Mechanisms of Active and Passive Rifting

Turcotte, D.L. and Emerman, S.H., 1983. Mechanisms of active and passive rifting. In: P. Morgan and B.H. Baker (Editors), Processes of Continental Rifting. Tectonophysics, 94: 39–50. In this paper we obtain two solutions relating to the alternative active and passive hypotheses for continental rifting. Active rifting assumes the impingement of a mantle plume on the base of the continental lithosphere. We determine the rate of lithosphere thinning due to this impingement. We conclude that it takes 50–75 million years to thin the continental lithosphere to the base of the crust; the long length of time required appears to rule out this lithospheric erosion mechanism as a viable mechanism for complete lithospheric thinning. We suggest that diapiric penetration is the mechanism by which hot mantle rock reaches the base of the continental crust at a rift. We have also obtained values for the tensional stresses generated by the diapiric penetration of hot asthenospheric rock into the lithosphere. The stress levels are obtained as functions of lithospheric and crustal thinning factors. These stresses may lead to rift propagation and the splitting of a continent.