DON'T CALL THE GUATEMALA SINKHOLE A SINKHOLE
Analysis by Michael Reilly
Wed Jun 2, 2010 09:34 PM ET
The giant sinkhole that opened beneath downtown Guatemala City over the weekend is all the rage right now. There's just one problem: it isn't a sinkhole.
"Sure, it looks a lot like a sinkhole," geologist Sam Bonis told Discovery News from his home in Guatemala. "And a whale looks a lot like a fish, but calling it one would be very misleading."
Instead, Bonis prefers the term "piping feature" -- a decidedly less sexy label for the 100-foot deep, 66-foot wide circular chasm. But it's an important distinction, he maintains, because "sinkholes" refer to areas where bedrock is solid but has been eaten away by groundwater, forming a geological Swiss cheese whose contours are nearly impossible to predict.
The situation beneath the country's capital is far different, and more dangerous.
The lion's share of the city is built on pumice fill -- ash flows made up of loose, gravel-like particles deposited during ancient volcanic eruptions. In places, the debris is piled over 600 feet thick, filling up what would otherwise be a v-shaped valley of faulted bedrock.....(SNIP)
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by mislabeling the feature a sinkhole, it distracts from a dangerous situation that could be mitigated, if not neutralized, by better handling of the city's runoff and waste water.
(MORE)
http://news.discovery.com/earth/dont-call-the-guatemala-sinkhole-a-sinkhole.html-----------------------
And here's a whole bunch of info--wiki, on Guatemala City--including the latest on the "sinkholes" ("piping features"). See "Piping Pseudokarst" (about 3/4 down the page). The latest from the experts is that all the "sinkholes" (I've counted three, so far, googling) are related to an aging, leaking sewage system which is eroding these light soils that filled in volcanic pockets long ago.
Ergo, it's a MODERN problem.
Lord, Guatemala City has been occupied since 1000 BC! It was a major Mayan city (Kaminaljuyu) and later the capitol of "the United Provinces of Central America" (1821) after independence from Spain. It was a small Spanish town for a while, before that, and then, when colonial Spain's capital in Central America (Antigua Guatemala) was hit by earthquakes, Spain moved their capitol to Guatemala City. Now it is THE major hub of Guatemala and major seaport.
I think all three "sinkholes" have been in poor neighborhoods--so that may be the heart of the matter--neglect of the aging sewer system because the rich in the glitzier parts of the city don't care. Could be. Not sure.
It looks like quite a beautiful and interesting city.
http://en.wikipedia.org/wiki/Guatemala_City