THE Mines and Geosciences Bureau of the Department of Environment and Natural Resources said at least 815 sinkholes were found in three barangays in Boracay Island based on the Karst Subsidence Hazard Mapping conducted from 2021 to 2022.
Boracay Island, one of the world’s top island destinations, is made entirely of limestone, where sinkholes are formed, MGB Geosciences Division Chief Engr. Mae Magarzo explained.
The chemical composition of limestone is calcium carbonate which melts when it comes in contact with acid, especially acid rain, she furthered.
“Sinkholes are land depressions due to the removal of support underneath due to earthquake, or due to the lowering of the ground waters,” Magarzo said.
“These sinkholes are not found in other types of rocks but exclusively in limestones areas,” Magarzo added.
The number of sinkholes in Boracay has been increasing in recent year. In 2018, the Karst Subsidence Hazard Mapping identified 789 sinkholes. These rose to 801 in 2019 and 814 in 2020.
Magarzo said a sinkhole is the most dangerous type of hazard because it has indication of when it will appear and collapse from sinkholes happen very suddenly and without warning.
To minimize risks, MGB recommended that the carrying capacity of the island “must be observed” as it is vulnerable to sinkholes.
Magarzo suggested lessening the weight of the structures that stand on the limestone by having only one-story buildings.
metrosundaily
