Map of the Earth's tectonic plates.

Based on a map prepared by the U.S. Geological Survey.

Like continental volcanoes, submarine volcanoes are most common where tectonic plates move towards or away from each other. In the case of divergent plate boundaries, where plates are spreading away from each other, the rate of plate movement plays an important role in determining the type of volcano that forms and the rate of eruptive activity. Submarine volcanoes at convergent plate boundaries (subduction zones) are much like their subaerial ("under air" or continental) counterparts except that the weight of the overlying water modifies their eruption style. Hot spots leave linear "tracks" of seamounts across the ocean basins and build some of Earth's largest volcanoes.