Report on Krakatau (Indonesia) — 25 September-1 October 2019
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 25 September-1 October 2019
Managing Editor: Sally Kuhn Sennert
Please cite this report as:
Global Volcanism Program, 2019. Report on Krakatau (Indonesia). In: Sennert, S K (ed.), Weekly Volcanic Activity Report, 25 September-1 October 2019. 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 Anak Krakatau’s seismic network recorded 10 eruptive events during 23-29 September. A webcam at the summit recorded diffuse white plumes rising as high as 150 m from the vent at the bottom of the crater. Eruptive events recorded by the webcam at 0813 on 25 September, 0555 and 0835 on 26 September, and 1520 on 27 September generated dense gray-and-white ash plumes that rose 150-200 m from the vent and generally drifted N. The Alert Level remained at 2 (on a scale of 1-4), and the public was warned to remain outside of the 2-km-radius hazard zone from the crater.
Geologic Background. The renowned volcano Krakatau (frequently misstated as Krakatoa) lies in the Sunda Strait between Java and Sumatra. Collapse of the ancestral Krakatau edifice, perhaps in 416 or 535 CE, formed a 7-km-wide caldera. Remnants of this ancestral 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, the 2nd largest in Indonesia during historical time, caused more than 36,000 fatalities, most as a result of devastating 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.