience which, in general, the beginner or novice geoscientists do not yet have. In conclusion, tectonically enhanced unconformities, although they are the easiest to recognize in field or seismic lines (taking into account the reflector terminations of the intervals they separate), are relatively rare and local, while the most frequent are cryptic unconformities, whose identification is made, above all, from the recognition of the submarine canyons and incised valleys fills.
Entrainment (Traction, rolling, dragging)................................................................................................................................................Traction
Arrastamento / Tracción / Zichen / 牵引 / Тяга / Trazione /
Displacement of large sedimentary particles from a river's charge along the river bed by entrainment, which can also be done by rolling the particles.
See: « Saltation (transport) »
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« Sediment Influx »
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« Sediment Bypassing »
Sediment transport by entrainment is one of many types of sediment transport. It is particularly frequent in water-courses. Most of the time, it is associated with saltation and suspension. However, in general, sediment transport varies with transport mechanisms which are dependent, among other things, on the sedimentary environment. The great majority of geoscientists admit five major types of transport mechanisms: (i) Aeolian ; (ii) Fluvial ; (iii) Coastal ; (iv) Glacial and (v) Sloping. In the first type, the sediments are carried by the wind. The sand dunes, both on the beaches and in the deserts are the typical result of this type of transport. Fluvial mechanisms are associated with the water flow in natural systems. This encompasses the rivers, brooks, periglacial flows, floods and floods induced by the rupture of the glacial lakes. The sediments carried by the water are larger than the sediments carried by the air, since the water has a higher density and viscosity. Larger sediments transported by rivers are typically sand and gravel, but during large floods, rivers can also transport pebbles and blocks. In coastal mechanisms, sedimentary transport occurs along the coastline and is mainly induced by the movement of sea waves and coastal currents. At the mouths of rivers, coastal and river sediments meet creating river deltas. These mechanisms are the basis of the formation of beaches and coastal strands. Glacial mechanisms are associated with the flow of glaciers, which can carry large sediments. The glacial deposition areas contain numerous erratic blocks, some of which have dimensions that can exceed several meters in diameter. The mechanisms that carry the sediments and the regolith* down the slope are, in particular, the creeping slow creep and the slides induced by the cavities created by the trees. Geoscientists reverse the interpretations of transport relationships to understand the depth, velocity and direction of the flows that induced sedimentary rocks and modern alluvial deposits.
(*) According to https://en.wikipedia.org/wiki/Regolito, a regolith is a loose layer of heterogeneous and superficial material that covers a solid rock. It includes dust, soil, broken rock and other related materials and is present on Earth, the Moon, Mars, some asteroids and other terrestrial planets and moons. On the moon, the surface-covering regolith is due to cosmic erosion, commonly referred to as atomization or weathering of rocks by sudden temperature fluctuations, collisions with other meteorites, or other physical processes.
Entropy.................................................................................................................................................................................................................................................Entropie
Entropia / Entropía / Entropie (Thermodynamik) / 熵 / Энтропия / Entropia /
Sometimes referred as the disorder of a system, but can also be defined in terms of imbalance. A system with a small entropy has a very large imbalance or important energy differences between different parts of the system. In a system with a large entropy, the different parts of the system are in equilibrium, since they have, more or less, the same level of energy* and therefore little work can be performed, since the energy can not flow from one place to another.
See: « Big Bang (theory) »
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« Inflationary Universe»
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« Systems' Theory »
Function that defines the state of disorder of a system. The total entropy of an isolated system must always increase. Its disorder** must always grow (2nd principle of thermodynamics ***). One of the ideas involved in the concept of entropy is that in isolated systems, nature tends to bring things of order to disorder. It is important to know how to define disorder if this term is used to understand entropy. The most accurate way to characterize entropy is to say that it is a measure of the "multiplicity" associated with the state of objects. If a given state can be achieved in various ways, then it is more likely than one that can be done just in one or two ways. For example, when throwing two dice (1 to 6), a seven (sum of two faces) is more likely than a two. A total of seven can be obtained in six different ways (1 + 6 ; 2 + 5 ; 3 + 4 ; 4 + 3 : 5 + 2 ; 6 + 1 ). There is only one way to get two (1 + 1). Thus, seven has a greater multiplicity than two. You can say that seven represents greater disorder or greater entropy. In the same way, if all regular and orderly arranged bricks of truck fall to the ground, it is evident that the most probable pile of bricks, which will form on the floor, is a disordered pile. The disordered pile is posterior to the ordered pile of bricks. An increase in entropy marks the arrow of physical time. In the scheme represented in this figure, the time direction is from the left (order) to the right (chaos). Fill a glass with ice cubes (time 1). The heap of ice cubes looks very messy, but the ice cubes impose limits on the number of ways in which water molecules can be arranged. When the ice cubes melt (time 2). The glass of water appears uniform and homogeneous, but the water molecules can be arranged in many other ways, they have a greater multiplicity. They a have a greater entropy. In all these situations, the initial state is more organized than the final state. The final situation contains less information than the initial state. The passage from the past to the future, from birth to death, defines the direction of psychological time. The transition from organization to disorder, from more information to less information, from imbalance to equilibrium, defines the direction of physical time.
