CONTINENTAL BREAKUP
Dynamic aspects of continental breakup: Why do continents break ? :
Active vs Passive Rifting ...
Active rifting => Gravitational forces: Mantle upwelling and decompression trigger lithospheric extension. In the active rifting dynamic mode, volcanism precedes the onset of extensional deformation, as mantle upwelling triggers horizontal extension. A large doming of the crust (dynamic topography supported by mantle upwelling) with erosion precedes also extension. Active rifting can result from the drag into the convective mantle of the cold sub-orogenic mantle keel.