NationMaster - Encyclopedia: Structure of the Earth

The interior of the Earth, similar to the other terrestrial planets, is chemically divided into layers. The Earth has an outer silicate solid crust, a highly viscous mantle, a liquid outer core that is much less viscous than the mantle, and a solid inner core. Many of the rocks now making up the Earth's crust formed less than 100 million (1×10⁸) years ago; however the oldest known mineral grains are 4.4 billion (4.4×10⁹) years old, indicating that the Earth has had a solid crust for at least that long.^[1] Most of the Earth's structure is theoretical, being based on extrapolations of physical evidence which has come from the first few kilometres of the earth's surface, samples brought to the surface from deeper depths and analysis of signals that pass through it in the Electromagnetic spectrum. Image File history File links This is a lossless scalable vector image. ... Image File history File links This is a lossless scalable vector image. ... This article is about Earth as a planet. ... A terrestrial planet or telluric planet is a planet which is primarily composed of silicate rocks. ... A chemical substance is any material substance used in or obtained by a process in chemistry: A chemical compound is a substance consisting of two or more chemical elements that are chemically combined in fixed proportions. ... The silicate minerals make up the largest and most important class of rock-forming minerals. ... Geologic provinces of the world (USGS) In geology, a crust is the outermost solid shell of a planet or moon. ... Earth cutaway from core to exosphere. ... Earth cutaway from core to exosphere. ... Although some radiations are marked as N for no in the diagram, some waves do in fact penetrate the atmosphere, although extremely minimally compared to the other radiations The electromagnetic (EM) spectrum is the range of all possible electromagnetic radiation. ...

Assumptions

The force exerted by Earth's gravity can be used to calculate its mass, and by estimating the volume of the planet, its average density can be calculated. Astronomy can also calculate the Earth's mass from its orbit and effects on nearby planetary bodies. Observation of rocks, bodies of water and the atmosphere allow estimation of the mass, volume and density of rocks to a certain depth, the remaining mass must be in the deeper layers.

Structure

The structure of the Earth can be visualised in two ways: chemically or by material properties. Chemically, the Earth can be divided into the crust, mantle, outer core, and inner core. By comparing material strength, the layering of the earth is categorized as lithosphere, asthenosphere, upper mantle, lower mantle, outer core, and the inner core. The geologic component layers of the Earth^[2] are at the following depths below the surface:

The layering of the Earth has been inferred indirectly using the time of travel of refracted and reflected seismic waves created by earthquakes. The core does not allow shear waves to pass through it, while the speed of travel (seismic velocity) is different in the other layers. The changes in the seismic velocity between the different layers causes refraction owing to Snell's law. Reflections are caused by a large increase in seismic velocity and are similar to light reflecting from a mirror. The tectonic plates of the lithosphere on Earth. ... Geologic provinces of the world (USGS) In geology, a crust is the outermost solid shell of a planet or moon. ... Earth cutaway from core to exosphere. ... This article does not cite any references or sources. ... Earth cutaway from core to exosphere. ... Cross section of the whole Earth, showing the complexity of paths of earthquake waves. ... Cross section of the whole Earth, showing the complexity of paths of earthquake waves. ... This article is about Earth as a planet. ... This article is about the natural seismic phenomenon. ... Refraction of light at the interface between two media of different refractive indices, with n2 > n1. ...

Core

The average density of Earth is 5515 kg/m³, making it the densest planet in the Solar system. Since the average density of surface material is only around 3000 kg/m³, we must conclude that denser materials exist within Earth's core. Further evidence for the high density core comes from the study of seismology. Earth, also known as the Earth or Terra, is the third planet outward from the Sun. ... Kg redirects here. ... This article is about the unit of length. ... Seismology (from the Greek seismos(ÏƒÎµÎ¹ÏƒÎ¼ÏŒÏ‚) = earthquake and Î»ÏŒÎ³Î¿Ï‚,logos = knowledge ) is the scientific study of earthquakes and the propagation of elastic waves through the Earth. ...

