Based on PVMBG information, and satellite-image and pilot observations, the Darwin VAAC reported that during 15-21 July ash multiple ash plumes from Raung rose to varying altitudes of 3.7-6.1 km (12,000-20,000 ft) a.s.l. and drifted as far as 340 km in multiple directions. On 16 July BNPB reported that a dense gray-to-black ash plume rose as high as 2 km above Raung's crater rim and drifted WNW. Incandescent lava at the summit was visible and tremor was continuous. Roaring and thumping sounds were reported by residents. Ashfall was reported in areas downwind, including Cumedak (19 km W) and Sumberjambe (13 km NW). According to a news article, the Juanda International Airport in Surabaya reopened on 17 July after on-and-off closures the previous week. BNPB noted that the eruption continued on 18 July with ash plumes rising as high as 1.5 km and drifting N. Tremor continued, although the amplitude had declined during the previous week. The Alert Level remained at 3 (on a scale of 1-4), and the public was reminded not to approach the crater within a 3-km radius.

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.

Sources: Badan Nacional Penanggulangan Bencana (BNPB), Darwin Volcanic Ash Advisory Centre (VAAC), ch-aviation