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Report on Krakatau (Indonesia) — July 2003


Krakatau

Bulletin of the Global Volcanism Network, vol. 28, no. 7 (July 2003)
Managing Editor: Edward Venzke.

Krakatau (Indonesia) Foggy weather and low seismicity

Please cite this report as:

Global Volcanism Program, 2003. Report on Krakatau (Indonesia) (Venzke, E., ed.). Bulletin of the Global Volcanism Network, 28:7. Smithsonian Institution. https://doi.org/10.5479/si.GVP.BGVN200307-262000



Krakatau

Indonesia

6.102°S, 105.423°E; summit elev. 155 m

All times are local (unless otherwise noted)


According to reports from the Volcanological Survey of Indonesia (VSI), no visual observations were made this month due to foggy weather. The volcano remained at alert level 2 for the month. They also noted that relatively few volcanic and tectonic earthquakes were recorded during the weeks of 2-8 and 9-15 June 2003. Specifically, the 2-8 June record consisted of 9 deep volcanic earthquakes, 19 shallow volcanic earthquakes, and 5 tectonic earthquakes; the record of 9-15 June consisted of 6 deep volcanic earthquakes, 17 shallow volcanic earthquakes, and 4 tectonic earthquakes.

In the week of 16-22 June, a significant increase in shallow volcanic earthquakes was observed, although no tectonic earthquakes were recorded. The sesimic record for that week showed 11 deep volcanic earthquakes and 63 shallow volcanic earthquakes. Both volcanic and tectonic earthquakes were recorded for the week of 23-29 June, with 7 deep volcanic earthquakes, 61 shallow volcanic earthquakes, and 2 tectonic earthquakes detected.

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.

Information Contacts: Dali Ahmad and Nia Haerani, Volcanological Survey of Indonesia (VSI), Jalan Diponegoro No. 57, Bandung 40122, Indonesia (URL: http://www.vsi.esdm.go.id/).