CVGHM reported that seismicity from Ibu increased during 6-14 April and remained elevated during 15-20 April. Plumes described as “eruption smoke” rose to altitude of 1.8-2.1 km (5,900-6,900 ft) a.s.l. during 12-21 April and were gray during 18-21 April. The Alert Level was increased to 3 (on a scale of 1-4) on 21 April. Residents and tourists were not permitted within 2 km of the crater.
Source: Center of Volcanology and Geological Hazard Mitigation (CVGHM) – “Reports provided courtesy of the Smithsonian’s Global Volcanism Program and the US Geological Survey’s Volcano Hazards Program.”