(*) Energy is the ability to do a work and work is accomplished every time object is displaced by a force. More the object is displaced the greater is work, greater is the force more the work is important. Neither the work nor the heat is energy forms. Both are methods to transfer energy from one place to another... work is a method, heat is another. The energy can be transferred either through work or heat.
(**) In physics, disorder must grow, information must be lost, and imbalance must disappear.
(***) This principle was discovered in the nineteenth century, during the industrial revolution, when trying to improve the performance of steam engines.
Eolian System (Deposition)................................................................................................................................................................Système éolien
Sistema eólico / Sistema eólico / Wind Systems / 风力发电系统 / Эоловая система / Sistema eolico /
Deposition system that has wind, which is a poor erosion agent (but is effective in transporting loose sand, sludge and dust), as the main geological agent.
See: « Coastal Non-Marine Deposit »
Eolisation.....................................................................................................................................................................................................................................Éolisation
Eolização / Eolización / Windkorrosion / 风腐蚀 / Эолизация / Aeolizione /
Polishing effect caused by the corrosive action of the wind and the sand it carries, on the surface of rocks, stones and blocks, giving it a satin sheen or wind varnish. It can also mean, in a broader sense, the combined effect of corrasion and deflation, producing more or less characteristic forms.
See : « Erosion »
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« Aeolianite »
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« Corrasion »
Cailleux (1942) proposed a method of morphological analysis of sands. Based on the shape and appearance of quartz grains, he distinguished four fundamental categories: (I) Non-Worn (NW), angular ; (ii) Bright Polished (BP), which suggests a large and long work in an aquatic environment ; (iii) Clean Round (CR), worn by the wind ; (iv) Dirty Round (DR), old reworked wind grains. By establishing for a given sample, the percentage of each type, one can determine the history of grains and therefore the actions that were exerted on them. The result of such an analysis must be interpreted. One of the most important types of sand, formed of non-worn grains (NW), can be sand from a freshly disaggregated sand whose grains have not yet been worked. A sand containing a lot of bright polished grain (BP), they can be derived from an older marine material. Aeolisation can produce characteristic forms such as: 1) Mushroom rocks or pedestal rocks ; 2) Tafoni ; 3) Alveoli ; 4) Slickensides ; (5) Ventifacts. Mushroom rocks or pedestal rocks, i.e., mushroom-shaped or table-shaped blocks that appear to be linked to the abrasion of the underwater tidal currents or to wind erosion in the desert regions. They are an indicator of mean high tide level . Tafoni (singular: tafone) are cave-like features developed on sandy or crystalline rocks characterized by a spherical cavity excavation by deflation of the elements disaggregated by subcutaneous alteration, due to the corrosion, generally, induced by sea-spray (salt-spray).Their geographic distribution is not zonal. They form on all sandy littoral , in position exposed to the wind, and in semi-arid regions. Alveoli have a honeycomb pattern. Ventifacts are wind-blown and wind deflated pebbles with sharp edges, the number of which depends on the position of the pebble facing the winds and with perforated or polished faces in the part exposed to the wind. They appear on beaches and deserts
Eon.....................................................................................................................................................................................................................................................................................Éon
Éon / Eón / Äon (Geologie) / 宙 / Геологическая эра / Eone /
The first division of geological time. From the earliest to the most recent the eons are: (i) Hadean ; (ii) Arkeozoic ; (iii) Proterozoic and (iv) Phanerozoic.
