Report on Krakatau (Indonesia) — February 1999
Bulletin of the Global Volcanism Network, vol. 24, no. 2 (February 1999)
Managing Editor: Richard Wunderman.
Krakatau (Indonesia) Sporadic ash eruptions in February and March 1999
Please cite this report as:
Global Volcanism Program, 1999. Report on Krakatau (Indonesia) (Wunderman, R., ed.). Bulletin of the Global Volcanism Network, 24:2. Smithsonian Institution. https://doi.org/10.5479/si.GVP.BGVN199902-262000.
6.102°S, 105.423°E; summit elev. 155 m
All times are local (unless otherwise noted)
Krakatau erupted on 5 February 1999 accompanied by thunderclaps and an ash plume that reached a height of ~1,000 m above the summit. The activity continued until 10 February with ash plumes reaching ~100-300 m above the summit. The continuing sporadic eruptions deposited small amounts of ash over most of the island; a deposit of ~0.3 mm was measured near the observatory. On 11 February, the glow of ejecta was observed reaching ~25 m above the summit and continued during the night.
Activity decreased early during the week of 9-15 March. Weak booming noises were heard twice on 9 and 10 March, but plumes were not observed. At the end of the week booming noises were rare, and a white-gray ash plume was seen on 14 March that rose 100-300 m above the summit. The current activity is a continuation of eruptions that began in 1992.
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.
Information Contacts: R. Sukhyar and Dali Ahmad, Volcanological Survey of Indonesia (VSI), Jalan Diponegoro No. 57, Bandung 40122, Indonesia (URL: http://www.vsi.esdm.go.id/).