Mantle Plume Hypothesis

The mantle plume hypothesis proposes that some volcanic activity on Earth's surface, particularly volcanism occurring away from the boundaries between tectonic plates, is caused by narrow columns of unusually hot rock, called mantle plumes, rising from deep within the Earth's mantle, possibly originating as deep as the boundary between the mantle and the planet's core, rather than being directly caused by plate tectonic processes at shallower depth. Geophysicist W. Jason Morgan proposed the hypothesis in a 1971 paper, developing it specifically to explain hotspot volcanism, chains of volcanic islands and seamounts, such as the Hawaiian island chain, that form as a tectonic plate moves steadily over what Morgan proposed was a comparatively fixed, deep-seated source of rising heat. Under the hypothesis, as an oceanic plate drifts across a stationary mantle plume over millions of years, it produces a linear trail of progressively older extinct volcanoes trailing away from the currently active one sitting directly above the plume. While a broadly accepted explanation for several major hotspot chains, the mantle plume hypothesis has remained a genuinely debated topic within geophysics, since the existence, depth of origin, and even fixed positioning of specific proposed plumes have proven difficult to establish conclusively using seismic imaging techniques, with some researchers proposing alternative explanations for certain hotspots.