Question

1) what do you understand by mantle plumes. Discuss. Also, explain their importance in earth sciences.(250 words)

Answer 1

Convection in the mantle transports heat from the core to the Earth’s surface in thermal diapirs. Two largely independent convective processes occur in the mantle: the broad convective flow associated with plate tectonics, which is driven primarily by the sinking of cold plates of lithosphere back into the mantle asthenosphere, and mantle plumes, which carry heat upward in narrow, rising columns, driven by heat exchange across the core-mantle boundary. The latter type of convection is postulated to be independent of plate motions.A mantle plume is posited to exist where hot rock nucleates at the core-mantle boundary and rises through the Earth’s mantle becoming a diapir in the Earth’s crust. The currently active volcanic centers are known as hotspots. 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 hot spots, such as the Hawaiian–Emperor seamount chain.

The narrow vertical pipe, or conduit, postulated to connect the plume head to the core-mantle boundary, is viewed as providing a continuous supply of magma to a fixed location, often referred to as a “hotspot”. As the overlying tectonic plate (lithosphere) moves over this hotspot, the eruption of magma from the fixed conduit onto the surface is expected to form a chain of volcanoes that parallels plate motion. These mantle are 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 or in large igneous provinces etc.

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