Mantle Plume

A mantle plume is a posited thermal abnormality where hot rock nucleates at the core-mantle boundary and rises through the Earth's mantle becoming a diapir in the Earth's crust. Such plumes were invoked in 1971 to explain volcanic regions that were not thought to be explicable by the then-new theory of plate tectonics. Some of these volcanoes lie far from tectonic plate boundaries, e.g., Hawaii. Others represent unusually large-volume volcanism whether on plate boundaries, e.g., Iceland or basalt floods like the Deccan or Siberian traps. The currently active volcanic centers are known as "hot spots". In particular, the concept that mantle plumes are fixed relative to one another, and anchored at the core-mantle boundary, was thought to provide a natural explanation for the time-progressive chains of older volcanoes seen extending out from some "hot spots".

The hypothesis of mantle plumes is not universally accepted. Many of its predictions have not been confirmed by observation. As a result, it has required progressive hypothesis-elaboration, and many variant types have been proposed such as mini-plumes and pulsing plumes. Another hypothesis for unusual volcanic regions is the "Plate model". This attributes volcanoes to passive leakage of magma from the mantle onto the Earth's surface where extension of the lithosphere permits it. This model attributes essentially all volcanism to plate tectonic processes, with volcanoes far from plate boundaries resulting from intraplate extension.