Everything on Earth, from the mountains to the oceans rests on a thin brittle layer of rock called the crust. This crust is broken into sections called tectonic plates that move around on top of a more flexible (and very hot) layer of rock called the mantle. But not every single place in the mantle is created equal. Just like on a finicky stove, there are sometimes areas of the mantle that get much hotter than others. This heat is often concentrated in a small area, and melts the crust like a blowtorch, creating a volcano in that spot. While plates can move, these hotspots tend to stay in one place.