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Pressed to comment whether he supports the planned evacuation of some 200 families living in five puroks in Poblacion Uno who may be in danger of being swallowed by sinkholes, also called by other experts as underground caves, Tirol answered: “Only for the houses over the crack.”

Asked further if he has any advisory to those who are worried of their safety, their homes, and property, Tirol replied: “Ang advise maggikan ra sa mga alagad sa gobyerno. Ang ako opinion o panahom lang.”

In 1998, Engineer Jes Tirol became a voice in the wilderness incessantly urging church and government officials to undertake a retrofitting project on Bohol's centuries-old churches so that these structures of national heritage could withstand earthquakes.

But his calls fell on deaf ears. Tirol, writing in his weekly column in the Bohol Chronicle, lamented that church officials instead of undertaking massive retrofitting of church buildings they became engrossed with “beautification.”

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Other residents have also questioned the ground-penetrating-scanning (GPS) conducted by MGB on Poblacion Uno.

Doris D. Tan, a Boholana who is convinced of the looming danger in said place, wrote: “If there is a gaping sinkhole in the midst or very near my home and a report has been released by the authorities that this opening is an entrance of not just a single cave but a honeycombed caves, would I still wait for my government to tell me what to do?”

“It is the same way that during an earthquake and even at its aftermath, people refuse to go back to their houses and opt to live in tents for fear that the next aftershock will bring their houses down on them. And nobody ordered them to do that. It is the instinct of self preservation. So, if there is a great probability that the ground under my feet will at anytime give in, what do you think will I do?”

Sinkholes, according to Britannica Encyclopedia, is defined as a “topographic depression formed as underlying limestone bedrock is dissolved by groundwater. It is considered the most fundamental structure of karst topography.”

“Sinkholes vary greatly in area and depth and may be very large. There are two main varieties, one caused by the collapse of the roof of a cavern, the other by the gradual dissolving of rock under a soil mantle. Collapsed sinkholes generally have steep rock sides and may receive streams that then flow underground. The soil-mantled sinkhole is generally shallower than the collapsed sinkhole and receives local drainage; it may become clogged with clay and hold a small lake. Some sinkholes, formed at low sea-level stages during the Pleistocene epoch, are now half-drowned and are known as cenotes,” the resource book said. (MIKE ORTEGA LIGALIG)

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Why does limestone change into marble?

High heat and pressure cause the calcite in the limestone to recrystallize into larger crystal structures.

But...

Coastal limestones are often eroded by organisms which bore into the rock by various means. This process is known as bioerosion. It is most common in the tropics, and it is known throughout the fossil record (see Taylor and Wilson, 2003). -http://www.ask.com/

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He he, basin borit characterized by high heat and pressure, pwede na...



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