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The Mariana Islands (also the Marianas) are a crescent-shaped archipelago comprising the summits of fifteen mostly dormant volcanic mountains in the western North Pacific Ocean, between the 12th and 21st parallels north and along the 145th meridian east. They lie south-southeast of Japan, west-southwest of Hawaii, north of New Guinea and east of the Philippines, demarcating the Philippine Sea's eastern limit. They are found in the northern part of the western Oceanic sub-region of Micronesia, and are politically divided into two U.S. jurisdictions: the Commonwealth of the Northern Mariana Islands and, at the southern end of the chain, the territory of Guam. The islands were named after Queen Mariana by Spaniards, who first arrived in the early 16th century and who eventually annexed and colonized the archipelago. The indigenous inhabitants are the Chamoru. Archaeologists in 2013 reported findings which indicated the people who first settled the Marianas arrived there after making what was at that time the longest uninterrupted ocean voyage in human history. They further reported findings which suggested that Tinian is likely to have been the first island in Oceania to have been settled by humans. == Description == The Mariana Islands are the southern part of a submerged mountain range that extends from Guam to near Japan. Geographically, the Marianas are the northernmost islands of a larger island group called Micronesia, situated between 13° and 21°N latitude and 144° and 146°E longitude. The Mariana Islands have a total land area of .〔(''The CIA World Factbook'' (2006) ).〕 They are composed of two administrative units: * Guam, a US territory * the Northern Mariana Islands (including the islands of Saipan, Tinian and Rota), which make up a Commonwealth of the United States. The island chain geographically consists of two subgroups, a northern group of ten volcanic main islands, all are currently uninhabited; and a southern group of five coralline limestone islands (Rota, Guam, Aguijan, Tinian and Saipan), all inhabited except Aguijan. In the northern volcanic group a maximum elevation of about is reached; there are craters showing signs of activity, and earthquakes are not uncommon. Coral reefs fringe the coasts of the southern isles, which are of slight elevation. The lowest point on the Earth's crust, the Mariana Trench, is near the islands and is named after them. The islands are part of a geologic structure known as the Izu-Bonin-Mariana Arc system, and range in age from 5 million years old in the north to 30 million years old in the south (Guam). The island chain arises as a result of the western edge of the Pacific Plate moving westward and plunging downward below the Mariana plate, a region which is the most volcanically active convergent plate boundary on Earth. This subduction region, just east of the island chain, forms the noted Mariana Trench, the deepest part of the Earth's oceans and lowest part of the surface of the Earth's crust. In this region, according to geologic theory, water trapped in the extensive faulting of the Pacific Plate as serpentinite, is heated by the higher temperatures of depth during its subduction, the pressure from the expanding steam results in the hydrothermal activity in the area and the volcanic activity which formed the Mariana Islands.〔(Geology of Mariana Islands. Accessed June 28, 2009 )〕 All the islands, except Farallon de Medinilla and Uracas or Farallon de Pajaros (in the northern group), are more or less densely wooded, and the vegetation is dense, much resembling that of the Carolines and also of the Philippines, from where species of plants have been introduced. Owing to the moistness of the soil cryptogams are numerous, as are also most kinds of grasses. On most of the islands there is a plentiful supply of water. The fauna of the Marianas, though inferior in number and variety, is similar in character to that of the Carolines and certain species are indigenous to both island groups. The climate though damp is healthy, while the heat, being tempered by the trade winds, is milder than that of the Philippines; the variations of temperature are not great. The majority of islands in the Marianas which still retain their indigenous names end in the letters -an; e.g. Guahan (the indigenous name of Guam), Agrigan, Agrihan, Aguihan/Aguigan, Pagan, Sarigan, etc. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Mariana Islands」の詳細全文を読む スポンサード リンク
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