Summary
A mantle plume is a proposed mechanism of convection within the Earth's mantle, hypothesized to explain anomalous volcanism. Because the plume head partially melts on reaching shallow depths, a plume is often invoked as the cause of volcanic hotspots, such as Hawaii or Iceland, and large igneous provinces such as the Deccan and Siberian Traps. Some such volcanic regions lie far from tectonic plate boundaries, while others represent unusually large-volume volcanism near plate boundaries. Mantle plumes were first proposed by J. Tuzo Wilson in 1963 and further developed by W. Jason Morgan in 1971 and 1972. A mantle plume is posited to exist where super-heated material forms (nucleates) at the core-mantle boundary and rises through the Earth's mantle. Rather than a continuous stream, plumes should be viewed as a series of hot bubbles of material. Reaching the brittle upper Earth's crust they form diapirs. These diapirs are "hotspots" in the crust. In particular, the concept that mantle plumes are fixed relative to one another and anchored at the core-mantle boundary would provide a natural explanation for the time-progressive chains of older volcanoes seen extending out from some such hotspots, for example, the Hawaiian–Emperor seamount chain. However, paleomagnetic data show that mantle plumes can also be associated with Large Low Shear Velocity Provinces (LLSVPs) and do move relative to each other. The current mantle plume theory is that material and energy from Earth's interior are exchanged with the surface crust in two distinct and largely independent convective flows: as previously theorized and widely accepted, the predominant, steady state plate tectonic regime driven by upper mantle convection, mainly the sinking of cold plates of lithosphere back into the asthenosphere. the punctuated, intermittently dominant mantle overturn regime driven by plume convection that carries heat upward from the core-mantle boundary in a narrow column. This second regime, while often discontinuous, is periodically significant in mountain building and continental breakup.
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