STARTING PLUMES AND CONTINENTAL BREAK-UP

Laboratory studies of fluid dynamic analogs of mantle plumes have led to important advances in our understanding of the life cycle of hotspots. Melting within the large volume heads of starting plumes gives rise to flood basalt provinces, while uplift of the surface above plumes results in horizontal deviatoric stresses that may precipitate considerable continental extension. However, for modern-day plumes the magnitude of these stresses appears incapable of actually initiating true continental break-up; rather, the rise of a new plume may lead to the local reorganisation of plate-scale motions (including ridge jumping), enhanced propagation of an existing ridge system, or provide sufficient extra force to drive a weak plate-scale system from slow spreading through to continental rifting. Thus, although plumes do not provide the ultimate driving force for continental break-up (these come from the plate-scale motions), the extra gravitational potential that they impose means that they play an important role in determining both where and when continental break-up does occur.