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Sfondo:A massive volcanic seamount, not discovered until 1975, rises 4200 m from the sea floor to a depth of 590 m about one-third of the way between Ta'u and Rose islands at the eastern end of the American Samoas. The basaltic seamount, named Vailulu'u, is considered to mark the current location of the Samoan hotspot. The summit of Vailulu'u contains a 2-km-wide, 400-m-deep oval-shaped caldera. Two principal rift zones extend east and west from the summit, parallel to the trend of the Samoan hotspot, and a third less prominent rift extends SE of the summit. The rift zones and escarpments produced by mass wasting phenomena give the seamount a star-shaped pattern. On July 10, 1973, explosions from Vailulu'u were recorded by SOFAR (hydrophone records of underwater acoustic signals). An earthquake swarm in 1995 may have been related to an eruption from the seamount. Turbid water above the summit shows evidence of ongoing hydrothermal plume activity.
Smithsonian / GVP volcano information
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