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On Earth, the Rayleigh number for convection within Earth's mantle is estimated to be of order 10 7, which indicates vigorous convection. This value corresponds to whole mantle convection (i.e. convection extending from the Earth's surface to the border with the core). On a global scale, surface expression of this convection is the tectonic ...
This color schlieren image reveals thermal convection from a human hand (in silhouette form) to the surrounding still atmosphere. Two types of convective heat transfer may be distinguished: Free or natural convection : when fluid motion is caused by buoyancy forces that result from the density variations due to variations of thermal ± ...
Convection within Earth's mantle is the driving force for plate tectonics. 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.
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 volcanism often attributed to deep mantle plumes is alternatively explained by passive extension of the crust, permitting magma to leak to the surface: the plate hypothesis. [24] The convection of the Earth's mantle is a chaotic process (in the sense of fluid dynamics), which is
Directly above the core–mantle boundary is a 200-kilometer (120 mi) thick layer of the lower mantle. This layer is known as the D″ ("D double-prime" or "D prime prime") or degree two structure. [6] LLSVPs were discovered in full mantle seismic tomographic models of shear velocity as slow features at the D″ layer beneath Africa and the ...
A process previously proposed to contribute to plate motion and the formation of new oceanic crust at mid-ocean ridges is the "mantle conveyor" due to deep convection (see image). [27] [28] However, some studies have shown that the upper mantle (asthenosphere) is too plastic (flexible) to generate enough friction to pull the tectonic plate along.
Iceland is the type example of a volcanic anomaly situated on a plate boundary. Yellowstone, together with the Eastern Snake River Plain to its west, is the type example of an intra-continental volcanic anomaly. Hawaii, along with the related Hawaiian-Emperor seamount chain, is the type example of an intra-oceanic volcanic anomaly. [7]