VALDOSTA, Ga. -- Sinkholes seem to emerge out of nowhere, swallowing vehicles and turning streets into gaping craters in seconds.
More than 300 of the dangerous and costly hazards developed around Albany after the 1994 floods, hampering traffic for months and worrying residents who feared the streets would just crumble away beneath them.
James Hyatt, a Valdosta State University assistant professor, rushed to Albany to study the sinkholes. He has been looking for a way to predict and eventually prevent the hazards that are so common in south Georgia.
Mr. Hyatt found sinkholes of all sizes in Albany. One swallowed a large rescue truck, while others devoured homes and left gaping holes in city streets. The sinkholes began appearing after Tropical Storm Alberto dumped two feet of rain on the city in 24 hours.
"It's Swiss cheese over there," Mr. Hyatt said. "There were a lot of cavities ready to go."
John Sperry, Albany's former city engineer, said it is impossible to predict where sinkholes will occur with current technology. And many people were afraid to rebuild in the city because of the threat of future sinkholes.
"The predictability would be marvelous if we could do that, because then you could place buildings and structures in a better place," he said.
Sinkholes are common in areas with limestone or other porous rocks beneath the surface. Groundwater dissolves the rock, leaving caverns. They can enlarge to the point that the earth above gives way. Sinkholes can range from holes a few feet wide and a few feet deep to pan-shaped depressions hundreds of feet wide and 5 or 6 feet deep.
"Sinkholes are an important land form in this part of the country," Mr. Hyatt said. "And they are a significant natural hazard, so they are a land form that influences people. Understanding how they form and where they are is important both academically and from an applied point of view."
One of the biggest on record occurred in South Africa in 1962. Twenty-seven men were killed when the building they were working in dropped into a 100-foot-deep sinkhole that was 180-feet wide at the top.
In addition to wrecking homes, damaging farmland and destroying highways, sinkholes can serve as a conduit for pollutants that seep into the groundwater.
Mr. Hyatt plans to create susceptibility maps to minimize sinkhole damage and hazards. He is currently studying five south Georgia lakes, including 48-foot-deep Lake Balboa, that were formed thousands of years ago by sinkholes.
Mr. Hyatt and a Canadian colleague, Robert Gilbert from Queen's University in Kingston, Ontario, used sensitive sound equipment to map the lake bottoms and analyze the sediment in one of the lakes. The sediment provides a historical record of changes to the landscape and vegetation of the area, he said.
Barry F. Beck, who has been studying sinkholes for 30 years, says engineers currently use complicated studies to find out if an area they are considering building on is prone to sinkholes.
"The main problem is that these investigations are extremely expensive," said Mr. Beck, former head of the Florida Sinkhole Research Institute. "They're rarely feasible for a single-family home. They are much more important under roadways, airports, hospitals and major structures where public safety is involved."