Image: University of Houston
Scientists at the University of Houston have uncovered the origin of the Tamu massif, the giant volcano, which is located in the Pacific ocean 1600 kilometers from Japan. It turned out that it is not a shield volcano, as previously thought, but was the result of spreading — moving apart of tectonic plates as a result of the discharge of magma. About it reported in a press release on Phys.org.
The researchers analyzed the map of the geomagnetic field over the array and found that the observed magnetic anomalies correspond to what are plate boundaries along mid-ocean ridges. Thus, the volcano formed in place of formation of new oceanic crust. Shield volcanoes are formed at constant liquid outpourings of magma from the summit and are one of the most common types of volcanoes.
The discovery changes the idea of how formed oceanic plateau structure such as the Tamu massif. According to a widely accepted model of mantle plumes rise toward the crust and form a large volcano, which is spewing huge amounts of basalt. For such processes characterized by the formation of horizontal layers of volcanic rock (young layers at the top, the ancient at the bottom). Similar is happening on the continent, and are known as flood basalts.
However, in mid-ocean ridges young rocks formed in the area of spreading, and the old recede to the sides. Therefore, the slopes of Tamu massif formed the flowing stream of magma, and the thickening and thinning of the ridge. Thus, the similarity between such structures as traps and oceanic plateau, is now under question.
Scientists emphasize that the Tamu massif can no longer be considered the largest shield volcano on Earth (this title returns to Mauna Loa in Hawaii) because it is a volcanic system. But it is also very huge, occupying an area of 450 by 650 kilometers, and a height reaching 4.5 kilometers.
Video, photo All from Russia.