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Structure of Earth. The mesosphere is labeled as Stiffer mantle in this diagram.. 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 pressure at the bottom of the mantle is ≈140 GPa (1.4 Matm). [24] The mantle is composed of silicate rocks richer in iron and magnesium than the overlying crust. [25] Although solid, the mantle's extremely hot silicate material can flow over very long timescales. [26] Convection of the mantle propels the motion of the tectonic plates in the
The internal structure of Earth. Earth's mantle is a layer of silicate rock between the crust and the outer core.It has a mass of 4.01 × 10 24 kg (8.84 × 10 24 lb) and makes up 67% of the mass of Earth. [1]
While it seems to be generated mostly by fluid and electric currents in the outer core, those currents are strongly affected by the presence of the solid inner core and by the heat that flows out of it. (Although made of iron, the core is not ferromagnetic, due to being above the Curie temperature.) [citation needed]
Mantle convection is the result of a thermal gradient: the lower mantle is hotter than the upper mantle, and is therefore less dense. This sets up two primary types of instabilities. In the first type, plumes rise from the lower mantle, and corresponding unstable regions of lithosphere drip back into the mantle.
The remaining heat flow at the surface would be due to basal heating of the crust from mantle convection. Heat fluxes are negatively correlated with rock age, [1] with the highest heat fluxes from the youngest rock at mid-ocean ridge spreading centers (zones of mantle upwelling), as observed in the global map of Earth heat flow. [1]
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]
Recently it has been proposed that a higher core cooling rate and lower mantle cooling rate can resolve the paradox in part. [6] [7] [8] However, the paradox remains unresolved. Also, recent geochemical experiments [9] have led to the proposal that radiogenic heat in the core is larger than previously thought. This revision, if true, would also ...