Dripping or delamination? A range of mechanisms for removing the lower crust or lithosphere

Abstract

Under some conditions, dense parts of the lower crust or mantle lithosphere can become unstable, deform internally and sink into the less dense, underlying asthenosphere. Two endmember mechanisms for this process are delamination and dripping. Numerical calculations are used to compare the time taken for each instability to grow from initiation to the point of rapid descent through the asthenosphere. This growth period is an order of magnitude shorter for delamination than dripping. For delamination, the growth rate varies proportionally to the buoyancy and viscosity of the sinking material, as with dripping. It also depends on the relative thickness (L'c) and viscosity (η ' c) of the weak l..