Report on Krakatau (Indonesia) — 14 July-20 July 2004
Smithsonian / US Geological Survey Weekly Volcanic Activity Report,
14 July-20 July 2004
Managing Editor: Gari Mayberry
Please cite this report as:
Global Volcanism Program, 2004. Report on Krakatau (Indonesia). In: Mayberry, G (ed.), Weekly Volcanic Activity Report, 14 July-20 July 2004. Smithsonian Institution and US Geological Survey.
6.102°S, 105.423°E; summit elev. 155 m
All times are local (unless otherwise noted)
In July there was an increase in the number of gas-and-steam emissions from the crater of Anak Krakatau. In addition, the number of volcanic earthquakes increased from 1-4 per day before 5 July, to ~57 per day, then dropped to 2-17 earthquakes per day by mid-July. The Alert Level at Krakatau was raised from 1 to 2 (on a scale of 1-4). Visits to the crater were prohibited.
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.