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Asthenosphere

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	Asthenosphere
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	Topics Asthenosphere Topic Home The asthenosphere (from an invented GreekGreek language Greek has a documented history of 3,500 years, the longest of any single language within the Indo-European family.... a + 'sthenos "without strength" and greek word sfa??a (sphera) meaning globe) is the region of the EarthFacts About Earth Earth is the third planet in the solar system in terms of distance from the Sun, and the fifth largest.... between 100 and 200 kmMetre The metre, or meter , is a measure of length.... (~ 62 and 124 milesMile A mile is the name of a unit of length, usually used to measure distance, in a number of different systems, including Englis... ) below the surface — but perhaps extending as deep as 400 km (~ 249 miles) — that is the weak or "soft" zone in the upper mantleMantle (geology) Earth's mantle is the thick shell of dense rock surrounding the liquid metallic Earth's outer core, and lies directly beneat... . It lies just below the lithosphereLithosphere The lithosphere is the solid outermost shell of a rocky planet.... , which is involved in plate movementsPlate tectonics Plate tectonics is a theory of geology developed to explain the observed evidence for large scale motions within the Earth'... and isostaticIsostasy Isostasy is a term used in Geology to refer to the state of gravitational equilibrium between the Earth's lithosphere and as... adjustments. In spite of its heat, pressures keep it plasticPlasticity (physics) In physics and materials science, plasticity is a property of a material to undergo a non-reversible change of shape in res... , and it has a relatively low density. SeismicSeismology Seismology is the scientific study of earthquakes and the movement of waves through the Earth.... waves, the speed of which decrease with decreasing rigidityRigidity Generally, rigidity refers to inflexibility or resistance to change.... of a medium, pass relatively slowly through the asthenosphere, the cue that originally alerted seismologistsSeismology Seismology is the scientific study of earthquakes and the movement of waves through the Earth.... to its presence; thus it has been given the name low-velocity zone. Under the thin oceanic plates the asthenosphere is usually much nearer the seafloor surface, and at mid-ocean ridgeMid-ocean ridge A mid-ocean ridge or mid-oceanic ridge is an underwater mountain range, formed by plate tectonics.... s it rises to within a few kilometres of the ocean floor. The upper part of the asthenosphere is believed to be the zone upon which the great rigid and brittle lithospheric plates of the Earth's crust move about. Due to the temperatureFacts About Temperature In thermodynamics, temperature is a measure of the tendency of an object or system to spontaneously give up energy.... and pressurePressure Overview Pressure is the force per unit area applied on a surface in a direction perpendicular to that surface.... conditions in the asthenosphere, rockRock (geology) A rock is a naturally occurring aggregate of minerals and/or mineraloids.... becomes ductile, moving at rates of deformation measured in cm/yr over lineal distances eventually measuring thousands of kilometers. In this way, it flows like a convectionConvection Summary Convection is the transfer of potential energy, for example heat, by currents within liquids and gases.... current, radiating heat outward from the Earth's interior. Above the asthenosphere, at the same rate of deformation, rock behaves elastically and, being brittle, can break, causing faultsGeologic fault Overview Geologic faults or simply faults are planar rock fractures, which show evidence of relative movement.... . The rigid lithosphere is thought to "float" or move about on the slowly flowing asthenosphere, creating the movement of crustal plates described by Plate tectonicsPlate tectonics Plate tectonics is a theory of geology developed to explain the observed evidence for large scale motions within the Earth'... theory. Although its presence was suspected as early as 1926, the worldwide occurrence of the asthenosphere was confirmed by analyses of earthquakeEarthquake An earthquake is a phenomenon that results from and is powered by the sudden release of stored energy that radiates seismic ... waves from the Great Chilean EarthquakeGreat Chilean Earthquake The Great Chilean Earthquake or Valdivia Earthquake of May 22, 1960 is the largest magnitude earthquake recorded sinc... of May 22, 1960. External links