“asthenosphere”的概念、定义、翻译、参考文献-科学参考

asthenosphere

Physics

A layer of the earth’s mantle (see earth) that underlies the lithosphere at a depth of about 70 km. The velocity of seismic waves is considerably reduced in the asthenosphere and it is thought to be a zone of partial melting. It extends to a depth of about 250 km where rocks are solid.

Astronomy

A weak layer within a planetary body, beneath the rigid outer layer known as the lithosphere. It is slightly weaker than the lithosphere and deformable over long periods, allowing continental drift to take place on the Earth. On other planets and satellites the asthenosphere allows the topography to smooth out slowly, highlands becoming lower and deep basins shallower. The depth of the asthenosphere varies according to the size, density, composition, and thermal structure of the planet or satellite. On Earth, the top of the asthenosphere is around 100 km below the surface, but on the Moon it lies 800 km below the surface, more than half-way to the centre.

Biology

See plate tectonics.

Geology and Earth Sciences

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).

Geography

That zone of the Earth’s mantle which lies beneath the relatively rigid lithosphere, between 50 and 300 km below the surface, and representing a mechanical boundary between more rigid regions above and below. It is approximately commensurate with that zone of the mantle which transmits seismic waves at low velocity. The asthenosphere represents the location in the mantle where the melting point is most closely approached, and the transition between a rigid lithosphere and a viscous asthenosphere is gradational (Stüwe (1999) Surveys Geophys. 20). The asthenosphere is composed of hot, semi-molten, and therefore deformable, rock, and may be plate- or density-driven, or both (Hansen et al. (2006) Geology 34, 10).

单词	asthenosphere
释义	asthenosphere Physics A layer of the earth’s mantle (see earth) that underlies the lithosphere at a depth of about 70 km. The velocity of seismic waves is considerably reduced in the asthenosphere and it is thought to be a zone of partial melting. It extends to a depth of about 250 km where rocks are solid. Astronomy A weak layer within a planetary body, beneath the rigid outer layer known as the lithosphere. It is slightly weaker than the lithosphere and deformable over long periods, allowing continental drift to take place on the Earth. On other planets and satellites the asthenosphere allows the topography to smooth out slowly, highlands becoming lower and deep basins shallower. The depth of the asthenosphere varies according to the size, density, composition, and thermal structure of the planet or satellite. On Earth, the top of the asthenosphere is around 100 km below the surface, but on the Moon it lies 800 km below the surface, more than half-way to the centre. Biology See plate tectonics. Geology and Earth Sciences 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). Geography That zone of the Earth’s mantle which lies beneath the relatively rigid lithosphere, between 50 and 300 km below the surface, and representing a mechanical boundary between more rigid regions above and below. It is approximately commensurate with that zone of the mantle which transmits seismic waves at low velocity. The asthenosphere represents the location in the mantle where the melting point is most closely approached, and the transition between a rigid lithosphere and a viscous asthenosphere is gradational (Stüwe (1999) Surveys Geophys. 20). The asthenosphere is composed of hot, semi-molten, and therefore deformable, rock, and may be plate- or density-driven, or both (Hansen et al. (2006) Geology 34, 10).
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