PVMBG reported that, during infrequent times of clear weather during 1 February-21 May, gray and gray-to-brown plumes were observed rising as high as 300 m above Raung's crater rim. Rumbling was frequently heard at the observation post. Crater incandescence was observed during February and on 12 April. Seismicity fluctuated and was dominated by tremor. The Alert Level remained at 2 (on a scale of 1-4); residents and tourists were reminded not to approach the craters within a 2-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.

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