PVMBG reported that a phreatic eruption at Merapi began at 0125 on 21 May and lasted for 19 minutes, generating an ash plume that rose 700 m above the crater and drifted W.
A six-minute-long phreatic eruption began at 0938 and produced an ash plume that rose 1.2 km above the crater.
Ashfall from both events was reported in areas 15 km downwind.
A third event, detected at 1750, lasted three minutes and produced a plume of unknown height.
After the events one volcano-tectonic earthquake and one tremor event were recorded.
The seismicity along with increased phreatic events prompted PVMBG to raise the Alert Level to 2 (on a scale of 1-4).
Source: Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as CVGHM)