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A mantle plume is a proposed mechanism of convection within the Earth's mantle, hypothesized to explain anomalous volcanism. [2] 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.
The volcanism is caused by the African Plate moving slowly over a hotspot in the Earth's mantle. A hotspot (the Canary hotspot) is the explanation accepted by most geologists who study the Canary Islands. [33] [34] A relatively hot mantle plume associated with this hotspot is thought to be rising through the mantle under La Palma and El Hierro ...
There is an ongoing discussion about whether the hotspot is caused by a deep mantle plume or originates at a much shallower depth. [3] Recently, seismic tomography studies have found seismic wave speed anomalies under Iceland, consistent with a hot conduit 100 km (62 mi) across that extends to the lower mantle.
Hot mantle materials rising up in a plume can spread out radially beneath the tectonic plate causing regions of uplift. [13] These ascending plumes play an important role in LIP formation. When created, LIPs often have an areal extent of a few million square kilometers and volumes on the order of 1 million cubic kilometers.
The volcanism often attributed to deep mantle plumes is alternatively explained by passive extension of the crust, permitting magma to leak to the surface: the plate hypothesis. [ 24 ] The convection of the Earth's mantle is a chaotic process (in the sense of fluid dynamics ), which is thought to be an integral part of the motion of plates.
This is widely believed to have been supplied by a mantle plume impinging on the base of the Earth's lithosphere, its rigid outermost shell. [29] [30] [15] The plume consists of unusually hot mantle rock of the asthenosphere, the ductile layer just below the lithosphere, that creeps upwards from deeper in the Earth's interior. [31]
Mantle plumes were first proposed by J. Tuzo Wilson in 1963 [4] [non-primary source needed] and further developed by W. Jason Morgan in 1971. A mantle plume is posited to exist where hot rock nucleates [clarification needed] at the core-mantle boundary and rises through the Earth's mantle becoming a diapir in the Earth's crust. [5]
Second, flow of hot mantle material encounters the base of the thin lithosphere and often results in melting and a new phase of volcanism. Delamination may thus account for some volcanic regions that have been attributed to mantle plumes in the past. [6]