The Hawaiian Islands rise above an elongated submarine platform or ridge that stretches for almost 2000 statute miles in a southeast to northwest direction, between the parallels of 18° 40′ to 28° 40′ north, and, the meridians of 154° 30′ to 178° 40′ west. The platform is supposedly constructed of volcanic materials that were erupted from a zone of fissures on the ocean floor; besides the visible islands there are several submarine peaks and numerous banks.
The Hawaiian chain can be divided into three sections based on the nature of the islands and the stage of erosion. The southeastern portion is about 400 miles long, and embraces eight high volcanic islands that are only moderately reduced by erosion. These islands are Hawaii (4030 square miles), Maui (728), Lanai (141), Kahoolawe (45), Molokai (260), Oahu (604), Kauai (555), and Niihau (72). The seven largest islands contain all the population of the Territory, Kahoolawe now being uninhabited.
The middle segment is nearly 800 miles long, from little Kaula near Niihau to beyond Gardner, and includes five islets or stacks of volcanic rock, Kaula, Nihoa, Necker, La Perouse Pinnacle, and Gardner Pinnacles, besides French Frigate Shoals and several banks that have resulted from the erosion of volcanic islands. Both Necker Island (41 acres) and Nihoa Island (155 acres) show evidence of a former occupation by man but were abandoned before the arrival of Europeans. La Perouse Pinnacle rises from the bank of French Frigate Shoals. During the Second World War an airfield was developed on the low land within the reef of the shoals, but it was deactivated after the close of the conflict.
The northwestern section, which is about 700 miles long, consists of low atolls, sandy islets, reefs, and shoals wih no visible volcanic rock because the upper portion of the volcanoes that once existed have been eroded below sea level, and their truncated cones form the platform on which coral grew to form reefs and islands. From east to west the islands are Laysan, Pearl and Hermes Reef (an atoll), Midway, and Kure or Ocean Island. Laysan and Kure are included in the Hawaiian Islands Bird Reservation, which comprises all the islands as far east as Nihoa. None of these islands contains permanent human inhabitants except Midway. Guano has been mined on Laysan, which once supported millions of sea birds, now much reduced in numbers.