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Tamu Massif
Tamu Massif is an extinct submarine shield volcano located in the northwestern Pacific Ocean. The possibility of its nature as a single volcano was announced on 5 September 2013, which, if corroborated, would make Tamu Massif the largest known volcano on Earth.〔 It is located in the Shatsky Rise about east of Japan. Its summit lies about below the surface of the ocean, and its base extends to a depth of about .〔 The volcano is about tall.
William Sager, a marine geophysicist from the Department of Earth and Atmospheric Sciences at the University of Houston, began studying the volcano in about 1993 at the Texas A&M College of Geosciences. According to Sager and his team, Tamu Massif is "the biggest single shield volcano ever discovered on Earth". While other igneous features on the planet are larger, such as the Ontong Java Plateau, it has not yet been determined if they are indeed just one volcano or rather complexes of several volcanoes.
==Geology==
The Tamu Massif was formed about 145 million years ago during the Late Jurassic to Early Cretaceous period〔 over a relatively short period of time (a few million years) and then became extinct.〔 If confirmed, the suggestion that it could be a single volcano in the Shatsky Rise would make it the largest known volcano on Earth, dwarfing the current record-holder, Mauna Loa on the Hawaiian Islands. Tamu's rounded dome extends over an area of , totaling more than , many times larger than Mauna Loa, which has an area of , and about half the area of the Martian volcano Olympus Mons. The entire mass of Tamu consists of basalt. Its slopes are very gradual, ranging from less than half a degree to one degree near its summit. While the Shatsky Rise oceanic plateau is comparable in size to California or Japan,〔 Tamu Massif, which is the plateau's oldest and largest edifice, is comparable in size to New Mexico〔 or Britain and Ireland together.〔
Using magnetic lineations, researchers discovered that there are three bathymetric highs and a low ridge, a topography that would imply three separate volcanoes; but the plume-head model indicates a single massive volcano.〔 Based on multichannel seismic profiles and rock samples from Integrated Ocean Drilling Program (IODP) core sites, Tamu Massif appears to be a single massive volcano made of lava flows that emanated from the volcano centre and formed its shield shape; however, the profiles have large gaps in them, leaving open the possibility that it may represent the activity of more than one volcano.〔
抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』
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