BRIN Says Giant Hole in Aceh Is a Landslide, Not a Sinkhole
A giant ground cavity in Ketol subdistrict, Central Aceh, Aceh province, has continued to expand, reaching an area of 27,000 square metres. The National Research and Innovation Agency (BRIN) has assessed that the hole is the result of a landslide rather than a sinkhole.
Head of BRIN’s Geological Disaster Research Centre, Adrin Tohari, said the Ketol area does not consist of limestone, which typically triggers sinkholes, but rather of tuff material from the now-inactive Mount Geurendong. This tuff, Adrin continued, is a young layer that has not been properly compacted, making it prone to collapse.
“What has occurred in Central Aceh is actually a landslide phenomenon, not a sinkhole. The tuff layer is not compact and has low strength, making it very easily eroded and prone to collapse,” Adrin explained in a statement on Saturday (21/2/2026).
Based on Google Earth satellite imagery dating back to 2010, the Ketol area had already shown a small valley that gradually widened over time due to erosion and landslide processes. Adrin assessed that this process has continued, causing the valley to widen and lengthen until it formed a large cavity.
Suspected Contributing Factors Behind the Expanding Hole
According to Adrin, earthquakes are suspected to have played a role in accelerating the landslide. The 6.2-magnitude earthquake that struck Central Aceh in 2013 is estimated to have weakened slope structures and triggered increasing instability.
In addition to earthquakes, Adrin said heavy rainfall has also been a primary trigger. The fragile tuff rock easily becomes saturated with water, causing soil layers to lose their cohesion and ultimately collapse.
Beyond earthquakes and rainfall, open plantation irrigation channels have also accelerated the landslide process. Water seeping into the ground increases the moisture content of the tuff layers, making them more susceptible to collapse.
“If irrigation channels are open and water continues to seep into the ground, the already fragile layers become increasingly unstable,” he said.
Adrin disclosed a hypothesis that groundwater flow is eroding the boundary between the fragile tuff layer and the denser rock beneath it. This, he said, causes the upper part of the cliff to lose its support and collapse gradually.
He noted that this large cavity phenomenon did not occur suddenly, but is rather a process that has been unfolding over decades to hundreds of years.
Similar Large Cavity Phenomena
Similar conditions can be found in other areas with young volcanic rock geological characteristics. Adrin cited the Sianok Canyon in West Sumatra, which was formed through a lengthy geological process linked to the tectonic activity of the Great Sumatran Fault with similar rock characteristics.
BRIN has not yet conducted direct field research to further confirm the cause of the phenomenon, but has carried out analysis based on satellite imagery and public data.
“We have only been analysing based on imagery data and public information. To determine the cause in detail, comprehensive research is required,” he explained.
Furthermore, Adrin proposed that ground movement vulnerability maps be updated following this event. He also reminded the public to remain vigilant for early warning signs such as the appearance of ground cracks or minor subsidence in the surrounding area.
“Ground movement vulnerability maps already exist, but they need to be updated after this event to be more accurate and operational. What matters most now is understanding the process and immediately taking mitigation steps so that the risk of casualties can be avoided,” he added.