Seismic measurements show that the core is divided into two parts, a solid inner core with a radius of ~1220 km and a liquid outer core extending beyond it to a radius of ~3400 km. The solid inner core was discovered in 1936 by Inge Lehmann and is generally believed to be composed primarily of iron and some nickel. Earth cutaway from core to exosphere. ... This article is about an authentication, authorization, and accounting protocol. ... Inge Lehmann (May 13, 1888 - February 21, 1993), Fellow of the Royal Society (London) 1969, was a Danish seismologist who, in 1936, argued that the Earth must not only have a molten interior, but a solid core at the center, which deflects P waves. ...

In early stages of the Earth's formation about 4.5 billion (4.5×10⁹) years ago, melting would have caused denser substances to sink toward the center in a process called planetary differentiation (see also the iron catastrophe), while less-dense materials would have migrated to the crust. The core is thus believed to largely be composed of iron (80%), along with nickel and one or more light elements, whereas other dense elements, such as lead and uranium, either are too rare to be significant or tend to bind to lighter elements and thus remain in the crust (see felsic materials). Some have argued that the inner core may be in the form of a single iron crystal.^[3]^[4] In cosmogony, planetary differentiation is a process by which the denser portions of a planet will sink to the center; while less dense materials rise to the surface. ... To meet Wikipedias quality standards, this article or section may require cleanup. ... Geologic provinces of the world (USGS) In geology, a crust is the outermost solid shell of a planet or moon. ... For other uses, see Nickel (disambiguation). ... General Name, Symbol, Number lead, Pb, 82 Chemical series Post-transition metals or poor metals Group, Period, Block 14, 6, p Appearance bluish gray Standard atomic weight 207. ... This article is about the chemical element. ... Felsic is a term used in geology to refer to silicate minerals, magmas, and rocks which are enriched in the lighter elements such as silica, oxygen, aluminium, sodium, and potassium. ... For other uses, see Crystal (disambiguation). ...

The liquid outer core surrounds the inner core and is believed to be composed of iron mixed with nickel and trace amounts of lighter elements.

Recent speculation suggests that the innermost part of the core is enriched in gold, platinum and other iron-loving (siderophile) elements.^[5] GOLD refers to one of the following: GOLD (IEEE) is an IEEE program designed to garner more student members at the university level (Graduates of the Last Decade). ... General Name, Symbol, Number platinum, Pt, 78 Chemical series transition metals Group, Period, Block 10, 6, d Appearance grayish white Standard atomic weight 195. ... The Goldschmidt Classification, developed by Victor Goldschmidt, is a geochemical classification which groups the chemical elements according to their preferred host phases into siderophile (iron loving), lithophile (silicate loving), chalcophile (sulfur loving), and atmophile (gas loving). ...

The matter that is the Earth is connected in fundamental ways to the matter of certain chondrite meteorites, and to the matter of the outer portion of the Sun ^[6] ^[7]. There is good reason to believe that the Earth is, in the main, like a chondrite meteorite. Beginning as early as 1940, scientists, including Francis Birch, built geophysics upon the premise that the Earth is like ordinary chondrites, the most common type of meteorite observed impacting Earth, while totally ignoring another, albeit less abundant type, called enstatite chondrites. The principal difference between the two meteorite types is that enstatite chondrites formed under circumstances of extremely limited available oxygen, leading to certain normally oxyphile elements existing either partially or wholly in the alloy portion that corresponds to the core of the Earth. A specimen of the NWA 869 chondrite (type L4-6), showing chondrules and metal flakes Chondrites are stony meteorites that have not been modified due to melting or differentiation of the parent body. ...

It is generally believed that convection in the outer core, combined with stirring caused by the Earth's rotation (see: Coriolis effect), gives rise to the Earth's magnetic field through a process described by the dynamo theory. The solid inner core is too hot to hold a permanent magnetic field (see Curie temperature) but probably acts to stabilise the magnetic field generated by the liquid outer core. In the inertial frame of reference (upper part of the picture), the black object moves in a straight line. ... The magnetosphere shields the surface of the Earth from the charged particles of the solar wind. ... The Dynamo theory proposes a mechanism by which a celestial body such as the Earth generates a magnetic field. ... In physics, the Curie point, or Curie temperature, is the temperature above which a ferromagnet loses its ferromagnetic ability to possess a net (spontaneous) magnetization in the absence of an external magnetic field. ...

