Report on Krakatau (Indonesia) — May 1999
Bulletin of the Global Volcanism Network, vol. 24, no. 5 (May 1999)
Managing Editor: Richard Wunderman.
Krakatau (Indonesia) Occasional explosions producing ash columns
Please cite this report as:
Global Volcanism Program, 1999. Report on Krakatau (Indonesia) (Wunderman, R., ed.). Bulletin of the Global Volcanism Network, 24:5. Smithsonian Institution. https://doi.org/10.5479/si.GVP.BGVN199905-262000.
6.102°S, 105.423°E; summit elev. 155 m
All times are local (unless otherwise noted)
Following several months of intense activity that began on 5 February (BGVN 24:04), Anak Krakatau became relatively quiet in late April. From the end of April until the end of May, only several explosions were heard. On 26 April a weak explosion sent a white-gray ash plume 200-500 m high. Between 4 and 17 May there were two blasts per week, each accompanied by a glow and white-gray ash reaching between 100 and 400 m high. In the week from 18 to 24 May, in addition to two explosions, a shock on the morning of 20 May registered at 2 on the MMI scale.
Anak Krakatau was very active from 1992 to 1997, depositing 6.8 x 106 m3 of lava flows. The island was enlarged by 378,527 m2 and the height of the cone increased from 159 to ~300 m.
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: Volcanological Survey of Indonesia (VSI), Jalan Diponegoro No. 57, Bandung 40122, Indonesia (URL: http://www.vsi.esdm.go.id/).