Volcano Semeru Eruption in Indonesia Triggers Emergency Relocations

Indonesia's Mount Semeru, the tallest summit on the island of Java, has exploded, blanketing several villages with falling ash, prompting evacuations and leading authorities to raise the warning to the maximum level.

The mountain in the province of East Java released searing clouds of hot ash and a mixture of stone, molten rock, and gases that moved up to 4 miles down its slopes multiple times from midday to dusk, while a thick column of hot clouds rose 2km into the sky, according to the nation's geological authority.

The outbursts that unfolded throughout the day forced officials to increase the volcano’s alert level twice, from the level three to the highest, the agency reported. No casualties have been announced.

More than 300 inhabitants in the three communities most at risk in the area of Lumajang were relocated to official safe havens, according to a spokesperson for the national emergency management body.

He stated that heightened volcanic movements of the volcano on Wednesday afternoon prompted authorities to expand the danger zone to 5 miles from the crater. Residents were advised to stay clear from an zone along the Kobokan River, which is the path of the lava flow, as searing gas flowed down Semeru’s slopes.

Footage on online platforms showed a thick plume of volcanic dust moving through a wooded ravine to a waterway beneath a bridge. Residents, some with faces smeared with ash and water, fled to makeshift refuges or departed for other safe areas.

Local media reported that emergency teams were struggling to rescue about 178 people trapped on the 3,676-metre peak at the Ranu Kumbolo monitoring post. The group included 137 climbers, 15 carriers, seven guides and six tourism officials, according to an spokesperson with the protected area.

“They are currently safe at Ranu Kumbolo monitoring post,” a spokesperson said in a video statement. He noted the station was located 4.5km from the summit on the northern slope of the mountain, which is not in the path of the hot cloud flow that was observed moving to the south-southeast. Bad weather and precipitation required the team to remain overnight there, he added.

Semeru, also known as Mahameru, has burst many occasions in the last two centuries. Still, as is the case with many of the 129 active volcanoes in the archipelago, thousands of residents still to live on its fertile slopes.

Semeru’s previous significant explosion was in late 2021, when 51 people were killed and several hundred more were burned and settlements were submerged in layers of mud. The eruption led to the evacuation of more than 10,000 residents from their homes.

Indonesia, an island chain of more than 280 million inhabitants, sits along the Pacific seismic belt, a horseshoe-shaped series of tectonic boundaries, and is prone to seismic events and volcanism.