Hotspots are fixed plumes of unusually hot mantle material that rise toward the surface and feed volcanoes in the interior of a tectonic plate, away from the usual plate boundaries where most volcanism occurs.
- The mantle plume stays roughly stationary while the plate drifts over it, so a chain of volcanoes is created, with the youngest and active volcano over the plume and progressively older, extinct ones trailing away.
- The classic example is the Hawaiian island chain in the Pacific: the Big Island (with Mauna Loa and Kilauea) sits over the hotspot, while older islands lie to the northwest.
- The Yellowstone caldera in the USA, Reunion and the Deccan Trap (linked by some to the Reunion plume), and Iceland (a hotspot on a mid-ocean ridge) are other examples.
- Hotspot volcanism differs from boundary volcanism: it occurs within plates (intraplate), not at subduction zones or rifts, and is fed by deep mantle, usually producing basaltic shield volcanoes.
- The concept was proposed by J Tuzo Wilson (1963) to explain volcanic chains far from plate margins.
The idea of a fixed plume with a moving plate, the Hawaiian chain as the textbook example, and the link to the Deccan and Yellowstone connect to plate tectonics and volcanic landforms.
Hotspot volcanism is intraplate (within a plate) unlike the boundary volcanism of the Ring of Fire; the plume is fixed and the plate moves, not the other way round; hotspots usually give gentle basaltic shields, not explosive composite cones.
A fixed mantle plume under a moving plate that builds a chain of volcanoes, as in Hawaii.