See: « Geological Time »
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« Geological Time Scale »
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« Enothem »
In this geological scale, modified from Hunt (1990), the oldest Eon, is the Archaeozoic. Many geoscientists divide the Archaeozoic in Hadean and Archean and consider four aeons in the geological history: (i) Hadean ; (ii) Archean ; (iii) Proterozoic and (iv) Phanerozoic. The Precambrian, for certain geoscientists, is a Super-eon, and corresponds to the Archaean or Archaic, Archaeozoic and Proterozoic, while others consider, before Hadean, the Cryptozoic (Gamovian and Planckian). In this geological scale, in the last column is represented the percentage time since the beginning of each geological period (equivalent time of the system, that is, of the rocks) until today. Assuming that the bottom of the Archaeozoic represents the Earth's age (100%), the Neogene represents 0.6% of the Earth's total age. Conceiving in an abstract and intellectual way, time is very simple. All people know how many zeros must be join the number ten to represent one million years. On the contrary, assimilating such a period of time is much more difficult. All the kids today know that the dinosaurs disappear around 65 Ma, but they have no idea what that means. The notion of geological time is so strange that it can only be grasped by metaphors. "Let us imagine a yard, an old English measure, which is, roughly, the distance between the nose and the end of your hand when extended. If this distance (± 91 cm) represents the Earth's age, a simple filing at the nail of his thumb is sufficient to make the whole history of mankind disappear "(McPhee, J., 1980). "Man has been here on Earth for 32,000 years, and it has taken 100 million years to prepare the world for him, it is the proof that man was made to live here, I suppose, but I do not know. If we take the Eiffel Tower, in Paris, to represent the age of the world, the painting film that on top of everything, protects the top of the pinnacle, represents the human portion of that age and it is evident, for everybody, that the tower Eiffel was built just for this thin film of paint to be there. It is possible, but I do not know "(Mark Twain, 1903).
Eonothem...................................................................................................................................................................................................................................Énothème
Enotema / Enotema / Äonothem (Major stratigraphischen Einheit) / Enothem （主要地层团结）/ Энотема / Eonotema (major unitá stratigrafica) /
The greatest stratigraphic unit in Earth's history. There are three main enothems, which are constituted by erathems. In turn, the erathems are composed of systems, which are made up of series and these by several stages.
See: « Geological Time »
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« Biostratigraphic Unit »
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« Eon »
Certain geoscientists stress the fact that rocky units do not have an explicit time connotation. The time units equivalent to the rock units are shown in this figure. For example, the Cretaceous System is composed of all the rocks deposited during the Cretaceous Period. The Upper Cretaceous is not synonymous with Late Cretaceous. The Upper Cretaceous translates a set of rocks, which were deposited during the Late Cretaceous (time). When it is said that the Late Cretaceous corresponds to the time-interval between 100 and 65 Ma of the Earth's history, this does not mean that the time of deposition of the rocks, which form the Upper Cretaceous, is 35 My. The actual deposition time is much smaller than the total time of the geological interval. When the age difference between the boundaries of a sequence-cycle (induced by a 3rd order eustatic cycle, which has a duration between 0.5 and 3-5 Ma) is 2 Ma, this does not mean that time of deposition of the rocks that form the different sedimentary systems tracts of the sequence-cycle is 2 My. If the time difference between the boundaries of the submarine basin floor fans (SBFF), i.e., of all the turbiditic lobes forming the lower sub-group of the lowstand systems tracts group (LSTG), is 300 ky, it is evident that the effective time of deposition of the lobes is much smaller. Geologically, the time of deposition of a turbidite lobe is instantaneous. A lamination of a beach deposit is deposited in one second. A lamination of a hummocky cross-stratification of the storm deposits is deposited in a few minutes. A turbidite layer is deposited in a few hours. Flood deposits, such as the Scablands (associated with floods induced by the failure of retention of lakes behind the Plio/Pleistocene glaciers of Canada) deposit in a few weeks. Varves are deposited in one year. One centimetre of pelagic sediment is deposited in, more or less, 1 ky. A continental encroachment sub-cycle is deposited between 5 and 50 My, and a continental encroachment cycle between 50 and 200 My.
