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asthenosphere
asthenosphere
asthenosphere The weak zone within the upper
mantle, underlying the
lithosphere, where the mantle rocks deform by plastic flow in response to applied stresses of the order of 100 MPa. It is commonly considered to be coincident with the upper-mantle seismic
low-velocity zone, but this is probably valid only for the oceanic sectors of the mantle. Viscosity is of the order of 10
21–22 poise, i.e. the same as the underlying mantle, but it is much more ‘fluid’ than the overlying lithosphere. Originally it was recognized as a possible explanation for
isostatic behaviour, and it is generally recognized as a mantle zone within which convective motions take place. The depth of
earthquake foci in
subduction zones suggests that descending convection limbs penetrate to 700 km, just above the upper mantle–lower mantle boundary. Rising limbs of asthenospheric mantle convection are located under surface spreading centres (
mid-oceanic ridges).
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Continental roots go deep, but not as deep as some thought.
Newspaper article from: Science Letter; 5/12/2003; 700+ words
; ...ocean basins, and under that is the asthenosphere - the very top of the mantle," said...slow down when they pass through the asthenosphere. The UC Berkeley team argues that...seismic shear waves slow down in the asthenosphere, while the horizontally polarized...
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Research on geophysics published by scientists at Columbia University.
Newspaper article from: Physics Week; 11/3/2009; 700+ words
; ...show that dynamic thinning of asthenosphere can explain the magnitude and...describe flow of thin viscous asthenosphere were linearized. At the EPR, fast plate divergence thins the asthenosphere by both sequestering it into diverging...
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Research results from Lomonosov Moscow State University update understanding of earth sciences.
Newspaper article from: Electronics Newsweekly; 9/10/2008; 700+ words
; ...reflecting the topography of the conducting asthenosphere arise via the galvanic channel, which...concentrates in uplifts of the conducting asthenosphere), which is inactive in the case of...below into uplifts of the conducting asthenosphere), which is free from the screening...
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Study data from University of Tokyo provide new insights into science.
Newspaper article from: Science Letter; 5/19/2009; 700+ words
; ...mobility of the lithosphere over a weaker asthenosphere constitutes the essential element of...the processes at the lithosphere-asthenosphere boundary (LAB) is fundamental to...the LAB requires a partially molten asthenosphere consisting of horizontal melt-rich...
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VOLCANIC ACTIVITY BENEATH PACIFIC OCEAN MAY INDICATE EARTH'S UPPER MANTLE IS MORE 'LIQUEFIED' THAN PREVIOUSLY THOUGHT
News Wire article from: US Fed News Service, Including US State News; 7/27/2006; 700+ words
; ...around the Earth on top of the ductile asthenosphere, the top of the convecting portion...pre-existing melt from Earth's asthenosphere as the plate flexes and fractures when...The presence of partial melt in the asthenosphere remains controversial. "Many of the...
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The coastal flexure of Disko (West Greenland), onshore expression of the 'obliqe reflectors'
Magazine article from: Journal of the Geological Society; 5/1/1998; ; 700+ words
; ...adiabatic decompression of the underlying asthenosphere. This decompression would be enhanced...secondary convection of the underlying asthenosphere of normal temperature (Anderson 1993...potential temperature anomaly of the asthenosphere ranging between 100 and 200 deg C above...
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August 2009 Lithosphere media highlights.
Newspaper article from: NewsRx Health & Science; 8/23/2009; 700+ words
; ...mountain belts?" Subducted oceanic asthenosphere and upper mantle flow beneath the Juan...are underlain by a weak layer -- the asthenosphere -- characterized by slow seismic velocities...km depth, but what happens to this asthenosphere when the oceanic plate above it subducts...
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Continental roots might not be as deep as suspected
Magazine article from: Sea Technology; 5/1/2003; ; 581 words
; ...ocean basins, and under that is the asthenosphere-the very top of the mantle," said...slow down when they pass through the asthenosphere. The UC Berkeley team argues that...seismic shear waves slow down in the asthenosphere, while the horizontally polarized...
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Volcanoes: they're the most powerful expressions of nature's might, responsible for mass extinctions, global climate change and the demise of entire civilisations, but how much do we really know about volcanoes? And just how close are we to the Holy Grail of accurately predicting when they're going to explode?(SPECIAL REPORT: Geographical dossier)(Cover story)
Magazine article from: Geographical; 3/1/2007; ; 700+ words
; ...plates exposes the hot rock of the asthenosphere, the upper layer of the mantle. As...where an oceanic plate sinks into the asthenosphere below either another oceanic plate...oceanic plate descends into the hot asthenosphere, heat and pressure melt the minerals...
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Research on geophysics detailed by scientists at Indiana University.
Newspaper article from: Physics Week; 3/31/2009; 700+ words
; ...and distributed viscous flow in the asthenosphere," scientists writing in the Geophysical...overlying a linear, Maxwell, viscoelastic asthenosphere. We devise a scheme to simultaneously...parameters, lithosphere thickness and asthenosphere viscosity. The postseismic GPS time...
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Asthenosphere
Encyclopedia entry from: The Gale Encyclopedia of Science
Asthenosphere The asthenosphere is the ductile layer situated beneath Earth ’ s rigid...the lithosphere, or outer layer of rock-like material; the asthenosphere; and the centrosphere, or central part of the planet. The...
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asthenosphere
Book article from: A Dictionary of Astronomy
asthenosphere A weak layer within a planetary body...On other planets and satellites the asthenosphere allows the topography to smooth out...basins shallower. The depth of the asthenosphere varies according to the size, density...
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Earth's Interior
Encyclopedia entry from: UXL Encyclopedia of Science
...potassium, and oxygen. Words to Know Asthenosphere: Portion of the mantle beneath the...the lithosphere and the underlying asthenosphere. Lithosphere: Rigid uppermost section...This "soft" zone is called the asthenosphere, from the Greek word asthenes, meaning...
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Plate Tectonics
Book article from: Water:Science and Issues
...mechanical layers — the lithosphere and asthenosphere. The lithosphere is the outermost of these...narrow, mobile zone of the mantle called the asthenosphere. The asthenosphere is a weak zone, formed of mostly solid rock...
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Europe
Encyclopedia entry from: The Gale Encyclopedia of Science
...x201D; Below the lithosphere is the asthenosphere , where solid rock stretches and flows...called plates, and floats on top of the asthenosphere, because it is less dense than the asthenosphere. The motion of a tireless heat engine...
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