Rare audio of approaching pyroclastic flow from Mount Semeru’s November 19 eruption, East Java
A major eruption at Mount Semeru, East Java, Indonesia, on November 19, 2025, produced large pyroclastic flows descending the southern slopes. One of them was captured on video, allowing both the sight and sound of the approaching flow to be recorded.
The video shows a large pyroclastic density current moving downslope at high speed, generating a continuous, resonant rumble audible for kilometers.
The sound originates from turbulent, high-temperature gas and ash surging through the valley, with particle collisions and rapid pressure oscillations producing the characteristic low-frequency vibration.
Short, thunder-like bursts accompany the flow as electrical discharges occur within the moisture-rich ash column. Volcanic lightning events are produced when fine ash particles collide and accumulate charge, releasing short flashes and sharp acoustic cracks. Light rainfall and ashfall can also be heard striking nearby surfaces.
During this event, the AfarTV monitoring cameras positioned near the volcano went offline amid extreme ashfall and intense eruptive activity. According to the network’s operators, the outage likely resulted from ash accumulation and high-temperature exposure affecting the equipment. “We are assessing the situation, but the equipment may have been damaged by the eruption,” the team said.
The eruption began early on November 19, 2025, producing multiple pyroclastic density currents and sending an ash plume up to 17.9 km (59 000 feet) above the summit. Heavy ashfall was reported across the Lumajang region, prompting authorities to raise the alert to Level IV, the highest on Indonesia’s four-tier volcanic alert scale.
More than 900 residents were evacuated from villages on the southern slopes, particularly along the Besuk Kobokan valley, where several pyroclastic flows reached distances of up to 13 km (8 miles) from the summit. Thick deposits of ash and volcanic material disrupted transportation, damaged crops, and reduced visibility to near zero in several communities.
At the same time, rescue teams were deployed to assist a group of about 170 climbers and guides who had been stranded near Ranu Kumbolo on the northern slope of the volcano. The evacuation was completed the following day, with all climbers reported safe.
Featured image: Volcanic lightning and large pyroclastic flow produced during major eruption at Semeru volcano on November 19, 2025. Credit: afarTV
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Having never heard a pyroclastic flow before I was intrigued by it.
However I am puzzled that the sound track didn’t change as the first flow reached its maximum distance and started receding/rising.