PVMBG reported that eruptive activity continued at Krakatau during 29 November-5 December. The seismic network recorded eruption events, low-frequency earthquakes, hybrid earthquakes, volcanic earthquakes, harmonic tremor events, and continuous tremor events almost daily. During 29 November-1 December, white and gray plumes rose as high as 300 m above the vent. Volcano Observatory Notices for Aviation (VONAs) and Volcanic Eruption Notices (VENs) were issued during 2-5 December. Incandescent ejecta often accompanied the eruptive events. Eruptions described in three VONAs on 2 December produced dense ash plumes that rose 500-800 m above the vent and drifted NE and NW. On 3 December, six VONAs were issued for eruptions that produced dense gray-to-black and black ash plumes that rose 600-1500 m above the vent and drifted W and NW. Eleven VONAs were issued on 4 December for eruptions that produced dense black ash plumes that rose 700-2,000 m above the vent and drifted SE and NW. Another eight VONAs and VENs were issued during 5 December for eruptions that produced dense gray-to-black and black ash plumes that rose 500-1,500 m above the vent and drifted NW. The Alert Level remained at 3 (on a scale of 1-4), and the public was warned to stay at least 5 km away from the crater in all directions.

Source: Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as CVGHM)

Geological Summary. The renowned Krakatau (frequently misnamed as Krakatoa) volcano lies in the Sunda Strait between Java and Sumatra. Collapse of an older edifice, perhaps in 416 or 535 CE, formed a 7-km-wide caldera. Remnants of that volcano are preserved in Verlaten and Lang Islands; subsequently the Rakata, Danan, and Perbuwatan cones were formed, coalescing to create the pre-1883 Krakatau Island. Caldera collapse during the catastrophic 1883 eruption destroyed Danan and Perbuwatan, and left only a remnant of Rakata. This eruption caused more than 36,000 fatalities, most as a result of tsunamis that swept the adjacent coastlines of Sumatra and Java. Pyroclastic surges traveled 40 km across the Sunda Strait and reached the Sumatra coast. After a quiescence of less than a half century, the post-collapse cone of Anak Krakatau (Child of Krakatau) was constructed within the 1883 caldera at a point between the former Danan and Perbuwatan cones. Anak Krakatau has been the site of frequent eruptions since 1927.