Most volcanoes form at the edges of tectonic plates. Hot spot volcanoes are different. Hot spots are places where molten rock erupts out of the middle of a tectonic plate. A large pool of magma forms in the mantle just beneath the crust at a hot spot. The magma erupts as a volcano. The magma pool in the mantle is fixed in place, and over time, the tectonic plate above the hot spot moves. As it moves, a new volcano forms. This process eventually makes a chain of volcanic mountains. Only the youngest volcano is active. The figure below shows some of the Hawaiian Islands, which are part of a hot spot chain.