Gunung Anak Krakatau in the Sunda Strait has expanded beyond its pre-2018 collapse dimensions, reaching a total land area of approximately 341.5 hectares following continuous eruptions in September 2026. Sentinel satellite imagery analyzed by the Center for Volcanology and Geological Hazard Mitigation (PVMBG) under the Geological Agency shows the island added 32.8 hectares of material during eruptions that occurred between September 4 and September 6, 2026.
Sunda Strait Volcano Surpasses Pre-2018 Dimensions
Before its destructive flank collapse on December 22, 2018—an event that triggered tsunamis along the coasts of Banten and Lampung—the volcano covered roughly 300 hectares as of December 19, 2018. The 2018 sector collapse and subsequent underwater landslides drastically pruned the landmass down to 246.18 hectares by December 26, 2018, according to Rita Susilawati, Head of PVMBG at the Ministry of Energy and Mineral Resources. Satellite observations from Sentinel taken on September 15, 2026, confirmed that ongoing eruptive activity has built the footprint back past its pre-collapse size to 341.5 hectares.
Rebuilding Phase Confirmed by International Research
The physical expansion aligns with findings from a collaborative research initiative involving the National Research and Innovation Agency (BRIN), the University of Birmingham, the Institut Teknologi Bandung (ITB), Penn State University, the British Geological Survey, and the University of Oxford. Dini Nurfiani, a researcher at BRIN’s Geological Disaster Research Center, stated that the volcano’s evolution demonstrates a recurring geological cycle of growth, eruption, collapse, and reconstruction. The 2018 collapse ejected roughly 0.116 cubic kilometers of material into the sea, reducing the peak’s height from 330 meters to 120 meters and allowing seawater to enter the vent. This shift temporarily altered the eruption style from Strombolian to the more explosive Surtseyan type before activity transitioned back toward Strombolian eruptions, lava fountains, and new lava flows that consistently build up volume.
Asymmetric Growth Dynamics and Long-Term Stability
Researchers emphasize that the expansion of Gunung Anak Krakatau is not uniform. The southwest sector rests atop a steep submarine caldera slope, whereas the northeast section sits on a shallower seabed. This structure—formed by dense, heavy lava resting over weaker, porous tuff deposits on uneven slopes—remains a core factor influencing the long-term stability of the volcano’s flanks. Dini noted that historical eruption behavior shifts over time as the physical body of the volcano, its magma system, and environmental conditions continue to interact.
Related reading