The Semeru volcano is one of the most active in the Indonesian archipelago. In the last 24 hours, it has erupted more than a dozen times, emitting enormous clouds of ash and hurling lava and rocks up to 15.5 kilometers down the mountainside. The volcanology department has raised the alert level for Semeru volcano to IV (the highest on the Indonesian scale) following the eruptions, which sent pyroclastic flows down the mountainside. Authorities have established an exclusion zone with a radius of 8 kilometers from the crater. Pyroclastic flows are dangerous avalanches of gas, ash, and fragments of volcanic rock that descend at high speed down the slopes of volcanoes.

Climbers out of danger

The eruptions were mainly recorded on the southeast face of the volcano, so they did not endanger a group of climbers who were ascending on the north side.

As a result of the volcanic activity, the 137 climbers took refuge in an area known as Ranu Kumbulo, about 8 kilometers from the crater, where they spent the night before being evacuated.

On Thursday, November 20, 2025, some of the villages located on the slopes of the volcano and the roads in the area appeared covered by a thick blanket of ash, as the population gathered their belongings to temporarily leave their homes.