Report on Krakatau (Indonesia) — 25 December-31 December 2019
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 25 December-31 December 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 December-31 December 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 on 29 December an eruption at Anak Krakatau recorded by the webcam generated an ash plume that rose 200 m above the vent and drifted N. According to Simon Carn, satellite images of the volcano acquired by Planet Labs on 30 December suggested that the crater lake was almost gone, replaced by tephra deposits and a growing cone. PVMBG noted that during 30-31 December seismicity increased, minor inflation was recorded, and eruption plumes rose as high as 2 km above the summit (about 157 m a.s.l.). An eruption at 0651 on 31 December produced a dense gray-to-black ash plume that rose around 1 km above the vent and drifted S. 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.