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Numerical models of mantle convection in which the viscosity is dependent both on temperature and strain rate reliably produce an oceanic asthenosphere, suggesting that strain-rate weakening is a significant contributing mechanism, [24] and explaining the particularly weak asthenosphere below the Pacific plate.
The lithosphere consists of the crust and upper solid mantle (lithospheric mantle). The green dashed line marks the LAB. The green dashed line marks the LAB. The lithosphere–asthenosphere boundary (referred to as the LAB by geophysicists) represents a mechanical difference between layers in Earth's inner structure .
Diagram of a cross-section of the Patagonia slab window. The Nazca plate and Antarctic plate are colliding with the South American plate at the Chile Ridge. [1]In geology, a slab window is a gap that forms in a subducted oceanic plate when a mid-ocean ridge meets with a subduction zone and plate divergence at the ridge and convergence at the subduction zone continue, causing the ridge to be ...
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 ...
The presence of hot asthenospheric mantle at shallow levels beneath the western margin of North America is likely to generate melt and cause magmatism. Accordingly, a sequence of volcanoes in the wake of the MTJ passing were activated; this magmatism likely leads to the intrusion of plutons within the overlying crust in the region.
Far field stresses thin the crust and lithospheric mantle, and hot asthenospheric mantle passively enters the thinned area. [10] The upwelling of asthenosphere is not involved in the actual rifting process. The upward flow of the asthenosphere results in decompression melting, magmatic underplating and some volcanism that may occur in the rift ...
The slab gap hypothesis proposes that instead of a "window", the descending slab leaves behind a "gap" through which the asthenospheric mantle of the former spreading zone continues to act beneath the overriding plate. This hypothesis then assumes that a crustal spreading zone is also underpinned by a corresponding asthenospheric mantle ...
In geology, plating is a hypothesized process whereby asthenospheric mantle hardens beneath crustal material, thereby becoming attached to it and thereafter moving together with the crustal material as part of the lithosphere. [1] A complementary process, although it does not necessarily always involve the upper mantle, is called delamination.