Indonesia cuts Mount Slamet hazard radius to 2 km, alert status unchanged

Indonesia's Mount Slamet has had its recommended hazard radius reduced to 2 kilometers from its crater, though its alert status remains at Level II (Caution). The Center for Volcanology and Geological Hazard Mitigation (PVMBG) made the adjustment after monitoring showed volcanic activity to be high but not significantly increased.

Lana Saria, acting head of the Geological Agency, stated that continuous observations are underway to anticipate any changes. The decision to reduce the radius follows a period where it had been expanded from two to three kilometers due to increased thermal activity and heat anomalies around the crater. These anomalies indicated a rise in thermal activity and an expansion of fracture systems, leading to increased volcanic gas release.

“

Intensive observations continue to be carried out to anticipate changes in activity and potential hazards that may occur.

However, between April 4 and June 3, 2026, no further escalation in thermal activity was observed. Thermal drone measurements showed fluctuating temperatures of the crater's solfatara, ranging from 407.2 to 478.7 degrees Celsius, indicating relatively high but stable thermal activity. Other monitoring indicators also showed fluctuating, though generally decreasing, activities, but the mountain's activity has not yet returned to normal background levels.

Mount Slamet, a stratovolcano standing approximately 3,432 meters high, is administratively located across five regencies in Central Java. The PVMBG urges the public, hikers, and tourists to adhere to the established safety zones.

“

The temperature rise indicates an increase in thermal activity around the crater.