Deep Mantle Convection Plumes and Plate Motions

TLDR

Volcanic island chains and aseismic ridges form from plate motion over fixed‑mantle hotspots, which are thought to be surface expressions of deep mantle plumes about 150 km wide rising at ~2 m yr⁻¹ to the mantle’s base, linking hotspots to continental drift. The rising plume material spreads laterally in the asthenosphere, generating stresses on the underlying plates. Order‑of‑magnitude estimates indicate these stresses are large enough to significantly influence plate motion, with total plume upward flow of ~500 cu km yr⁻¹ implying a mantle overturn every ~2 billion years.

Abstract

Evidence shows that volcanic island chains and aseismic ridges are formed by plate motion over fixed-mantle (Iceland, Hawaii, Galapagos, etc.) and new arguments link these hot-spots with the driving mechanism of continental drift. It is assumed that the hot-spots are surface expressions of deep mantle plumes roughly 150 km in diameter, rising 2 m/year, and extending to the lowest part of the mantle. The rising material spreads out in the asthenosphere, producing stresses on the plate bottoms. Order-of-magnitude estimates show these stresses are sufficiently large to influence plate motion significantly. the total upward flow in the plumes is estimated at 500 cu km/year, which would require the entire mantle to overturn once each 2 billion years.