Mount Mahameru Outburst in Indonesia Triggers Evacuations

The nation's Mount Semeru, the highest peak on the island of Java, has erupted, blanketing multiple communities with volcanic ash, prompting evacuations and causing officials to elevate the warning to the maximum level.

The mountain in East Java province released blistering plumes of fiery ash and a combination of rock, lava and gas that travelled up to 4 miles down its slopes multiple times from midday to evening, while a dense plume of fiery clouds rose 2km into the sky, according to Indonesia’s Geology Agency.

The eruptions that occurred throughout the day forced authorities to increase the mountain's warning status on two occasions, from the level three to the top level, the authority reported. No casualties have been reported.

Over three hundred inhabitants in the three communities most at risk in the area of Lumajang region were relocated to official safe havens, according to a spokesperson for the national disaster mitigation agency.

He stated that increased activity of the mountain on Wednesday afternoon prompted officials to widen the danger zone to 8km from the summit. Residents were advised to stay clear from an area along the Besuk Kobokan River, which is the route of the lava flow, as scorching gases flowed down Semeru’s slopes.

Videos on online platforms showed a dense cloud of volcanic dust moving through a wooded ravine to a river beneath a bridge. Locals, some with faces covered with volcanic dust and rain, escaped to makeshift refuges or departed for other safe areas.

Local media indicated that emergency teams were struggling to rescue about 178 people trapped on the 3,676-metre mountain at the Ranu Kumbolo monitoring post. The group comprised 137 climbers, 15 porters, seven escorts and six tourism officials, according to an official with the national park.

“They remain secure at Ranu Kumbolo monitoring post,” a spokesperson said in a recorded message. He said the post was located 4.5km from the crater on the north side of the mountain, which is outside the trajectory of the fiery cloud movement that was seen moving to the south-southeast. Inclement conditions and rain required the team to remain overnight there, he added.

The volcano, also called Mahameru, has burst numerous times in the past 200 years. However, as is the situation with many of the 129 active volcanoes in Indonesia, thousands of residents still to live on its fertile slopes.

Semeru’s last major eruption was in December 2021, when 51 individuals were killed and several hundred more were burned and villages were buried in thick mud. The event forced the relocation of more than 10,000 people from their houses.

The country, an archipelago of over 280 million people, sits along the Pacific “ring of fire”, a curved series of tectonic boundaries, and is prone to seismic events and volcanism.