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The asthenosphere is a part of the upper mantle just below the lithosphere that is involved in plate tectonic movement and isostatic adjustments. It is composed of peridotite, a rock containing mostly the minerals olivine and pyroxene. [2] The lithosphere-asthenosphere boundary is conventionally taken at the 1,300 °C (2,370 °F) isotherm.
The lithosphere–asthenosphere boundary lies between Earth's cooler, rigid lithosphere and the warmer, ductile asthenosphere. The actual depth of the boundary is still a topic of debate and study, although it is known to vary according to the environment. [1]
Asthenosphere – Highly viscous, ductile, and mechanically weak region of Earth's mantle; Continent – Large geographical region identified by convention; Craton – Old and stable part of the continental lithosphere Platform – A continental area covered by relatively flat or gently tilted, mainly sedimentary strata
Plate tectonics (from Latin tectonicus, from Ancient Greek τεκτονικός (tektonikós) 'pertaining to building') [1] is the scientific theory that Earth's lithosphere comprises a number of large tectonic plates, which have been slowly moving since 3–4 billion years ago.
Mechanically, it can be divided into lithosphere, asthenosphere, mesospheric mantle, outer core, and the inner core. Chemically, Earth can be divided into the crust, upper mantle, lower mantle, outer core, and inner core. [6] The geologic component layers of Earth are at increasing depths below the surface. [6]: 146
asthenosphere A region of the Earth's outer shell beneath the lithosphere. The asthenosphere is of indeterminate thickness and behaves plastically. augite A complex aluminous silicate of calcium, iron and magnesium, crystallising in the monoclinic system, and occurring in many igneous rocks, particularly those of basic composition.
Below the asthenosphere, the mantle is again relatively rigid. The Earth's mantle is divided into three major layers defined by sudden changes in seismic velocity: [ 6 ] the upper mantle (starting at the Moho, or base of the crust around 7 to 35 km [4.3 to 21.7 mi] downward to 410 km [250 mi]) [ 7 ]
As delamination continues, more asthenosphere rises to replace the lower lithosphere as it sinks. This process causes three different changes to occur which can have an effect on the delamination process. [1] If the viscosity of the upwelling asthenosphere is greater than that of the mantle lithosphere, delamination will stop.