Mount Anak Krakatau Alert Level Lowered After Activity Declines Amid Natural Disasters
Indonesia's Geological Agency lowered the alert level of Mount Anak Krakatau from Level III (Siaga) to Level II (Waspada) on 21 September 2026 after its volcanic activity showed a declining trend following a period of increased eruptions amid natural disasters. [1]
Status Downgrade of Mount Anak Krakatau
The downgrade took effect at 18:30 WIB on 21 September 2026 after comprehensive monitoring showed decreasing seismicity, a 25-hour continuous eruption ending on 6 September, and deflation in deformation data. [1] The decision followed analysis and evaluation of the volcano's current condition by the Head of the Geological Agency Lana Saria. [1] The agency determined the change based on results from thorough monitoring and evaluation. [2] This adjustment occurred after the volcano had been at Level III since 2 July 2026 at 16:30 WIB. [3]
Timeline of Recent Eruptive Activity
During the Level III period that began 2 July 2026, the volcano produced 224 eruptions by 3 September 2026 and lava flows directed northwest, west, and southwest. [1] The period of heightened activity included 224 eruptions through 3 September 2026 while at Level III status. [2] Continuous eruptions lasted about 25 hours from 4 September 2026 at 23:07 WIB until 6 September 2026 at 00:04 WIB. [3] Satellite imagery confirmed lava flows moved northwest, west, and southwest from the eruption center during that time. [2] Activity showed a declining trend after the continuous eruptions ended and through 20 September 2026 at 00:00 WIB, even as seven Strombolian eruptions still occurred. [2]
Mount Anak Krakatau volcano in Indonesia lowered from alert Level III to Level II on 21 September 2026. — Source: gdelt
Monitoring Data and Observations
Satellite and seismic data on 20 September recorded one low-frequency earthquake and continuous tremor with an average amplitude of 2 mm, supporting the assessment of reduced activity. [1] Deformation data indicated deflation as a symptom of decreasing volcanic activity. [2] On 20 September 2026 the seismic records showed one low-frequency earthquake along with continuous tremor averaging 2 mm in amplitude. [3] Volcanic ash from the earlier eruptions reached parts of West Java and West Sumatra. [2]
Current Safety Recommendations
A safety radius of 2 km from the crater remains in effect, barring entry by residents, tourists, and hikers, with warnings for incandescent rock ejections and heavy ashfall. [1] Communities around the volcano along with visitors, tourists, and hikers are prohibited from entering or conducting activities inside the 2 km radius from the center of activity. [3] The agency urged increased vigilance against potential incandescent rock ejections and heavy ashfall. [1] Coastal communities in Banten and Lampung have been told to ignore rumors linking the activity to a potential tsunami, as confirmed by BRIN that no wave anomalies were detected. [3]
Context from Related Developments
The National Research and Innovation Agency confirmed there were no wave anomalies indicating a tsunami in the Sunda Strait. [3] Monitoring of Mount Anak Krakatau activity will continue, with the activity level to be re-evaluated periodically or if significant changes occur. [1] The Level II status and safety recommendations remain in effect until the next evaluation results are issued. [1] The safe radius represents a one-kilometer reduction from the previous Level III status. [2]
Broader Global Volcanic Activity Snapshot
Satellite and seismic data on 20 September recorded one low-frequency earthquake and continuous tremor with an average amplitude of 2 mm, supporting the assessment of reduced activity in the setting of natural disasters. [1] On 20 September 2026 the seismic records showed one low-frequency earthquake along with continuous tremor averaging 2 mm in amplitude. [3] Deformation data indicated deflation as a symptom of decreasing volcanic activity. [2] Volcanic ash from the earlier eruptions reached parts of West Java and West Sumatra. [2]
What to watch next: The level of Mount Anak Krakatau's volcanic activity will be periodically re-evaluated, or if there are significant changes in activity. [2]