Recent evidence has suggested that the inner core of Earth may rotate slightly faster than the rest of the planet.^[8] In August 2005 a team of geophysicists announced in the journal Science that, according to their estimates, Earth's inner core rotates approximately 0.3 to 0.5 degrees per year relative to the rotation of the surface.^[9]^[10] Year 2005 (MMV) was a common year starting on Saturday (link displays full calendar) of the Gregorian calendar. ... Geophysics, the study of the earth by quantitative physical methods, especially by seismic reflection and refraction, gravity, magnetic, electrical, electromagnetic, and radioactivity methods. ... Science is the academic journal of the American Association for the Advancement of Science and is considered one of the worlds most prestigious scientific journals. ...

The current scientific explanation for the Earth's temperature gradient is a combination of the heat left over from the planet's initial formation, the decay of radioactive elements, and the freezing of the inner core. Other explanations include the georeactor hypothesis. penis, hahaha big long penis. ... Since the 1970s, geochemistry has documented the origin and existence of naturally occurring slow fission reactors, specifically in geologic formations at Oklo in Gabon, Africa. ...

Mantle

Earth's mantle extends to a depth of 2890 km, making it the largest layer of the Earth. The pressure, at the bottom of the mantle, is ~140 GPa (1.4 Matm). The mantle is composed of silicate rocks that are rich in iron and magnesium relative to the overlying crust. Although solid, the high temperatures within the mantle cause the silicate material to be sufficiently ductile that it can flow on very long timescales. Convection of the mantle is expressed at the surface through the motions of tectonic plates. The melting point and viscosity of a substance depends on the pressure it is under. As there is intense and increasing pressure as one travels deeper into the mantle, the lower part of the mantle flows less easily than does the upper mantle (chemical changes within the mantle may also be important). The viscosity of the mantle ranges between 10²¹ and 10²⁴ Pa·s, depending on depth.^[11] In comparison, the viscosity of water is approximately 10^-3 Pa·s and that of pitch 10⁷ Pa·s. Thus, the mantle flows very slowly. Earth cutaway from core to exosphere. ... Image File history File links No higher resolution available. ... Image File history File links No higher resolution available. ... Ordovician ophiolite in Gros Morne National Park, Newfoundland. ... The Gutenberg Discontinuity is the boundary which separates the Earths core and mantle. ... The Lehmann discontinuity, named after seismologist Inge Lehmann, is the boundary layer in between the liquid outer core and the solid inner core. ... Earth cutaway from core to exosphere. ... This article is about pressure in the physical sciences. ... For other uses, see Pascal. ... Atmospheric pressure is the pressure at any given point in the Earths atmosphere. ... In chemistry, a silicate is a compound containing an anion in which one or more central silicon atoms are surrounded by electronegative ligands. ... Gold is a highly ductile metal Ductility is a mechanical property which describes how much plastic deformation a material can sustain before fracture occurs. ... Convection in the most general terms refers to the movement of currents within fluids (i. ... The tectonic plates of the world were mapped in the second half of the 20th century. ... The melting point of a solid is the temperature range at which it changes state from solid to liquid. ... For other uses, see Viscosity (disambiguation). ... The pascal second (symbol PaÂ·s) is the SI unit of dynamic viscosity. ... The pascal second (symbol PaÂ·s) is the SI unit of dynamic viscosity. ... The University of Queensland pitch drop experiment, demonstrating the viscosity of bitumen. ...

