Notion of dynamics
	Gravitational force & 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