Guatemala City Sinkhole: How Did It Happen?

June 1, 2010— -- It almost looks too massive and menacing to be real.

After Tropical Storm Agatha hit Central America over the weekend, a gaping sinkhole in Guatemala City swallowed a three-story building. According to some reports, the hole is about 200 feet deep.

Though scientists say sinkholes are common in certain parts of the world, some said that this one took even them by surprise.

"A lot of us who study sinkholes look at this and go, 'wow,' it does seem a little bit bizarre," said Randall C. Orndorff, a program coordinator with the U.S. Geological Survey.

Orndorff said that sinkholes are common in places with rocks, such as limestone and gypsum, that can be naturally dissolved by water.

In those so-called "karst" areas, caves and voids form underground as the rocks dissolve, he said. After heavy rains or extreme drought, sinkholes can suddenly form naturally as the underground spaces open up and can no longer support the land at the surface. Human activity, such as construction, can also lead to the same consequence.

In the U.S., he said, Florida, parts of Texas and the area around the Great Lakes are most vulnerable to sinkholes.

But geologists familiar with Guatemala say the issue there isn't limestone.

"The area in the city is underlayed by volcanic deposits, and these volcanic deposits make very steep-bounded canyons," said William Rose, professor in the geological engineering & sciences department at the Michigan Technological University.

In February 2007, a 330-foot sinkhole opened up in Guatemala City, also after heavy rains.

"It was found that it was due to sewer arrangements of the city, which had undermined the area. I suspect it's the same thing," he said.

Orndorff also said that though more investigation is needed, it seems that old infrastructure is to blame for the recent sinkhole.

"If you think of a sewer or water line, it's a manmade cave. At some point, if they fail, all of the soil above it and to the surface goes with it," he said.

Human Activity Can Cause Sinkholes

Orndorff said that while karst areas are most prone to natural sinkholes, infrastructure problems could lead to sinkholes anywhere.

"The reason I think we're seeing more and more … is because our population has grown so much," he said. "We're building in karst areas, which are great for farming and agriculture. Now as cities develop, we're expanding into those areas."

In May 2008, he said a sinkhole in Daisetta, Texas, opened up after an underground salt dome collapsed. It ended up stretching three football field lengths in diameter and plunging 150 feet into the ground.

But he said that the most catastrophic sinkholes occur in places with mature karst development, such as Papua New Guinea, Borneo and Indonesia.

Sinkholes in those areas have been known to be a mile or two across and hundreds of feet deep.

Sometimes he said fractures in the ground or slight depressions can indicate that a sinkhole might be about to occur, but often the ground can collapse suddenly without warning.