[Abstract]

Torishima is an active insular volcano located on the Izu Arc (30°'N 140°'E, 394m). In the last century, big eruptions occurred in 1902 and 1939, which made the island uninhabitable. In 1998, a small pit crater was formed beside the Io-yama crater. A large-scale smoke rising from the insular volcano was observed on August 8, 2002. The phreatic eruption occurred after a dormancy of 63 years, resulting in the formation of the 2002 crater, and it was followed by magmatic eruptions with eject of scoria on August 10 and 12. Discolored water was observed on August 12 and 13. From August 13, emission of volcanic ash was intermittent and the volcanic activity ceased before August 19 at latest. The eruption in 2002 was relatively small-scale and short-term activity.

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