A mantle plume is a localized buoyant upwelling in a planetary mantle. Hot material can rise because thermal expansion lowers its density relative to its surroundings; compositional differences may strengthen or oppose that buoyancy. As it rises and decompresses, it can cross a rock's solidus and produce melt without requiring heat to be added during ascent.
A volcanic chain, a broad topographic swell or a seismic anomaly can motivate a plume interpretation, but they measure different consequences. Plate motion, background mantle flow, melt transport and crustal structure influence the surface expression. A plume hypothesis is tested by combining those observations rather than reading a unique source depth from a hotspot's position.
A mantle plume is an upwelling of hot mantle material from deep within the Earth's mantle, typically originating from a boundary layer between the mantle and core or from the lower mantle. These plumes are thought to be caused by thermal convection within the Earth, where hot, less dense material rises while cooler, denser material sinks.
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