Mount Semeru eruption sends pyroclastic flow 6 km (3.7 miles) down southeastern flank, Indonesia

Multiple eruptions at Mount Semeru in East Java, Indonesia, on February 13 and 14, 2026, produced pyroclastic flows up to 6 km (3.7 miles) down the volcano’s southeastern flank and ash plumes up to 2 000 m (6 500 feet) above the crater. PVMBG maintains a 13 km (8 miles) exclusion zone in the southeastern sector.

Mount Semeru volcano in East Java, Indonesia, experienced multiple eruptions between February 13 and 14, producing large pyroclastic flows and ash emissions.

The most significant activity occurred at 05:54 LT on February 14 (22:54 UTC on February 13), when pyroclastic flows traveled approximately 6 km (3.7 miles) from the summit toward the Besuk Kobokan river valley on the southeastern flank. Ashfall was mostly confined to the upper slopes.

The eruption column rose about 2 000 m (6 561 feet) above the summit, with dense gray ash drifting north and northeast. A subsequent event at 07:25 LT produced another ash plume reaching 1 500 m (4 921 feet).

Earlier eruptions on Friday morning, February 13, generated pyroclastic flows up to 3 km (1.9 miles) down the southeastern slope, followed by additional flows of about 2.5 km (1.6 miles) at 14:22 LT and 14:31 LT.

According to the Center for Volcanology and Geological Hazard Mitigation (PVMBG), the volcano remains at Alert Level III (Watch) — the second-highest level in Indonesia’s four-tier warning system. PVMBG maintains a 13 km (8 miles) exclusion zone in the southeastern sector, particularly along the Besuk Kobokan drainage, where pyroclastic density currents and lahars pose continuing danger.

Pyroclastic flows consist of high-temperature gas, ash, and volcanic rock fragments that can exceed 1 000°C (1 832°F) and move at a speed of several hundred km/h. They represent the primary hazard on the Semeru’s flanks, often following the same channels affected by previous eruptions.

Semeru, also known as Mahameru (“Great Mountain”), rises 3 657 m (11 998 feet) above sea level and is the highest peak on Java. It is one of Indonesia’s most persistently active volcanoes, showing near-continuous explosive and effusive behavior.

PVMBG reported 39 eruptions during the week preceding February 13 and a cumulative total of 308 events since January 2026.

The eruptions occurred during Indonesia’s rainy season, when heavy precipitation increases the probability of lahars (volcanic mudflows that form when loose ash and debris mix with rainfall) along rivers draining the southeastern sector.

Authorities advise residents and tourists to remain outside the restricted area and stay alert to lahar warnings during periods of heavy rain.

Featured image: Pyroclastic flow at Mount Semeru, Indonesia, at 07:28 local time on February 14, 2026. Credit: afarTV