General Features of Mantle Plumes

A mantle plume is generally considered to be a blob of relatively hot, low-density mantle that rises because of its buoyancy. The existence of mantle plumes in the Earth was first suggested by J. Tuzo Wilson (1963) as an explanation of oceanic island chains, such as the Hawaiian–Emperor chain, that change progressively in age along the chain. Wilson proposed that as a lithospheric plate moves across a fixed hotspot (the mantle plume), volcanism is recorded as a linear array of volcanic seamounts and islands parallel to the direction in which the plate is moving. Morgan (1971) championed the idea of mantle plumes, suggesting that flood basalts formed by melting of plume heads, whereas hotspot volcanic chains were derived from partial melting of plume tails. He also showed that closely spaced hotspots on the same plate had not moved significantly relative to each other and suggested this was evidence that the plumes had come from the core–mantle boundary (Morgan 1972). Morgan noted that some hotspot tracks, like the Mascarene–Chagos–Laccadive track in the Indian Ocean, are traceable to flood basalts and can be used to reconstruct paths of opening ocean basins. Richards, Duncan, and Courtillot (1989) recognized at least 10 flood basalt–hotspot track pairs that formed from mantle plumes in the last 250 Myr.

The first laboratory experiments aimed at understanding mantle plumes better were those of Whitehead and Luther (1975), who showed that plume viscosity has an important effect on the shape of a plume.