Indonesian authorities have raised the alert level for Slamet volcano in Central Java from 1 to 2 on August 9, 2019. The last eruption of this volcano took place in 2014.
The Center for Volcanology and Disaster Mitigation (PVMBG) raised the status of the volcano due to a significant increase in seismic activity and deformation. There are still no visually signs of eruption, the center said.
The current potential threat is a magmatic eruption with incandescent material possible within a 2 km (1.2 miles) radius, or phreatic eruption and ash around a potential crater. Both can happen without further precursors.
The volcano had numerous VEI 1 and 2 eruptions since 1772.
Slamet, Java's second-highest volcano at 3 428 m (11 246 feet) and one of its most active, has a cluster of about three dozen cinder cones on its lower SE-NE flanks and a single cinder cone on the western flank.
It is composed of two overlapping edifices, an older basaltic-andesite to andesitic volcano on the west and a younger basaltic to basaltic-andesite one on the east. Gunung Malang II cinder cone on the upper E flank on the younger edifice fed a lava flow that extends 6 km (3.7 miles) E.
Four craters occur at the summit of Gunung Slamet, with activity migrating to the SW over time.
Historical eruptions, recorded since the 18th century, have originated from a 150-m-deep (492 feet), 450-m-wide (1 476 feet), steep-walled crater at the western part of the summit and have consisted of explosive eruptions generally lasting a few days to a few weeks.
Featured image: Mount Slamet, Central Java, Indonesia - 2011 (public domain)