Report on Krakatau (Indonesia) — 25 January-31 January 2023
Smithsonian Institution / US Geological Survey
Weekly Volcanic Activity Report, 25 January-31 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, 25 January-31 January 2023. Smithsonian Institution and US Geological Survey.
6.102°S, 105.423°E; summit elev. 155 m
All times are local (unless otherwise noted)
PVMBG reported that the eruption at Anak Krakatau continued during 24-31 January. Eruptive events at 0231 and 2256 on 25 January and 0003 on 26 January ejected incandescent material from the vent, based on webcam photos. Eruptive events at 0512, 0633, and 0732 on 26 January and 1312 on 27 January produced dense gray ash plumes that rose 300-500 m above the summit and drifted NE, E, and SE. Webcam images showed incandescent ejecta at 2135, 2144, and 2328 January. 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 volcano Krakatau (frequently misstated as Krakatoa) lies in the Sunda Strait between Java and Sumatra. Collapse of the ancestral 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 Rakata, Danan, and Perbuwatan volcanoes 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 cones of Danan and Perbuwatan. Anak Krakatau has been the site of frequent eruptions since 1927.