Apr. 27, 1999 An active volcano rising more than 4,300 meters (some 14,100 feet) from the ocean floor in the Samoa Islands has been discovered by a team of National Science Foundation (NSF)-funded scientists, providing more evidence in the scientific debate over the formation of hot spot island chains. The volcano, more than 35 kilometers (about 22 miles) across at its base, rises to within 600 meters (about 2,000 feet) of the surface. Its peak is marked by a circular caldera some two kilometers (about one mile) across and 400 meters (1,300 feet) deep. It is similar in size to Mt. Whitney in California, the U.S. largest mountain in the contiguous 48 states.
"The discovery underscores just how little we know about the ocean floor," says Dave Epp, program director in NSF's division of ocean sciences which funded the research. "A major, and perhaps active, volcano was found in an area that might be considered well surveyed."
The new volcano was discovered by Stan Hart, a geochemist at the Woods Hole Oceanographic Institution, and colleagues. The location had been predicted based on a 1995 earthquake swarm in the region. The volcano has been named Fa'afafine, a Samoan word that very loosely translated means "wolf in sheep's clothing. It seemed an appropriate name since the size of the volcano was a surprise," Hart says. "The available bathymetric maps of the area gave us no indication of what was really there on the ocean floor."
The existing maps of the seafloor in the area, made by satellite altimetry a few years ago and considered the most accurate maps available, gave little indication of the actual size of the volcano. They simply showed a small hill-like geologic feature, one of many unnamed features in the island chain. Hart, whose research focuses on the formation of the earth's mantle and the evolution of hot spots, decided to look closer at several of the features. A detailed survey with the research vessel Melville revealed the true size of the volcano, and the stunning perfection of the summit caldera, along with the first detailed information about other features on the ocean floor around several of the nearby islands.
Hart and his colleagues went to the area to test the idea that the Samoa Islands are a volcanic hot spot chain, and to prove that their formation is not principally related to proximity to the nearby Tonga Trench, as some earth scientists believe. The classic example of a hot spot island chain is the Hawaiian Islands, where what will someday be the newest island, Loihi, is a seamount rising toward the ocean surface on the southeast flank of the island of Hawaii. These volcanic chains are formed as the Pacific lithospheric plate migrates slowly northwest over a hot upwelling of the underlying mantle. Hart believes that the Samoa Islands chain, like the Hawaiian Islands, is indeed such a hot spot chain, with the youngest volcano at the end of the chain. Fa'afafine, at the far eastern end of the Samoa Island chain, likely represents the present location of the "hotspot."
Hart and his colleagues are planning a return trip to the volcano, and are hoping to use a remotely-operated vehicle or human-occupied submersible to survey the caldera in detail, and to search for hydrothermal hot springs and associated biota.
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