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Report on Krakatau (Indonesia) — July 1979


Krakatau

Scientific Event Alert Network Bulletin, vol. 4, no. 7 (July 1979)
Managing Editor: David Squires.

Krakatau (Indonesia) Tephra and lava flow from 1978 crater

Please cite this report as:

Global Volcanism Program, 1979. Report on Krakatau (Indonesia) (Squires, D., ed.). Scientific Event Alert Network Bulletin, 4:7. Smithsonian Institution. https://doi.org/10.5479/si.GVP.SEAN197907-262000



Krakatau

Indonesia

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

All times are local (unless otherwise noted)


Activity from Anak Krakatau's 100-m-diameter 1978 crater resumed in mid-July. Bombs (average diameter 1 m), lapilli, and ash were ejected every 5-15 minutes, rising 200 m and covering the area within about 700 m of the crater. Lava flowed W, reaching the coast about 450 m away. A danger zone has been delineated within 3 km of the crater.

The 1979 eruption is stronger than that of 1978, when ash and lapilli were ejected, but no bombs or lava flows.

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: A. Sudradjat, VSI.