Crust

The crust ranges from 5 to 70 km in depth. The thin parts are oceanic crust composed of dense (mafic) iron magnesium silicate rocks and underlie the ocean basins. The thicker crust is continental crust, which is less dense and composed of (felsic) sodium potassium aluminium silicate rocks. The crust-mantle boundary occurs as two physically different events. First, there is a discontinuity in the seismic velocity, which is known as the Mohorovičić discontinuity or Moho. The cause of the Moho is thought to be a change in rock composition from rocks containing plagioclase feldspar (above) to rocks that contain no feldspars (below). Second, there is a chemical discontinuity between ultramafic cumulates and tectonized harzburgites, which has been observed from deep parts of the oceanic crust that have been obducted into the continental crust and preserved as ophiolite sequences. Geologic provinces of the world (USGS) In geology, a crust is the outermost solid shell of a planet or moon. ... Age of oceanic crust Oceanic crust is the part of Earths lithosphere that surfaces in the ocean basins. ... In geology, mafic minerals and rocks are silicate minerals, magmas, and volcanic and intrusive igneous rocks that have relatively high concentrations of the heavier elements. ... In chemistry, a silicate is a compound containing an anion in which one or more central silicon atoms are surrounded by electronegative ligands. ... This article is about the geological substance. ... The thickness of the Earths crust (km). ... Felsic is a term used in geology to refer to silicate minerals, magmas, and rocks which are enriched in the lighter elements such as silica, oxygen, aluminium, sodium, and potassium. ... For sodium in the diet, see Salt. ... Aluminum redirects here. ... Body waves and surface waves Earthquake wave paths p-wave and s-wave from seismograph A seismic wave is a wave that travels through the Earth, most often as the result of a tectonic earthquake, sometimes from an explosion. ... Ordovician ophiolite in Gros Morne National Park, Newfoundland. ... This article does not cite any references or sources. ... For other uses, see Chemistry (disambiguation). ... Ultramafic (or ultrabasic) rocks are igneous rocks with very low silica content (less than 45%), generally >18% MgO, high FeO, low potassium and are composed of usually greater than 90% mafic minerals (dark colored, high magnesium and iron content). ... Peridotite xenolith from San Carlos, southwestern United States. ... Obduction is the overthrusting of continental crust by oceanic crust or mantle rocks. ... Ophiolites are sections of the oceanic crust and the subjacent upper mantle that have been uplifted or emplaced to be exposed within continental crustal rocks. ...

Historical development of alternative conceptions

In 1692 Edmund Halley (in a paper printed in Philosophical Transactions of Royal Society of London) put forth the idea of Earth consisting of a hollow shell about 500 miles thick, with two inner concentric shells around an innermost core, corresponding to the diameters of the planets Venus, Mars, and Mercury respectively.^[12] Halley's construct was a method of accounting for the (flawed) values of the relative density of the Earth and the Moon that had been given by Sir Isaac Newton, in Principia (1687).“Sir Isaac Newton has demonstrated the Moon to be more solid than our Earth, as 9 to 5" Halley remarked; "why may we not then suppose four ninths of our globe to be cavity?”^[12] Edmond Halley. ... This article is about Earth as a planet. ...

In 1818, John Cleves Symmes, Jr. suggested that the Earth consisted of a hollow shell about 800 miles (1,300 km) thick, with openings about 1400 miles (2,300 km) across at both poles with 4 inner shells each open at the poles. Jules Verne, in Journey to the Center of the Earth imagined vast interior caverns, and William Reed, in Phantom of the Poles (1906) imagined a hollow earth. John Cleves Symmes (1779 - May 1829) was born in New Jersey to Timothy Symmes. ... This article is about the French author. ... For other uses, see Journey to the Center of the Earth (disambiguation). ... William Reed was the author of The Phantom of the Poles, published in 1906, in which he proposed his theory that the Earth is in fact hollow, with holes at its poles. ... The Phantom of the Poles is a book written by William Reed, and published in 1906. ... A Hollow Earth theory posits that the planet Earth has a hollow interior and, possibly, a habitable inner surface. ...

Some Christian writers resisted the idea of a spherical Earth on theological grounds, without gaining widespread acceptance. The Flat Earth Society continue to oppose the concept of a spherical Earth.^[13] A rendered picture of the Flat Earth model. ...

It has been also suggested that the earth's core consists of metallic hydrogen.^[14]

See also

Ordovician ophiolite in Gros Morne National Park, Newfoundland. ... The core-mantle boundary lies between the Earths silicate mantle and its iron-nickel core. ... The Lehmann discontinuity, named after seismologist Inge Lehmann, is the boundary layer in between the liquid outer core and the solid inner core. ... Hydridic Earth theory is a hypothesis proposed in 1968 by a Soviet geologist Vladimir Larin. ... Geologic provinces of the world (USGS) In geology, a crust is the outermost solid shell of a planet or moon. ... The tectonic plates of the lithosphere on Earth. ... This article does not cite any references or sources. ... The mesosphere refers to the lower mantle in the region between the asthenosphere and the outer core. ... Earth cutaway from core to exosphere. ... Earth cutaway from core to exosphere. ... The tectonic plates of the world were mapped in the second half of the 20th century. ...

