OPEN Scientific reports | 11 Feb 2018
Y Tatsumi, K Suzuki-Kamata, T Matsuno, H Ichihara, N Seama, K Kiyosugi, R Nakaoka, K Nakahigashi, H Takizawa, K Hayashi, T Chiba, S Shimizu, M Sano, H Iwamaru, H Morozumi, H Sugioka and Y Yamamoto
Kikai submarine caldera to the south of the Kyushu Island, SW Japan, collapsed at 7.3 ka during the latest supereruption (>500 km3 of magma) in the Japanese Archipelago. Multi functional research surveys of the T/S Fukae Maru in this caldera, including multi-beam echosounder mapping, remotely operated vehicle observation, multi-channel seismic reflection survey, and rock sampling by dredging and diving, provided lines of evidence for creation of a giant rhyolite lava dome (~32 km3) after the caldera collapse. This dome is still active as water column anomalies accompanied by bubbling from its surface are observed. Chemical characteristics of dome-forming rhyolites akin to those of presently active small volcanic cones are different from those of supereruption. The voluminous post-caldera activity is thus not caused simply by squeezing the remnant of syn-caldera magma but may tap a magma system that has evolved both chemically and physically since the 7.3-ka supereruption.
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