Mount Semeru erupts, ash plume 1 km high, alert issued

Indonesia’s Mount Semeru erupted on 28 June 2026, with four separate events recorded throughout the day. The strongest eruption at 11:37 WIB produced an ash column that reached about 1 000 metres (4 676 ft) above the summit. Seismic data showed maximum amplitudes of 22 mm and durations up to 203 seconds. The volcano is now on Level III (Siaga) alert. Authorities have prohibited any activity within a 13‑km sector southeast of the crater and within 500 metres of riverbanks in the Besuk Kobokan area, warning that hot ash clouds, lava fragments and lahars could travel up to 17 km from the peak. Residents are urged to stay clear of the crater’s five‑kilometre radius and monitor the Besuk Bang, Besuk Kembar and Besuk Sat valleys for possible flows.