By CESAR JOLITO III
The ground movement at Barangay General Luna in Negros Occidental’s Toboso town should not yet be interpreted as a sinkhole or landslide following the Mines and Geosciences Bureau’s (MGB) initial site visit, which was focused on surface assessment, mapping and terrain analysis only.
“There are no official findings yet. What was done was purely surface assessment,” Hospicio Carbajosa Jr., officer of the Toboso Municipal Disaster Risk Reduction and Management Office, said yesterday.
Carbajosa explained that the area in Sitio Bairan is geologically classified as limestone, which is why MGB is giving particular attention to the possibility of underground cavities.
However, during the initial inspection conducted with teams from the Provincial Environment Management Office and the Provincial Disaster Risk Reduction and Management Office, no bedrock was exposed.
Investigators only observed movement in the topsoil layer.
“The bedrock, which is usually closer to the water table, was not seen. What moved was only the surface or topsoil,” Carbajosa added.
Drone footage was gathered to measure the length, width and depth of visible cracks, particularly along Level Street in Sitio Pairan, where the affected zone spans an estimated 60-meter diameter.
Despite the presence of deeper cracks in some portions, MGB has not declared the area a sinkhole or landslide pending further scientific testing.
The technical team is scheduled to return in the second week of March with specialized equipment to conduct subsurface investigations, which will help determine whether cavities or other geological features exist beneath the ground.
In the meantime, the area remains cordoned off as a precaution.
Residents and passersby have been advised to stay alert, especially after rainfall, which authorities noted could be a triggering factor for further soil movement.
During the latest monitoring, ground displacement increased by about one inch compared to earlier observations.
Earlier, local disaster officials were concerned over a rapidly worsening sinkhole discovered on a mountainside in Toboso, as its depth and size continue to increase following days of rainfall.
Carbajosa said the ground opening had deepened from six feet to nine feet in just 24 hours, underscoring the risk of further ground collapse.
The sinkhole, which now spans a radius of about 30 meters and a diameter of roughly 60 meters, lies around 500 meters from the East Negros Fault System.
Carbajosa explained that the area’s limestone-rich terrain makes it highly susceptible to sinkholes, especially during prolonged or heavy rains.
“When there is continuous rainfall, the limestone dissolves, weakening the ground structure and causing it to sink,” Carbajosa said, noting that the site is also near the Calatrava-Toboso earthquake fault line, part of the same fault system./CJ, WDJ