PVMBG reported that multiple dense ash plumes were visible rising above Krakatau’s summit during 8-11 June. On 8 June at 0746 a gray ash plume rose 500 m and drifted SW, and at 1537 a dark-gray ash plume rose 1 km and drifted SW. At 0746 on 9 June gray plume rose 800 m and drifted SW; a dark gray ash plume at 0846 rose 3 km and drifted SW. At 0423, 1431, and 1750 on 10 June gray ash plumes rose 1.5-3.5 km and drifted NW. A webcam image showed incandescent material being ejected above the crater at 0455. At 0030 on 11 June a dense gray ash plume rose 2 km and drifted NW. A webcam image about a half an hour later, at 0102, showed incandescent material being ejected above the crater. Diffuse white gas-and-steam plumes rose just 50 m during 12-13 June. The Alert Level remained at 3 (on a scale of 1-4), and the public was warned to stay at least 5 km away from the crater.

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.

Source: Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as CVGHM)