DAVAO CITY, Philippines – A total of 135 sinkholes were identified by the Mines and Geosciences Bureau in different areas of Island Garden City of Samal in Davao del Norte.
Lowell C. Chicole, action officer of MGB-XI said the discovery of the sinkholes was based on the hazard mapping assessment conducted in Samal last May 2015.
He pointed out that a collapse of a sinkhole is one of the most dangerous geo-hazards that may happen due to its extreme unpredictability.
Chicole said most of the area in Samal including the Talikud island are prone to a so-called Karst subsidence hazard, where dissolution of limestone by fluid flow in the subsurface causes the creation of sinkholes.
MGB said the topography of Samal Island in general is composed of wide terraces which is mostly characterized by flat terrain, and rarely interrupted by topographical variations.
It added that the changes are mostly attributed to depression and sinkholes that have been produced by collapse or dissolution of the underlying limestone.
Chicole said that caves and other solution cavities are also called kast formations which are also another indicator of limestone area.
“Using a deep penetrating radar in the area and a computer, we identified the areas where sinkholes are present,” he said. (davaotoday.com)