The Indonesian Geological Agency reported that Semeru, the highest mountain on the island of Java, unleashed pyroclastic flows of hot ash, a mix of rocks, lava, and gas that traveled up to 7 kilometers (4.3 miles) down its slopes. The column of hot clouds rose 2 kilometers (1.2 miles) into the air. The expulsion of gases and volcanic rocks throughout the day forced authorities to raise the volcano's alert level twice, from the third-highest level to the highest. A video recorded by a security camera showed the spectacular and violent start of the eruption.
Although no casualties have been reported, more than 300 residents from the three most at-risk villages in the Lumajang district were evacuated to government shelters. The National Disaster Mitigation Agency spokesperson, Abdul Muhari, noted that the increasing volcanic activity led authorities to expand the danger zone to 8 kilometers (5 miles) from the crater. Residents have been advised to stay away from the Besuk Kobokan River as it is the path of the lava flow.
Social media videos showed residents fleeing to temporary shelters, some with faces covered in volcanic dust.
Local media also reported that authorities were coordinating the rescue of about 178 people stranded on the mountain, including a group of 137 climbers. However, a spokesperson for the Bromo-Tengger-Semeru National Park (TNBTS) assured that the group is "currently safe" at the Ranu Kumbolo monitoring post, located outside the path of the hot cloud flow.
Semeru, also known as Mahameru, has erupted numerous times in the last 200 years. Its last major eruption in December 2021 left 51 people dead and forced the relocation of nearly 3,000 homes. Indonesia is located in the Pacific "Ring of Fire," making it prone to this type of volcanic activity.