Mount Semeru Erupts, Spewing Ash 1 Km Above Summit

Mount Semeru, located on the border of Lumajang and Malang regencies in East Java, erupted on Monday morning, with the height of the eruption reaching 1 kilometre above the summit. “The eruption of Mount Semeru occurred at 05.13 WIB. The observed height of the eruption column was approximately 1 kilometre above the peak, or 4,676 metres above sea level,” said Mount Semeru Observation Post Officer Yadi Yuliandi in a written report received in Lumajang. According to him, the ash column was observed to be grey with thick intensity moving northwards, and the eruption was recorded on a seismograph with a maximum amplitude of 22 mm and a duration of 167 seconds. He explained that the volcanic activity of Mount Semeru is currently at Status Level III (Alert), with a recommendation that the public not conduct any activities in the southeast sector along Besuk Kobokan as far as 13 kilometres from the summit. Beyond that distance, he continued, the public should not conduct activities within 500 metres of the riverbank along Besuk Kobokan due to the potential for being affected by the expansion of pyroclastic flows and lava flows up to a distance of 17 kilometres from the summit. “The public is prohibited from conducting activities within a five-kilometre radius of the crater/peak of Mount Semeru, as it is prone to the danger of ejected incandescent rocks,” he said. He urged the public to be aware of the potential for pyroclastic flows, lava avalanches, and lahars along the river channels and valleys originating at the peak of Mount Semeru, particularly along Besuk Kobokan, Besuk Bang, Besuk Kembar, and Besuk Sat, as well as the potential for lahars in small streams that are tributaries of Besuk Kobokan. Meanwhile, the Lumajang Regency Government reminded the public, especially sand miners, to increase their vigilance against the danger of secondary explosions from Mount Semeru’s volcanic material in lahar flow areas and mining zones. Lumajang Regent Indah Amperawati stated that the threats around an active volcano do not only come from eruptions or pyroclastic flows, but also from accumulations of volcanic material that still retain heat. Material carried from the slopes of Mount Semeru can maintain high temperatures for a certain period, and these material deposits have the potential to trigger secondary explosions that endanger people working too close, especially in mining areas. “Never assume that material deposits in the Semeru area are completely safe. The material could still be hot and, under certain conditions, pose a danger to the public, particularly miners,” she said. According to her, understanding the hazardous characteristics of volcanic material is very important, especially for residents who work daily around the Besuk Kobokan flow and other mining areas. “Material that appears dormant or has settled is not necessarily completely safe to approach or mine,” she said. She added that the risk in the Semeru area can also increase when rain falls on the summit and slopes of the mountain. Rainwater can mobilise material stored in river channels, thereby increasing the potential danger for people working around lahar paths and mining areas. “The public is urged not only to pay attention to information about eruptions or pyroclastic flows, but also to understand the risks from residual volcanic material from eruptions that remains along river channels and mining areas,” she said.