Notes

^ Spaceflight Now | Breaking News | Oldest rock shows Earth was a hospitable young planet
^ T. H. Jordan, "Structural Geology of the Earth's Interior", Proceedings of the National Academy of Science, 1979, Sept., 76(9): 4192–4200.
^ Cohen, Ronald; Stixrude, Lars. Crystal at the Center of the Earth. Retrieved on 2007-02-05.
^ Lars Stixrude and R. E. Cohen, "High-Pressure Elasticity of Iron and Anisotropy of Earth's Inner Core", Science 31 March 1995: Vol. 267. no. 5206, pp. 1972 - 1975 DOI: 10.1126/science.267.5206.1972
^ Wootton, Anne (September 2006) "Earth's Inner Fort Knox" Discover 27(9): p.18;
^ Herndon, J. M., The chemical composition of the interior shells of the Earth. Proc. R. Soc. Lond, 1980, A372, 149-154.
^ Herndon, J. M., Scientific basis of knowledge on Earth's composition. Curr.Sci., 2005, 88(7), 1034-1037.
^ Earth's Core Spins Faster Than the Rest of the Planet - New York Times
^ Kerr, Richard A. (26 August 2005) "Earth's Inner Core Is Running a Tad Faster Than the Rest of the Planet" Science 309(5739): p.1313;
^ Chang, Kenneth (26 August 2005) "Scientists Say Earth's Center Rotates Faster Than Surface" The New York Times Sec. A, Col. 1, p.13;
^ http://www2.uni-jena.de/chemie/geowiss/geodyn/poster2.html
^ ^a ^b N. Kollerstrom, 1992. "The hollow world of Edmond Halley" from Journal for History of Astronomy 23, 185-192
^ Documenting the Existence of "The International Flat Earth Society"
^ Christianson, Neil B. (1989). Earth has a cold heart. ne-do Press. ISBN 0962724009.

Year 2007 (MMVII) was a common year starting on Monday of the Gregorian calendar in the 21st century. ... is the 36th day of the year in the Gregorian calendar. ...

References

This article is about the physical universe. ... This article is about Earth as a planet. ... Geological time put in a diagram called a geological clock, showing the relative lengths of the eons of the Earths history. ... Earth science (also known as geoscience, the geosciences or the Earth Sciences), is an all-embracing term for the sciences related to the planet Earth. ... The tectonic plates of the world were mapped in the second half of the 20th century. ... Geological time scale. ... This article includes a list of works cited but its sources remain unclear because it lacks in-text citations. ... For the geological process, see Weathering or Erosion. ... Air redirects here. ... This article is about life in general. ... For other uses, see Biosphere (disambiguation). ... For the definition, see Life. ... A cluster of Escherichia coli bacteria magnified 10,000 times. ... Simplified schematic of an islands flora - all its plant species, highlighted in boxes. ... For other uses, see Plant (disambiguation). ... For the fictional character, see Fungus the Bogeyman. ... Fauna is a collective term for animal life of any particular region or time. ... For other uses, see Animal (disambiguation). ... For the song by Girls Aloud see Biology (song) Biology studies the variety of life (clockwise from top-left) E. coli, tree fern, gazelle, Goliath beetle Biology (from Greek: Î’Î¹Î¿Î»Î¿Î³Î¯Î± - Î²Î¯Î¿Ï‚, bio, life; and Î»ÏŒÎ³Î¿Ï‚, logos, speech lit. ... The evolutionary history of life and the origin of life are fields of ongoing geological and biological research. ... For other uses, see Wilderness (disambiguation). ... For the journal, see Ecology (journal). ... A coral reef near the Hawaiian islands is an example of a complex marine ecosystem. ... For other uses, see Universe (disambiguation). ... This article is about matter in physics and chemistry. ... Layers of Atmosphere - not to scale (NOAA)[1] Outer space, sometimes simply called space, refers to the relatively empty regions of the universe outside the atmospheres of celestial bodies. ...

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