The southwest dome of the change in changes due to the addition of lava volume, BPPTKG set the status of Mount Merapi Alert

YOGYAKARTA – Volcanic activity of Mount Merapi still shows an increase. The Head of the Geological Disaster Technology Investigation and Development Center (BPPTKG), Agus Budi Santoso, said that the southwest lava dome experienced morphological changes due to the addition of the volume and intensity of the lava fall.

BPPTKG released an official report on the activity of Mount Merapi for 6 to 12 June 2025. In the report, officers recorded various visual phenomena, seismicity, deformation, and potential hazards that continued to increase.

The observer team noted the weather around Mount Merapi is generally bright in the morning and evening, even though afternoon to evening tends to be foggy.

In these conditions, officers managed to observe white smoke from the summit of Mount Merapi, with weak pressure and height varies between 10 meters to 475 meters.

“Mount Merapi also continues to launch a lava fall,” he said, Saturday (6/14/2025)

Lava dome conditions

In the past week, observations recorded 19 lava falls leading to the upstream of the Krasak River as far as a maximum of 1,800 meters, 27 times to the upper Kali Bebeng as far as a maximum of 2,000 meters, and 18 times to the upstream of the Sat/White River as far as a maximum of 2,000 meters.

Based on visual analysis of the camera station ngepos and Babadan2, officers detect changes in the morphology of the southwest lava dome.

Agus Budi Santoso explained that the changes occurred due to the activity of falling and the addition of the volume of lava material. Meanwhile, the middle dome does not show morphological changes.

Aerial photographs on May 30, 2025 showed that the volume of the southwest dome had reached 4,049,300 cubic meters, while the middle dome has a volume of around 2,367,300 cubic meters.

In the same period, the team recorded an increase in seismic intensity. Seismic networks around Mount Merapi recorded 39 times the shallow volcanic earthquake (VTB), 927 times the large phase (MP) earthquake, 1 Low Frequency (LF), 584 earthquake (RF), and 19 tectonic (TT) earthquakes. This number shows a significant increase compared to the previous week.

Agus Budi Santoso asserted that this data strengthened indications that the supply of magma to the surface is still ongoing, which has the potential to trigger hot clouds.

The results of deformation monitoring using EDM and GPS showed that the distance of the tuft did not experience significant changes. EDM measurements from the fixed point of the Babo to the RB2 and RB3 reflectors show stability, as well as the GPS baseline data between Labuhan and Jrakah.

“Although deformation is monitored stable, BPPTKG still emphasizes that volcanic activity is still high and potential danger remains,” he said.

The rain had fallen around the Mount Merapi observation post with the highest intensity recorded at the Babadan Post on June 9, 2025 of 40 mm/hour for 51 minutes. However, there were no reports of new lava flows in rivers that were bumped in Merapi.

Mount Merapi Status Alert

Agus Budi Santoso concluded that the activity of Mount Merapi is still relatively high in the form of effusive eruption. Therefore, BPPTKG determines the status of Merapi’s activity at the “API” level.

The current potential hazards include the following conditions.

• Lava and hot clouds in the southern sector – Barat Daya: Boyong River (a maximum of 5 km), Bedog, Krasak, and Bebeng River (a maximum of 7 km).
• Southeast Sector: River Woro (maximum 3 km) and River Gendol (maximum 5 km).

The volcanic material from the explosive eruption can reach a radius of up to 3 km from the peak.

BPPTKG issued strict recommendations to stakeholders and the community:

The Government of Sleman Regency, Magelang, Boyolali, and Klaten was asked to immediately increase the capacity of mitigation and prepare evacuation facilities.

The community needs to be aware of the threat of lava and hot clouds, especially when it rains in the Merapi area.
The community is advised to anticipate interference due to volcanic ash.

If the activity of Mount Merapi experiences significant changes, BPPTKG will immediately review the level of activity status. (EF Linangkung)