After the recent sinkhole disaster in Guatemala, discussions have begun to take place over where other potentially destructive time bombs might be hidden. A sinkhole is defined as a natural depression or hole in the surface topography caused by the karst processes or chemical dissolution of carbonate rocks. Sinkholes tend to form where there are large deposits of limestone, carbonate rock, and salt beds which are exposed to circulating ground water. As rock slowly dissolves, cave-like spaces develop under the land surface. Now, if these lands that are susceptible to sinkhole formations have been used for development, there exists a large risk for both lose of property and human life.
So what are the risks here in the Philippines? According to the Mines and Geosciences Bureau (MGB) of the Department of Environment and Natural Resources (DENR), many areas have been categorized as having sinkholes or hold the potential for sinkhole formation. By conducting Engineering Geological and Geo-hazard Assessments (EGGA) seven barangays in Bohol, namely Poblacion 3, Bool, Mansasa, Cabawan, Tiptip, Dao and Cogon have sinkhole pockets. In Cebu, an island approximately 60-70% composed of limestone has outlined the following barangay’s as having sinkholes: Barangay Talamban and Cabancalan. To date, there appear no immediate risk for the National Capital Region for sinkhole, or sinkhole formation.
The only way to detect if an area is susceptible to sinkhole formation is through core drilling or ground-penetrating radar. Therefore, any and all concerned local government units are urged to conduct EGGA to identify the possible geological hazards that exist within and in adjacent areas of new development.
Information sourced from:
Manila Bulletin: Indino, P.J. Pocket sinkholes seen in Bohol. June 4, 2010
Manila Bulletin: Sinkholes can occur in Cebu – MGB7 geologist. June 6, 2010