More than 90 households or about 237 persons were evacuated in a church in Sitio Dapdap, Barangay Langub, Kinatarkan Islet in Santa Fe, Bantayan Island in Cebu as a result of the newly-developed sinkhole with a diameter of 10 meters by 14 meters with a depth of one meter.
“The affected area including the subsidence or the sinkhole with some tension cracks is about 20 meters by 40 meters which continues to be progressing is underlain or carpeted with coralline limestone belonging to the Carcar formation,” said Mines and Geosciences Bureau (MGB ) 7 chief geologist Al Emil Berador who conducted an ocular inspection yesterday.
Berador noted the sinkhole continues to move and going closer to the affected area is not safe among the residents adding the recommendations to put up a signage or cordon off the area and conduct a continuous monitoring should be sustained.
MGB 7 Regional Director Loreto B. Alburo earlier recommended to the local government units to take important precautionary measures four days ago after he received a phone call from Santa Fe Mayor Jose Esgana last July 26.
He said the collapse or cave-in of the cave roof which resulted to the formation of a sinkhole may have been trigged by the intense and prolonged precipitation brought about Typhoon Glenda and a low pressure area over the weekend.
Berador added sinkhole development is one of the geological ‘natural’ processes that could occur in the islet.
The residents noticed last July 26 that a portion of a slight sloping ground in Sition Dapdap started to fall down with some tension cracks. Around 92 households with 102 families or 237 persons are now placed in the Seventh Day Adventist Church as temporary evacuation site.
A number of houses were seen about 10 to 15 meters away from the subsidence or sinkhole area.
“We will be identifying a possible relocation site within the islet where these affected communities will be able to live safer and continue to live normally without fear on the geologizal hazards like sinkholes,” said Alburo.
Alburo said the identification of a relocation site is part of the technical assistance that will be provided to the local government unit making sure the communities are away from danger.
The formation of sinkholes occurred more than five million years ago and has been continuously developing through time because of the nature of the underlying rocks, actions of rainwater, and the rise and fall of the water table.
A sinkhole, also known as a sink, shake hole, swallow hole, swallet, doline or cenote is a natural depression or hole in the surface topography caused by karst processes – the chemical dissolution of carbonate rocks.
The acidic water trickles down through cracks and joints in the limestone and between rock layers, breaking up the surface terrain into clints (blocks of rock), separated by grikes (deep cracks), and punctuated by sinkholes into which surface streams may disappear.
Meanwhile, Berador conducted a lecture on the geological hazards present and some measures with Cebu Provincial Disaster Risk Reduction and Management Officer Baltazar Tribunalo who conducted a briefing on community-based disaster risk reduction to close to 200 residents including the affected ones in the said islet.
Also, Barangay Captains Rolando Villacarlos, Vilma Dawa and Romy Illut of Barangays Langub, Hagdan and Kinatarkan, respectively, attended the said activity.
In a related development, Berador inspected four schools or three elementary and one high school for possible damage brought about by the sinkholes.