A brown-gray ash plume from Raung rose 100-400 m above the crater rim and drifted E at 0520 on 21 January, prompting PVMBG to raise the Alert Level to 2 (on a scale of 1-4). Gray plumes rose 200-600 m above the crater rim and drifted E on the next day. White-and-gray plumes rose 200-500 m on 23 January and drifted WSW, and crater incandescence was visible in webcam images. During 24-25 January ash plumes rose 500 m and drifted E and S, and Strombolian activity was visible.

Geological Summary. Raung, one of Java's most active volcanoes, is a massive stratovolcano in easternmost Java that was constructed SW of the rim of Ijen caldera. The unvegetated summit is truncated by a dramatic steep-walled, 2-km-wide caldera that has been the site of frequent historical eruptions. A prehistoric collapse of Gunung Gadung on the W flank produced a large debris avalanche that traveled 79 km, reaching nearly to the Indian Ocean. Raung contains several centers constructed along a NE-SW line, with Gunung Suket and Gunung Gadung stratovolcanoes being located to the NE and W, respectively.

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