Indonesia Volcano Eruptions Hit Ibu, Lewotobi and Semeru on 18 August 2026
Three active Indonesia volcano sites erupted in rapid succession on Tuesday night, 18 August 2026, with ash plumes rising from each site and authorities issuing immediate safety guidance. The Geological Agency under the Ministry of Energy and Mineral Resources recorded the events and confirmed ongoing alert levels at all three locations.
Overview of the Sequential Eruptions
Mount Ibu, Mount Lewotobi Laki-laki, and Mount Semeru erupted within hours of one another on Tuesday night. [1] Mount Ibu produced three separate blasts between 20:36 WIT and 23:11 WIT, while Mount Lewotobi Laki-laki erupted at 21:09 WITA and Mount Semeru at 20:33 WIB. [2] The Geological Agency noted that the eruptions occurred in close succession, with seismic instruments capturing each event even when visual confirmation was limited by weather. [3] All three sites remain under active monitoring, and the agency released detailed reports the following day. [4]
Eruption Details for Mount Ibu
Mount Ibu in West Halmahera, North Maluku, recorded three consecutive eruptions. [5] The first occurred at 20:36 WIT and produced an ash column 700 meters above the summit. [1] A second eruption followed at 20:58 WIT with a 500-meter ash column. [2] The third eruption took place at 23:11 WIT, sending a 600-meter column of grey-white ash drifting northeast and east. [3] The volcano remains at Level II (Waspada). [4]
Ash plume rises from erupting Mount Semeru in Lumajang during sequential Indonesian volcano eruptions. — Source: antaranews
Activity at Mount Lewotobi Laki-laki
Mount Lewotobi Laki-laki in East Flores, East Nusa Tenggara, erupted once at 21:09 WITA. [5] The event produced a dense grey ash column 300 meters high that drifted west and northwest. [1] Seismic instruments registered a maximum amplitude of 11 millimeters lasting 109 seconds. [2] The volcano is currently at Level III (Siaga). [3]
Semeru Eruption and Seismic Recording
Mount Semeru in East Java erupted at 20:33 WIB. [4] Thick fog prevented visual observation of any plume, yet seismographs recorded an eruption tremor with a maximum amplitude of 22 millimeters that lasted 235 seconds. [5] The volcano remains at Level III (Siaga). [1]
Ash plume rises from erupting Mount Semeru during sequential Indonesian volcano eruptions on 18 August 2026. — Source: gdelt
Safety Recommendations and Exclusion Zones
Authorities have prohibited all activity in the southeast sector along Besuk Kobokan up to 13 kilometers from Mount Semeru’s summit. [2] Residents must also remain at least 500 meters from riverbanks along Besuk Kobokan up to 17 kilometers downstream because of the risk of pyroclastic flows and lahar. [3] A 5-kilometer radius around the crater is closed to all activity due to the danger of incandescent rockfall. [4] The Geological Agency emphasized that these zones are in force while the volcano stays at Level III. [5]
Official Response and Monitoring
The Geological Agency under the Ministry of Energy and Mineral Resources issued the eruption reports and safety recommendations. [1] The agency compiled data from its monitoring stations and released statements confirming the alert levels at each volcano. [2] Public advisories stress compliance with the exclusion zones to reduce exposure to ash, pyroclastic flows, and rockfall hazards. [3]
What to watch next: Continued seismic monitoring at all three sites will determine whether alert levels are adjusted or additional restrictions are required.
