CVGHM reported that on 28 March gas emissions continued to be elevated at Timbang, a cone that is part of the Dieng Volcanic Complex. Plumes containing carbon dioxide drifted 2 km towards the S valley of Kali Sat, prompting a road closure until the early evening when the gas concentration decreased. On 30 March carbon dioxide gas emissions were not detected; however, "smoke" rose at most 100 m above the crater. Hydrogen sulfide odors were very potent in areas 1 km W and weak in areas 1.5 km S. On 19 April sulfur dioxide odors were reported.

On 24 March Sileri Crater lake water changed from dark gray to brown. On 7 April white plumes rose 50 m and the water color returned to normal. Diffuse white plumes rose 15 m on 20 April. Other craters had not exhibited any changes by 28 April.

Based on gas concentrations, seismicity, and visual observations, CVGHM raised the Alert Level to 3 (on a scale of 1-4) on 8 May and warned the public not to approach Timbang Crater within a 500-m radius.

Geological Summary. The Dieng plateau in the highlands of central Java is renowned both for the variety of its volcanic scenery and as a sacred area housing Java's oldest Hindu temples, dating back to the 9th century CE. The Dieng Volcanic Complex consists of multiple stratovolcanoes and more than 20 small Pleistocene-to-Holocene craters and cones over a 6 x 14 km area. Prahu stratovolcano was truncated by a large Pleistocene caldera, which was subsequently filled by a series of cones, lava domes, and craters, many containing lakes. Lava flows cover much of the plateau, but observed activity has been restricted to minor phreatic eruptions. Gas emissions are a hazard at several craters and have caused fatalities. There are abundant thermal features and high heat flow across the area.

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