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The lower mantle, historically also known as the mesosphere, represents approximately 56% of Earth's total volume, and is the region from 660 to 2900 km below Earth's surface; between the transition zone and the outer core. [1]
The lower mantle is composed primarily of bridgmanite and ferropericlase, with minor amounts of calcium perovskite, calcium-ferrite structured oxide, and stishovite ...
The mantle is divided into upper and lower mantle [21] separated by a transition zone. [22] 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 GPa (1.4 Matm). [24]
Tectonic plates slide very slowly over the Earth's mantle, a lower place of rock that is heated from the Earth's interior. Several huge sections of the Earth's crust are impelled by heat currents in the mantle, producing tremendous forces that can buckle the material at the edges of the plates to form mountains. Usually one plate is forced ...
The transition zone is the part of Earth's mantle that is located between the lower and the upper mantle, most strictly between the seismic-discontinuity depths of about 410 to 660 kilometres (250 to 410 mi), but more broadly defined as the zone encompassing those discontinuities, i.e., between about 300 and 850 kilometres (190 and 530 mi) depth. [1]
An approximately 200 km thick layer of the lower mantle directly above the CMB is referred to as the D″ region ("D double-prime" or "D prime prime") and is sometimes included in discussions regarding the core–mantle boundary zone. [3] The D″ name originates from geophysicist Keith Bullen's designations for the Earth's layers.
Simplified model of mantle convection: [1] Whole-mantle convection. Mantle convection is the very slow creep of Earth's solid silicate mantle as convection currents carry heat from the interior to the planet's surface. [2] [3] Mantle convection causes tectonic plates to move around the Earth's surface. [4]
The existence of silicate perovskite in the mantle was first suggested in 1962, and both MgSiO 3 and CaSiO 3 had been synthesized experimentally before 1975. By the late 1970s, it had been proposed that the seismic discontinuity at about 660 km in the mantle represented a change from spinel structure minerals with an olivine composition to silicate perovskite with ferropericlase.