JMA reported that an eruptive event at Iodake Crater located at Satsuma Iwo-jima, a subaerial part of Kikai’s NW caldera rim, was recorded at 1128 on 1 September. An ash plume rose 1 km above the crater rim. The report noted that there was no change in the number of earthquakes either before or after the event, and no volcanic tremors were recorded. An eruptive event at 1008 on 3 September generated a volcanic plume that rose 700 m above the crater rim. Crater incandescence continued to be observed at night. The 1 September event was the first eruptive activity since 6 October 2020. The Alert Level remained at 2 (on a 5-level scale), and residents were warned to stay 500 m away from Iodake Crater.

Geological Summary. Multiple eruption centers have exhibited recent activity at Kikai, a mostly submerged, 19-km-wide caldera near the northern end of the Ryukyu Islands south of Kyushu. It was the source of one of the world's largest Holocene eruptions about 6,300 years ago when rhyolitic pyroclastic flows traveled across the sea for a total distance of 100 km to southern Kyushu, and ashfall reached the northern Japanese island of Hokkaido. The eruption devastated southern and central Kyushu, which remained uninhabited for several centuries. Post-caldera eruptions formed Iodake (or Iwo-dake) lava dome and Inamuradake scoria cone, as well as submarine lava domes. Recorded eruptions have occurred at or near Satsuma-Iojima (also known as Tokara-Iojima), a small 3 x 6 km island forming part of the NW caldera rim. Showa-Iojima lava dome (also known as Iojima-Shinto), a small island 2 km E of Satsuma-Iojima, was formed during submarine eruptions in 1934 and 1935. Mild-to-moderate explosive eruptions have occurred during the past few decades from Iodake, a rhyolitic lava dome at the eastern end of Satsuma-Iojima.

Source: Japan Meteorological Agency (JMA)