Search results
Results From The WOW.Com Content Network
The lithosphere–asthenosphere boundary (referred to as the LAB by geophysicists) represents a mechanical difference between layers in Earth's inner structure. Earth's inner structure can be described both chemically ( crust , mantle , and core ) and mechanically.
The lowest part of the mantle next to the core-mantle boundary is known as the D″ (D-double-prime) layer. [23] The pressure at the bottom of the mantle is ≈140 G Pa (1.4 M atm ). [ 24 ] The mantle is composed of silicate rocks richer in iron and magnesium than the overlying crust. [ 25 ]
Interaction of the asthenosphere, lithosphere, and surface though the mantle process of subduction at an oceanic-continental plate boundary. Volcanism which originates from the mantle occurs on the surface. Interaction of the asthenosphere, lithosphere, and surface through the mantle process of slab break-off. Grey indicates crust, purple ...
The tectonic plates of the lithosphere on Earth Earth cutaway from center to surface, the lithosphere comprising the crust and lithospheric mantle (detail not to scale). A lithosphere (from Ancient Greek λίθος (líthos) 'rocky' and σφαίρα (sphaíra) 'sphere') is the rigid, [1] outermost rocky shell of a terrestrial planet or natural satellite.
The crust and the cold, rigid, top of the upper mantle are collectively known as the lithosphere, which is divided into independently moving tectonic plates. [131] Beneath the lithosphere is the asthenosphere, a relatively low-viscosity layer on which the lithosphere rides.
Lithosphere underlying ocean crust has a thickness of around 100 km (62 mi), whereas lithosphere underlying continental crust generally has a thickness of 150–200 km (93–124 mi). [5] The lithosphere and overlying crust make up tectonic plates, which move over the asthenosphere. Below the asthenosphere, the mantle is again relatively rigid.
The velocity of the S waves in the core varies smoothly from about 3.7 km/s at the center to about 3.5 km/s at the surface. That is considerably less than the velocity of S waves in the lower crust (about 4.5 km/s) and less than half the velocity in the deep mantle, just above the outer core (about 7.3 km/s). [5]: fig.2
The upwelling asthenosphere forms two chilled, solid boundary layers on the top and bottom of the sill layer. This reduces the thickness of the portion of the lowermost crust which behaves viscously. Subsidence of the lithosphere acts to increase the thickness of the portion of the lowermost crust which behaves viscously.