Anak Krakatau Expands to 341.5 Hectares from Eruptive Deposits Amid Natural Disasters
Anak Krakatau in Indonesia has expanded to 341.5 hectares due to ongoing eruptions and accumulation of volcanic deposits, surpassing its pre-2018 collapse size, while two new island-like landforms have been detected nearby and a rare blue fire phenomenon appeared at Mount Papandayan amid natural disasters. Sentinel satellite imagery from Sept. 15 confirmed that volcanic deposits continuously expanded the Sunda Strait island beyond the 300 hectares recorded just days before the 2018 landslide and deadly tsunami. [1]
Anak Krakatau Land Expansion
Mount Anak Krakatau’s land area has expanded to 341.5 hectares following ongoing eruptions, surpassing its size prior to its catastrophic December 2018 collapse, according to official geological monitoring data. [1] PVMBG recorded the area at 312.3 hectares on Aug. 8, before an additional 32.8 hectares of eruptive material deposited in early September brought the total to 341.5 hectares. [1] Satellite imagery also showed the volcano itself has grown by nearly 33 hectares. [2] Apart from the two formations, the satellite imagery also showed Anak Krakatau itself had gained about 32.8 hectares of land in its northwest, west and southwest sectors due to deposits of pyroclastic material and lava flows from the same eruptions. [2]
2018 Collapse and Reconstruction Phase
The collapse of the volcano's southwestern flank drastically reduced its landmass to 246.18 hectares by late December 2018, according to the Center for Volcanology and Geological Hazard Mitigation (PVMBG). [1] "The collapse of the southwestern sector drastically reduced the mountain's land area to just 246.18 hectares by Dec. 26, 2018," PVMBG Head Rita Susilawati said in a statement on Saturday. [1] BRIN researcher Dini Nurfiani noted that the 2018 collapse displaced roughly 0.116 cubic kilometers of material into the ocean, reducing the summit elevation from 330 meters to 120 meters. [1] While immediate post-collapse eruptions were explosive Surtseyan events triggered by seawater entering the crater, activity later transitioned between 2019 and 2026 to Strombolian lava fountaining and flows, steadily accumulating landmass. [1]
Satellite image shows Anak Krakatau expanded to 341.5 hectares from volcanic deposits. — Source: gdelt
Detection of New Island-like Landforms
Two small island-like landforms have appeared near Anak Krakatau in the Sunda Strait after about 25 hours of continuous eruptions earlier this month. [2] Centre for Volcanology and Geological Hazard Mitigation (PVMBG) head Siti Sumilah Rita Susilawati said Sentinel satellite imagery showed the two landforms northwest and southeast of Anak Krakatau, which were believed to be linked to continuous eruptive activity from Sept 4 to 6. [2] "Our preliminary interpretation is that fluid magma released during the continuous eruption reached the surface through an opening extending from northwest to southeast, causing eruptive material to form land at other locations that appeared as two island-like mounds,” she said in a statement on Friday. [2] Badan Geologi also detected two gumuk or small land protrusions around the body of Anak Krakatau located in the northwest and southeast parts of the volcano. [3] However, the existence of the two gumuk has not been confirmed as islands or new volcanoes. [3]
Blue Fire Phenomenon at Mount Papandayan
Indonesian geological authorities have deployed an emergency team to evaluate potential hazards following reports of a rare blue fire phenomenon inside the active crater of Mount Papandayan in West Java. [4] Head of the Center for Volcanology and Geological Hazard Mitigation (PVMBG) Rita Susilawati said on Friday that visual observations on Sept. 23 recorded purplish-blue flames glowing across several sections of the crater. [4] By Sept. 24, the fires had diminished into a more concentrated, whitish-blue glow. [4] "The Geological Agency team is currently conducting a field inspection to analyze this phenomenon and its potential danger," Susilawati said. [4] Experts attribute the display to the natural combustion of sulfur gases escaping through solfatara vents—a process previously documented near the volcano's newer crater area. [4]
Current Alert Levels and Safety Recommendations
Anak Krakatau’s alert status was lowered on Sept 21 from Level III, the second-highest level in Indonesia's four-tier volcano alert system, to Level II following a decline in volcanic activity. [2] Under the current alert level, Siti Sumilah urged the public to remain calm and stay at least two kilometres from the eruption centre and one kilometre from the two newly detected formations. [2] Despite the unusual activity, officials confirmed Mount Papandayan’s alert status remains unchanged at Level I (Normal). [4] Authorities have urged the public, tourists, and hikers to stay calm but maintain a safe distance, advising against any activity or overnight stays within 500 meters of the active crater rim. [4]
Scientific Monitoring and Structural Concerns
Joint research by Indonesia's National Research and Innovation Agency (BRIN) and international partners—including the University of Birmingham, Institut Teknologi Bandung, Penn State University, the British Geological Survey, and the University of Oxford—confirmed the volcano is in an active reconstruction phase. [1] However, scientists warn that the volcano’s regrowth remains structurally asymmetrical. [1] The southwestern flank is building over a steep underwater caldera slope, while the northeastern side sits on a shallower seabed. [1] Dense lava layers piling atop light, porous ash deposits on uneven slopes continue to pose risks for long-term slope stability. [1]
What to watch next: Regular satellite observations allow tracking of natural hazard development in places like Kamchatka where the NISAR mission captured lava flows from Krasheninnikov volcano filling an inner caldera before overflowing into a wider crater. [5]
