Report on Krakatau (Indonesia) — 20 March-26 March 2019
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 20 March-26 March 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, 20 March-26 March 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 a total of six explosions at Anak Krakatau were recorded on 18 March, with dense white plumes rising as high as 500 m from the summit. During 18-24 March no other plumes were noted although weather conditions often prevented visual observations. Events were recorded at 0301 and 0305 on 24 March, though ash plumes were not visible. The Alert Level remained at 3 (on a scale of 1-4), and residents were warned to remain outside of the 5-km radius hazard zone from the crater. [Correction: the Alert Level was lowered to 2 on 25 March, and the hazard zone was adjusted to a 2-km radius.]
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.