Indonesia's Mount Semeru erupts, blanketing villages with ash and prompting evacuations

The eruptions that unfolded throughout the day forced authorities to raise the volcano’s alert level twice, from the third-highest level to the highest, the agency said. No casualties have been reported.

More than 300 residents in the three villages most at risk in the district of Lumajang were evacuated to government shelters, said National Disaster Mitigation Agency's spokesperson Abdul Muhari.

He said increased activity of the volcano on Wednesday afternoon prompted authorities to widen the danger zone to 8 kilometers (5 miles) from the crater. People were advised to keep away from an area along the Besuk Kobokan River, which is the path of the lava flow as searing gas flowed down Semeru's slopes.

Videos on social media showed a dense cloud of ash sweeping through a forested valley to a river beneath a bridge. Residents, some with faces smeared with volcanic dust and rain, fled to temporary shelters or left for other safe areas.

Local media reported that authorities are struggling to rescue about 178 people stranded on the 3,676-meter (12,060-foot) mountain at the Ranu Kumbolo monitoring post. The group includes 137 climbers, 15 porters, 7 guides and 6 tourism officials, according to an official with the Bromo-Tengger-Semeru National Park, TNBTS.

“They are currently safe at Ranu Kumbolo monitoring post,” Endrip Wahyutama, a TNBTS spokesperson, said in video statement, adding that the post is located 4.5 kilometers (2.7 miles) from the crater on the northern slope of the mountain, which is not in the path of the hot cloud flow that was observed moving to south-southeast. Bad weather and rain forced them to spend the night there, he said.

Semeru, also known as Mahameru, has erupted numerous times in the past 200 years. Still, as is the case with many of the 129 active volcanoes in Indonesia, tens of thousands of people continue to live on its fertile slopes.

Semeru’s last major eruption was in December 2021 when it left 51 people dead and several hundred others burned in villages that were buried in layers of mud. The eruption forced the evacuation of more than 10,000 people. The government moved about 2,970 houses out of the danger zone.

Indonesia, an archipelago of more than 280 million people, sits along the Pacific “Ring of Fire,” a horseshoe-shaped series of fault lines, and is prone to earthquakes and volcanic activity.