There’s no immediate danger for residents living near a sinkhole in sitio Baclayan, barangay Cambuang in Dumanjug town, geologists yesterday.
But they are alarmed at the sight of a growing number of curious onlookers flocking to the ever-expanding sinkhole.
They also voiced surprise over reports of “boiling water” in a coastal barangay in Dumanjug.
They are likewise considering the possibility that a cave and subterranean river system or water channel could be found under the sinkhole (see related story on Page 31).
“More people are flocking there. It’s very dangerous because their weight may cause the sinkhole to widen further. They should refrain from staying in the area and watching the sinkhole,” geologist Jun Lucero said.
Lucero is part of a geologist team sent by the Mines and Geosciences Bureau of Central Visayas (MGB-7) to inspect the sinkhole that broke out more than a week ago.
Lucero said while there’s still no need to evacuate a house 20 meters away from the site, he said the crowd presence could aggravate the area surrounding the sinkhole.
When Cebu Daily News visited the sinkhole, about 30 people gathered outside the fence of the sinkhole and along the roads.
Dumanjug Mayor Nelson Garcia joked that if people continue to come, the locals should sell food in a safe zone within the area so they can earn a living there.
But Lucero was anything but humorous as he recommended to local officials to set up a barbed-wire fence to keep people out of the sinkhole area.
A no-entry sign in the area should also be set up, he said.
Police and barangay tanods are posted in the area to monitor the ground movement and check for trespassers.
They also adjust the yellow police line as the gap continues to widen.
As of yesterday noon, Lucero measured the sinkhole at 10 meters long and 8.5 meter wide with a depth of three to four meters.
‘Big as a cathedral’
He said the big cracks on the sinkhole’s border indicate that it would continue to widen.
The sinkhole that used to be the size of a cooking pan has grown large and wide enough to “swallow” a four-wheel vehicle.
Rains would only cause the soil around the sinkhole to cave in, Lucero added.
He said the presence of sinkholes is natural in Cebu since 70 percent of the total land area of the province is made up of limestones.
“We have many sinkholes in Cebu,” Lucero said.
He said one cannot predict when sinkholes will occur. Lucero said people would know only after the soil collapsed.
Lucero said they even saw a sinkhole under a cave that was as big as a cathedral in Pinamungahan town.
The MGB-7 geologist explained that limestone easily dissolves in water, which creates the cavities or gaps in the subsurface.
Lucero said they need a ground-penetrating radar to determine the geometry of the sinkhole’s cavity, its maximum length and width.
He said the MGB-7 may consider renting equipment from a Manila-based firm.
He said all they can do for now is monitor the area and measure the sinkhole.
With no equipment, Lucero said they can’t determine the extent of the sinkhole and the possible cavities that still interconnect underground.
Lucero also said they dropped by barangay Looc, a coastal area in Dumanjug town, after locals reported seeing “boiling” water in the ocean.
He said the locals saw it three days after the Feb. 6 earthquake that hit the Visayas.
He said the locals told them that the boiling water could be seen during low tide.
But Lucero said the team was unable to spot the “boiling water” since there was high tide in the area during their visit.
Lucero refuted reports that there was volcanic activity there because the nearest volcano is in Canlaon town, Negros Oriental.
He said they will return to the area to take water samples and conduct seawater and ground assessment.
Lucero said the sighting could not be linked to the sinkhole since they are relatively far from each other.
He said it could have been triggered by the 6.9-magnitude earthquake that affected hydraulic activities underwater.
For his part, Mayor Garcia suggested that Cebu City and Cebu province should invest in a facility because of the high landslide incidence in Cebu.
“It’s a good idea for the province to buy that. It would also be income generating,” he said.