Satsuma-Iojima fumaroles

Satsuma-Iojima is a small volcanic island located in Kagoshima Prefecture in southern Japan. The island is part of the Kikai caldera, a massive mostly-submarine volcanic structure in the East China Sea, and lies south of Kyushu, the southernmost of Japan's four main islands.

The fumaroles on Satsuma-Iojima emit large volumes of sulfur dioxide, hydrogen sulfide, and other volcanic gases associated with the island's active geothermal system. These sulfur-rich emissions are intense enough that the island was historically used for sulfur mining, and the deposited sulfur can be seen as yellow crusts around active vent areas.

Satsuma-Iojima can be reached by ferry from Kagoshima, and a small population continues to live on the island despite the intense volcanic activity. Visitors can observe fumarolic activity and natural hot springs, but must exercise caution due to high concentrations of volcanic gases — particularly sulfur dioxide — in certain low-lying and vent-adjacent areas.

Yes, Satsuma-Iojima sits on the rim of the Kikai caldera, which produced one of the largest Holocene eruptions in the Japanese archipelago approximately 7,300 years ago during the Jomon period. The caldera remains active, and the intense fumarolic activity on Satsuma-Iojima is a surface expression of the large magmatic system beneath the surrounding waters.