When the earth trembled in Cebu and Davao Oriental earlier this month, the damage wasn’t only seen in cracked walls or fallen debris. Days after the shaking stopped, another danger quietly emerged. The ground itself began to collapse, giving rise to sinkholes.
After the magnitude 6.9 earthquake that struct northern Cebu on September 30, residents began reporting strange depressions, widening cracks, and holes that seemed to appear overnight. Geologists from the Mines and Geosciences Bureau (MGB-7) confirmed that at least 70 sinkholes had since formed across several towns in the area.
The cause? Much of Cebu Island rests on soluble limestone bedrock, which gradually dissolves when exposed to water leaving hidden subterranean voids. When an earthquake shakes such terrain, these voids can collapse without warning.
One of the most startling discoveries came from Barangay Cogon in Bogo City, where a sinkhole opened beneath a site serving as evacuation area for residents. Thankfully, no one was hurt, but it was a chilling reminder that even supposed safe zones may not be as stable as they appear.
MGB has since issued advisories declaring parts of northern Cebu as subsidence-prone areas, cautioning local governments to avoid construction or resettlement until detailed hazard assessments are completed. Experts warn residents not to cover sinkholes with soil or debris because it may only hide the risk, not remove it.
Meanwhile, on October 10, the region of Davao Oriental was struck by a double quake with magnitudes 7.4 and 6.8 quakes that triggered landslides and shook a broad region in Mindanao. While reports of sinkholes remain limited, the region’s coastal and limestone-rich terrain make it vulnerable to similar collapses. Geologists are now conducting assessments to detect any hidden ground weaknesses.
These incidents serve as a sobering reminder that earthquakes do not only topple what’s above the surface — they can also hollow out what lies beneath. The real danger is often invisible, until the ground literally gives way. Cracks in the yard, tilting fences, or sudden changes in water flow can all signal instability. Communities are urged to coordinate with their local disaster offices and refrain from returning to unsafe areas until assessments are complete.
Sinkholes may also stem from human activities. The water below ground is helping to keep the surface soil in place. Groundwater extraction for water supply and for irrigation can produce new sinkholes. If pumping results in a lowering of ground-water levels and the upper layers of the ground cannot support the weight anymore, then the ground gives way suddenly to reveal a sinkhole.
Broken underground pipes and sewer lines may cause the ground to collapse. A 50-meter-deep sinkhole in the middle of the road in Bangkok, Thailand, that appeared on September 24, 2025 was likely caused by a ruptured water pipe linked to the adjacent underground subway construction.
In short, subsidence threats are real — whether triggered by nature’s tremors or by man-made changes. Recognizing the warning signs, staying away from unstable ground, and heeding official hazard-maps can help communities stay safe.