Hawaii is the most recent of the 50 U.S. states (joined the Union on August 21, 1959), and is the only U.S. state made up entirely of islands. It is the northernmost island group in Polynesia, occupying most of an archipelago in the central Pacific Ocean.
Hawaii’s diverse natural scenery, warm tropical climate, abundance of public beaches, oceanic surroundings, and active volcanoes make it a popular destination for tourists, (wind)surfers, biologists, and volcanologists alike. Due to its mid-Pacific location, Hawaii has many North American and Asian influences along with its own vibrant native culture. Hawaii has over a million permanent residents along with many visitors and U.S. military personnel. Its capital is Honolulu on the island of Oʻahu.
The state encompasses nearly the entire volcanic Hawaiian Island chain, which comprises hundreds of islands spread over 1,500 miles (2,400 km). At the southeastern end of the archipelago, the eight "main islands" are (from the northwest to southeast) Niʻihau, Kauaʻi, Oʻahu, Molokaʻi, Lānaʻi, Kahoʻolawe, Maui and the island of Hawaiʻi. The last is the largest and is often called "The Big Island" to avoid confusing the name of the island with the name of the state as a whole. The archipelago is physiographically and ethnologically part of the Polynesian subregion of Oceania.
The Hawaiian islands were (and continue to be) continuously formed from volcanic activity initiated at an undersea magma source called a hotspot. As the tectonic plate beneath much of the Pacific Ocean moves to the northwest, the hot spot remains stationary, slowly creating new volcanoes. Due to the hotspot’s location, the only active volcanoes are located around the southern half of the Big Island. The newest volcano, Lōʻihi Seamount, is located south of the Big Island’s coast.
The last volcanic eruption outside the Big Island occurred at Haleakalā on Maui before the late 18th century, though it could have been hundreds of years earlier. In 1790, Kīlauea exploded with the deadliest eruption (of the modern era) known to have occurred in what is now the United States. As many as 5,405 warriors and their families marching on Kīlauea were killed by that eruption.
Volcanic activity and subsequent erosion have created impressive geological features. The Big Island has the third highest point among the world’s islands.
Slope instability of the volcanoes has generated damaging earthquakes with related tsunamis, particularly in 1868 and 1975. Steep cliffs have been caused by catastrophic debris avalanches on the submerged flanks of ocean island volcanos.