On 4 August BNPB reported that during the previous three days the Strombolian eruption at Raung increased in intensity. Ash fell in Sempu, Songgon, Glenmore, Gambiran, and Banyuwangi. On 4 August dense blackish gray ash plumes rose 800 m and drifted SE. Based on satellite-image and wind data, the Darwin VAAC reported that during 29 July-4 August multiple ash plumes rose to altitudes of 4.3-4.9 km (14,000-16,000 ft) a.s.l. and drifted as far as 240 km in multiple directions. 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)