Geologic Hotspots

Volcanoes often form where tectonic plates collide or pull apart. But sometimes they’ll form in the middle of plates, due to geologic hotspots. A hotspot is a plume of hot mantle that rises from within Earth, and heats, expands and deforms the crust above it, to create mountains, volcanoes or volcanic islands. The classic example is the chain of Hawaiian Islands, which formed as the Pacific plate traveled across a hotspot. Scientists always thought hotspots were stationary, while tectonic plates moved over them. But new research from beneath the Indian Ocean has challenged that idea. There, an undersea mountain range runs north-south for 3000 miles, along the 90-degree East longitudinal line. This long ridge was formed by a hotspot—but scientists studying the age and geologic makeup of each mountain on the chain realized they grew faster than could be possible by the plate alone moving. The hotspot must also have moved, possibly by hundreds of miles. This simple discovery will cause us to rethink hotspots and volcano formation, all over the world. It may turn out that other well-studied hotspots, like those beneath Iceland and Yellowstone, are moving too. Which could help us better understand the geothermal and volcanic activity there. And that’s how science works. It’s always on the move—sort of like hotspots.