BPPTKG: Two Lava Domes of Mount Merapi Experience Volume Increase

The Geological Disaster Technology Research and Development Agency (BPPTKG) Yogyakarta has reported growth in the volume of two lava domes on Mount Merapi, based on observations conducted over the past week, from Friday (24/7) to Thursday (30/7).

Agus Budi Santosa, Head of BPPTKG Yogyakarta, revealed that the volume of the South-West Dome increased by approximately 2,000 cubic metres, bringing its total volume to 4,021,200 cubic metres. Meanwhile, the Central Dome experienced an addition of about 600 cubic metres, reaching a total volume of 2,369,400 cubic metres.

“Thermal photo analysis shows that the temperature of both domes was measured at 243 degrees Celsius, which is considered relatively stable compared to previous measurements,” Agus stated in an official briefing on Friday (31/7/2026).

During the observation period, Mount Merapi was seen emitting white smoke with varying intensities, ranging from thin to thick, at heights between 10 and 150 metres. Two pyroclastic flows (cloud of hot ash) were also recorded, with a maximum glide distance of 2,000 metres towards the upper reaches of the Boyong and Sat/Putih rivers.

Lava collapse activity also remains intense, with seismic data recording 2 pyroclastic flow earthquakes, 31 shallow volcanic earthquakes, 551 multi-phase earthquakes, 4 low-frequency earthquakes, 647 rockfall earthquakes, and 12 tectonic earthquakes. Despite high volcanic activity, the intensity of seismicity this week was reported to be lower than the previous week.

Based on visual and instrumental observations, BPPTKG concluded that the volcanic activity of Mount Merapi remains at a sufficiently high level, characterised by effusive eruptions. Currently, the activity status of Mount Merapi is set at level ‘SIAGA’ (Alert).

Monitoring data indicates that the magma supply is ongoing, which has the potential to trigger pyroclastic flows within the designated danger zones. The public is urged to remain vigilant and avoid any activities within the danger zones established by the relevant authorities.