The appearance of a massive sinkhole in Guatemala City (map), Guatemala, on Sunday is thought to have been triggered by tropical storm Agatha, a violent tempest that struck Central America over the weekend.
From photographs, the new Guatemala sinkhole appears to be about 60 feet (18 meters) wide and about 300 feet (100 meters) deep, said James Currens, a hydrogeologist at the University of Kentucky—which explains how the sinkhole was reportedly able to swallow an entire three-story building.
Sinkholes can form when water-saturated soil and other particles become too heavy and cause the roofs of existing voids in the soil to collapse, Currens said.
Another way sinkholes can form is if water enlarges a natural fracture in a limestone bedrock layer. As the crack gets bigger, the topsoil gently slumps and develops into a sinkhole.
In either case, the final collapse can be sudden, Currens said.
Photograph courtesy Paulo Raquec
Sinkhole Spurred by Storm?
The roughly 30-story-deep sinkhole in Guatemala is seen from street level on May 31, 2010.
Sinkholes are particularly prevalent when heavy rains follow a long period of drought, said Jonathan Martin, a geologist at the University of Florida.
Drought can empty subterranean cavities of water, making them less able to support the overlying soil—flooding only adds to the danger. "If there's a tropical storm and all of a sudden the soil above the cavity is filled with water instead of air, the weight will cause the [sinkhole] to collapse," Martin said.
Photograph by Johan Ordonez, AFP/Getty Images
Cop Skirts Sinkhole in Guatemala
A police officer walks by the sinkhole in Guatemala City on May 30, 2010—the day the sinkhole appeared.
It probably isn't safe to venture too close to the chasm, Currens, the hydrogeologist, said. The sinkhole could still grow.
Depending on the makeup of the subsurface layer, the sinkhole in Guatemala "could eventually enlarge and take in more buildings," he said.
The 2010 sinkhole could have formed in a similar fashion, Currens said. A burst sanitary or storm sewer may have been slowly saturating the surrounding soil for a long time before tropical storm Agatha added to the inundation.
Sinkholes typically appear in places where the subsurface bedrock is made of limestone, said the University of Florida's Martin, because limestone is more easily eroded by water.
The 2010 sinkhole in Guatemala (pictured) had likely been forming for several weeks or even years before floodwaters from tropical storm Agatha caused the sinkhole to cave in, the University of Kentcky's Currens said.
"The tropical storm came along and would have dumped even more water in there, and that could have been the final trigger that precipitated the collapse," Currens said.