A thick white plume reached 25 m above the summit several times during October through December 2001. During 27 August 2001 through 16 September 2001 at Krakatau, available seismic data were dominated by explosions and shallow volcanic earthquakes (table 1). The seismograph broke on 16 September 2001 but was repaired by 26 August 2002, when it showed a slight increase over the previous interval when data were available. No surface activity accompanied the increased seismicity. Volcanic events decreased during early September. The volcano remained at Alert Level 2 through at least 8 September.

Table 1. Earthquakes registered at Krakatau during 27 August 2001 through 8 September 2002. The seismic system was down during 16 September 2001-25 August 2002. Courtesy of VSI.

Geological Summary. The renowned Krakatau (frequently mis-named as Krakatoa) volcano lies in the Sunda Strait between Java and Sumatra. Collapse of an older 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 the Rakata, Danan, and Perbuwatan cones 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 Danan and Perbuwatan cones. Anak Krakatau has been the site of frequent eruptions since 1927.

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