Report on Krakatau (Indonesia) — 4 January-10 January 2023
Smithsonian Institution / US Geological Survey
Weekly Volcanic Activity Report, 4 January-10 January 2023
Managing Editor: Sally Sennert.
Please cite this report as:
Global Volcanism Program, 2023. Report on Krakatau (Indonesia) (Sennert, S, ed.). Weekly Volcanic Activity Report, 4 January-10 January 2023. Smithsonian Institution and US Geological Survey.
6.1009°S, 105.4233°E; summit elev. 285 m
All times are local (unless otherwise noted)
PVMBG reported that the eruption at Anak Krakatau continued. A dense gray ash plume was seen at 1410 on 4 January rising 100 m above the summit and drifting E, followed at 1509 by a dense gray-to-black ash plume to 3 km above summit that also drifted E. Another event at 0013 on 5 January sent a dense gray ash plume 750 m above the summit that drifted NE. Although weather sometimes prevented visual observations during 6-9 January, white plumes of variable intensities rose as high as 200 m from the summit and drifted mainly NE and E. 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.
Geological Summary. The renowned Krakatau (frequently mis-named 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.