The Japan Meteorological Agency (JMA) reported that activity continued at Shinmoedake (Shinmoe peak, a stratovolcano of the Kirishimayama volcano group) during 26 August-2 September. Fumarolic plumes rose as high as 100 m above the fissures on the W flank. The number of volcanic earthquakes located beneath Shinmoedake, first detected in late October 2024, continued to be frequent; a short-duration volcanic tremor was detected around 0800 on 31 August. At 0453 on 28 August an ash plume rose 5.5 km above the crater rim and drifted S. Significant ashfall reported in areas downwind, including in Kirishima City (21 km SW) and Miyakonojo City (30 km SE), was enough to obscure the lines on some roads. Ashfall was also reported in Soo City (32 km SSE) and Kanoya City (60 km S). Ash plumes were continuous through the morning and early afternoon; the plumes rose 4.5 km above the crater rim and drifted S at 0523, then rose to 3.7 km at 0900 before stopping at 1450. A period of ash emissions was recorded from 1823 on 28 August to 0830 on 29 August, with ash plumes rising 700-1,300 m above the crater rim and occasionally drifting N. Continuous ash plumes rose as high as 600 m above the crater rim and drifted N during 0542-0830 on 30 August. At 1323 on 30 August an ash plume rose 300 m above the crater rim ana drifted NW. The Alert Level remained at 3 (on a 5-level scale) and the public was warned to exercise caution within 3 km from Shinmoedake Crater.

Geological Summary. Kirishimayama is a large group of more than 20 Quaternary volcanoes located north of Kagoshima Bay. The late-Pleistocene to Holocene dominantly andesitic group consists of stratovolcanoes, pyroclastic cones, maars, and underlying shield volcanoes located over an area of 20 x 30 km. The larger stratovolcanoes are scattered throughout the field, with the centrally located Karakunidake being the highest. Onamiike and Miike, the two largest maars, are located SW of Karakunidake and at its far eastern end, respectively. Holocene eruptions have been concentrated along an E-W line of vents from Miike to Ohachi, and at Shinmoedake to the NE. Frequent small-to-moderate explosive eruptions have been recorded since the 8th century.

Source: Japan Meteorological Agency (JMA)