As a tectonic plate moves over a mantle hotspot, a chain of volcanoes is produced. The most famous of these chains is the Hawaiian Islands & Emperor Seamounts in the Pacific Ocean. These islands and seamounts are age progressive. The youngest island, Hawaii, is volcanically active and is where the crust is currently located over the hotspot. As the crust moves, another island will eventually form- in fact, one is forming underwater now, and it is named Loihi! Behind the main island of Hawaii, there are other, older islands that are not currently volcanically active. Beyond the islands, there is a long chain of underwater seamounts- these seamounts used to be subaerial islands but because of subsidence and erosion they are now underwater hotspot remnants.