Northwestern Hawaiian Islands
The Northwestern Hawaiian Islands or Leeward Hawaiian Islands are a series of islands and atolls in the Hawaiian island chain located northwest of the islands of Kauai and Niʻihau. Politically, they are all part of Honolulu County in the U.S. state of Hawaii, except Midway Atoll, which is a territory distinct from the State of Hawaii, and grouped as one of the United States Minor Outlying Islands. The United States Census Bureau defines this area, except Midway, as Census Tract 114.98 of Honolulu County. Its total land area is 3.1075 square miles (8.048 km2). All the islands except Nihoa are north of the Tropic of Cancer, making them the only islands in Hawaii that lie outside the tropics.
The interior of Laysan, showing the hypersaline lake
JRO globe ca. 1960
The reserve sign on Lisianski
An atoll is a ring-shaped island, including a coral rim that encircles a lagoon. There may be coral islands or cays on the rim. Atolls are located in warm tropical or subtropical parts of the oceans and seas where corals can develop. Most of the approximately 440 atolls in the world are in the Pacific Ocean.
The atoll of Tetiꞌaroa in French Polynesia
Penrhyn atoll
NASA satellite image of some of the atolls of the Maldives, which consists of 1,322 islands arranged into 26 atolls
Nukuoro from space. Courtesy NASA