The Philippine Online Chronicles

Farmland in the town of Camanjug in Cebu collapsed Friday, creating a sinkhole that has been expanding ever since.

A sinkhole is a depression in the ground most commonly caused by the gradual dissolution of carbonate rocks collapsing the roofs of underground caves.

Photos of the sinkhole can be seen here, here, and here.

Authorities from the Mines and Geo-Science Bureau (MGB) Region 7 said that the Camanjug sinkhole may have been triggered by the magnitude 6.9 earthquake two weeks ago or its associated aftershocks.

''The earthquake may have caused ground or tension cracks. These factors may have weakened the cave roof,'' MGB7 Senior Science Research Specialist Abraham R. Lucero Jr. told the Manila Bulletin.

The sinkhole was discovered at 6 am on Friday by farm caretaker Walter Pesalbon, who noticed a hole he described as the width of a large cauldron. After an “explosion” two hours later, the hole expanded to ten meters in diameter. By the end of the day, the sinkhole measured 18–20 meters in diameter, becoming shallower as it widened.

Barangay captain Jojo Quirante said that the sinkhole swallowed a mango tree and an electrical post.

“In all my 44 years, this is the first time I’ve experienced something like this here,” he added.

However, environment officials said sinkholes are not unusual in Cebu, where the terrain is made of limestone and karst.

After the February 6 earthquake, sinkholes were found in 11 barangays in the Cebu municipality of Tuburan: Bulwang, Lusong, Montealegre, Santo Niño, Siotes, Kabkaban, Libo, Taminjiao, Kalangahan, Bagasawe, and Sandayong. A further three were found in the barangays Linut-od in Argao, Kang-actol in Dumanjug, and Vive in Ronda, Cebu.

MGB7 warns that people must stay away from the site, as it may collapse at any time.

Officials from MGB7 are expected to visit the Camanjug site today. However, the agency lacks the equipment to properly examine the sinkhole, including a device which uses soundwaves to detect underground caves.