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GPE and Convective Thinning
Convective thinning describes the drag, into the convective mantle, of the lower part of the lithospheric mantle. This mechanism corresponds to the development of a Rayleigh-Taylor gravitational instability (driven by a density inversion): The heavy yet weak lower part of the lithospheric mantle is gravitationaly instable with respect to its surrounding.
Depending on the rheology of the lithospheric mantle Houseman and Molnar (1997) estimated that the part comprised in between the isotherm 900±100º and the isotherm 1300º is gravitationally unstable. The detachment of this heavy keel from the rest of the lithosphere dramatically changes the balance of forces. Convective thinning results in a sudden increase in GPE stored in the thickened crust, and therefore promotes extensional collapse.
Animation © Schmeling |
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