Families evacuated sinkhole forms in Santa Fe islet

CEBU, Philippines - The Department of Environment and Natural Resources-7 through its Mines and Geosciences Bureau-7 will be sending a geologist to Kinatarcan islet in Santa Fe town in northern Cebu following a sinkhole that formed in the area.

The sinkhole, which the Office of the Civil Defense Central Visayas confirmed, reportedly measures 40 feet in diameter and has a depth of about 40 feet. It was discovered by some residents of the area yesterday.

The Cebu Provincial Disaster Risk Reduction Office said 30 families have been evacuated and the area where the sinkhole formed has been secured.

MGB-7 Director Loreto Alburo has recommended fencing the area and for a signage to be put up to warn people of the possible danger in going near there.

"I strongly advised the local government unit officials to strictly not allow people to come nearest to the sinkhole as we are still determining the extent of its formation," Alburo said.

Alburo said MGB-7's geosciences division chief Al Emil Berador will check the area.

Sinkholes are common where the rock below the land surface is limestone, carbonate rock, rocks that can naturally be dissolved by circulating ground water.

As the rock dissolves, spaces and caverns develop underground.

Sinkholes can be dramatic because the surface land usually stays intact until there is not enough support. Then, a sudden collapse of the land surface can occur.

This was manifested by the sinkholes that formed following the magnitude 7.2 earthquake that struck Central Visayas last year. As of July 25, about 205 sinkholes have been recorded in Bohol alone.

According to the Visual Dictionary of the Earth, caves commonly form in areas of limestone. Limestone is made of calcite (calcium carbonate), which dissolves in the carbonic acid naturally present in rainwater, and in humic acids from the delay of vegetation.

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. —/JMO) (FREEMAN)