Tern Island is part of the Hawaiian Islands. The largest of the Hawaiian Islands are at the southeast end of the chain, and these are permanently inhabited by people. The rest of the islands in the chain are part of the State of Hawaii, but have few inhabitants and these are mostly field scientists. They are the Hawaiian Islands National Wildlife Refuge, and they are administered by the United States Fish and Wildlife Service. The Hawaiian Islands are the most isolated pieces of land on the planet.
Tern Island is in the middle of Hawaiian Islands chain.
The chain is the tops of tall volcanoes that were produced by a hotspot , an opening in the ocean floor that periodically produces enough lava to make an island that breaks the ocean surface. A large piece of the Earth's crust moves northwest over that hotspot, carrying the newly formed mountains to the northwest. Over time the mountains sink below the surface of the ocean due to their great weight and also erosion from wind and rain. As a result, the youngest islands in the Hawaiian chain also have the most land area above the ocean surface. These young islands are at the southeast end of the chain, and the youngest, the island Hawaii, is over the hotspot and is volcanically active.