A mantle plume is a column or narrow upwell of unusually hot mantle material that rises from deep inside the Earth's mantle toward the surface. As this hot material ascends, it is more buoyant than the surrounding mantle and can cause partial melting as it nears the base of the lithosphere, which can feed volcanic activity at the surface. Mantle plumes are often invoked to explain volcanic hotspots (like Hawaii and Iceland) that do not align with plate boundaries, as well as large igneous provinces (e.g., Deccan Traps, Siberian Traps) that reflect substantial, sustained magmatic output. Key points

• Origin and rise: Plumes are thought to originate deep in the mantle, potentially near the core–mantle boundary, and rise as narrow, buoyant columns due to thermal buoyancy.
• Surface expressions: When a plume head reaches shallow depths, it can cause significant melting and surface volcanism, creating hotspots and large igneous provinces.
• Plate tectonics context: Some hotspots appear stationary relative to the mantle while plates move over them, producing age-progressive island chains or volcanic tracks.
• Competing views: While the plume hypothesis is widely taught, there is ongoing scientific debate about plume initiation, mantle flow, and alternative explanations for hotspot volcanism and intraplate magmatism.

If you’d like, I can summarize how the plume concept fits with specific hotspots (e.g., Hawaii, Iceland) or outline the main lines of evidence for and against mantle plumes.