Guatemala Sinkhole Created by Humans, Not Nature

30-story-deep chasm not a true sinkhole, but a "piping feature."

The sinkhole appeared Sunday in downtown Guatemala City, swallowing a three-story building.

Ker Than

for National Geographic News

Published June 3, 2010

Human activity, not nature, was the likely cause of the gaping sinkhole that opened up in the streets of Guatemala City on Sunday, a geologist says.

A burst sewer pipe or storm drain probably hollowed out the underground cavity that allowed the chasm to form, according to Sam Bonis, a geologist atDartmouth College in New Hampshire, who is currently living in Guatemala City (map).

The Guatemala City sinkhole, estimated to be 60 feet (18 meters) wide and 300 feet (100 meters) deep, appears to have been triggered by the deluge from tropical storm Agatha.

But the cavity formed in the first place because the city—and its underground infrastructure—were built in a region where the first few hundred meters of ground are mostly made up of a material called pumice fill, deposited during past volcanic eruptions.

"Lots of times, volcanic pumice originates as a flow [of loose, gravel-like particles], and because of the heat and the weight, it becomes welded into solid rock," Bonis said.

"In Guatemala City [the pumice is] unconsolidated, it's loose," he said. "It hasn't been hardened into a rock yet, so it's easily eroded, especially by swift running water."

In general, the zoning regulations and building codes in Guatemala City are poor, Bonis said, and the few regulations that exist are often ignored. That means leaking pipes could have gone unfixed long enough to create the right conditions for the sinkhole. (Related 

As part of a volunteer team that investigated the 2007 sinkhole, Bonis co-authored a report warning the Guatemalan government that similar holes will very likely keep appearing unless action is taken to inspect the city's sewer system for weaknesses. (Watch video of sewer divers in Mexico City.)

The government never replied, Bonis said—possibly due to a lack of funds.

"There's a minimum of regulation, because that's money that the government doesn't have," he said.

But, he added, "there's got to be ways of inspecting the sewer system. ... These are things that have to be done."