"A large submarine volcano rises to within 65 m of the sea surface west of Tongatapu Island. The volcano was informally named Volcano #1 by the scientists on the bathymetric survey that discovered the submarine volcano in 2003. The summit of the andesitic-to-dacitic volcano is cut by a large 7 x 4.5 km wide caldera, with two young scoria cones forming the high point of the seamount. A chain of explosion craters up to 100 m deep cut the flank of one of the scoria cones, and thick deposits of ash and scoria blanket the caldera floor nearby. The lack of organic sediments between volcaniclastic deposits exposed in one portion of the caldera wall suggest it was constructed within the past 200 years. Diffuse low-temperature hydrothermal vents and vigorous gas discharge occurs near the explosion craters."  -Smithsonian Volcano Archive
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