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.

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

Geological Summary. The renowned Krakatau (frequently misnamed 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.