The Hawaiian archipelago is a group of 132 islands, reefs, and shoals in the North Pacific Ocean that extends about 1,525 mi (2,454 km) from Kure Atoll (29°N, 178°W) to the big island of Hawaii (19°N, 156°W). This string of geographically remote and geologically unique volcanic islands makes up the U.S. state of Hawaii, and includes the eight main Hawaiian Islands of Ni'ihau, Kauai, Oahu, Molokai, Lanai, Maui, Kahoolawe, and Hawaii. The islands are progressively younger in geologic age toward the southeast; Kauai and Ni'ihau are about 5 million years in age, and the big island of Hawaii is less than 0.5 million years old. Indeed, new volcanic rocks are being deposited at Mt. Kilauea on Hawaii today.

The Hawaiian Islands are the exposed summits of the southernmost seafloor mountains, or seamounts, in the Hawaiian-Emperor seamount chain. This 3,105 mi (5,750 km) line of 107 volcanoes has formed over the last...