State phenomena and sinkholes in U.S.

By Our Special Correspondent

THIRUVANANTHAPURAM, AUG. 9. The phenomena of sinkholes, which are frequent in some areas of the United States such as Florida, have many things in common with some of the phenomena occurring in the State.

In many parts of Kerala, the ground had sunk considerably, abruptly creating depressions like wells on the ground. There were also separate incidents of walls of buildings developing cracks and wells collapsing.

By definition, a sinkhole is a small steep depression caused by the dissolution and collapse of subterranean caverns in carbonate formations. They can develop unexpectedly as the land surface collapses into underground gravities (void spaces that range in size from small openings to large caverns).

There are several types of sinkholes. One is the relatively fast forming cavern collapse sinkhole which can produce deep depressions suddenly. Another is the cover subsidence type which is slow moving and causes cracks on the interior and exterior of buildings. This is often difficult to distinguish from other land subsidence like soil slump. However, technology is available to distinguish them and determine areas which are prone to development of sinkholes.

Though the depressions that occurred in Kerala are different in shape and smaller than many in Florida, there are features such as the suddenness of occurrence and nature of collapse that are common to both. The cracks developed on walls in Kerala are similar to those occurring in Florida.

However, there is little chance of this season's rain alone having caused this phenomena in Kerala. Dissolution of underground formations would take time. Collapse of openings beneath the ground is just a possibility. Detailed studies would be required to determine exact mechanism of the sinkholes in Kerala.

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Section  : Southern States
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