Merapi volcano (Central Java, Indonesia) - Smithsonian / USGS Weekly Volcanic Activity Report for 15 December-21 December 2021 (Continuing Activity)

BPPTKG reported no significant morphological changes at Merapi's lava domes, located just below the SW rim and in the summit crater, during 10-16 December. The estimated dome volumes were almost 1.63 million cubic meters for the SW dome and just over 3 million cubic meters for the summit dome. The intensity of the seismic signals remained at high levels.
As many as 116 lava avalanches traveled a maximum of 2 km SW down the Bebeng drainage, and three pyroclastic flows traveled a maximum of 2.2 km SW. At 1643 on 18 December a pyroclastic flow advanced 2 km SW and produced an ash plume that rose 400 m. The Alert Level remained at 3 (on a scale of 1-4), and the public was warned to stay 3-5 km away from the summit based on location.

Source: Balai Penyelidikan dan Pengembangan Teknologi Kebencanaan Geologi (BPPTKG)
---
From: Global Volcanism Program, 2021. Report on Merapi. In: Mayberry, G (ed.), Weekly Volcanic Activity Report 15 December-21 December 2021. Smithsonian Institution and US Geological Survey.