Mount Merapi Erupts, Launches 2.5 Km Hot Clouds To Boyong River

Solfatara smoke coming out of the lava dome of Mount Merapi can be seen from Cangkringan, Sleman, DI Yogyakarta. (ANTARA)

YOGYAKARTA - Mount Merapi on the border of Central Java Province and Yogyakarta Special Region (DIY) launched a hot cloud of avalanches 2.5 kilometers (km) on Thursday, towards Kali Boyong.

Head of the Geological Disaster Technology Research and Development Center (BPPTKG), Agus Budi Santoso in Yogyakarta, Thursday, said the hot clouds of avalanches occurred at 05.29 WIB.

"The community is expected to remain calm and be able to carry out activities as usual outside of the designated hazard areas," Agus said as quoted by ANTARA.

Based on seismic records, he said, the avalanche of hot clouds lasted for 225 seconds with an amplitude of 59 mm.

During the period 00.00-06.00 WIB, seven Merapi lava avalanches were observed to be southwest or Kali Sat/Putih and Kali Krasak with a maximum sliding distance of 1,800 meters.

Meanwhile, referring to a visual observation report on the activity of Mount Merapi for the period 19-25 September 2025, the BPPTKG stated that there was a slight change in morphology in the southwest lava dome due to changes in the volume of the dome and lava avalanche activity.

As for the middle dome, no morphological changes were observed.

He said based on air photos on September 25, 2025, the volume of the southwest lava dome of Merapi reached 4,179,900 cubic meters and the central dome was 2,368,800 cubic meters.

BPPTKG still maintains the status of Mount Merapi at Level III or Alert.

The lava fall and hot clouds from Mount Merapi can have an impact on areas in the south-southwest sector which include the Boyong River (a maximum of five kilometers) and the Bedog, Krasak, and Bebeng rivers (a maximum of seven kilometers).

In the southeast sector, including the Woro River is a maximum of three kilometers and the Gendol River is five kilometers. Meanwhile, the ejection of volcanic material in the event of an explosive eruption can reach a radius of three kilometers from the summit.

"We reiterate, as long as you are outside the danger zone mentioned above, you can continue your daily activities safely and calmly," said Agus.