Massive Sinkhole Swallows Chicago Street
Residents Wonder When They Became Florida
A massive sink hole swallowed half a street and adjoining parkway on Chicago's South Side late Sunday night. The culprit was allegedly a water main break.
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Sink holes form when land gives way leaving a crater-like depression, or hole in the ground. They form most commonly, when groundwater (or in this case, water from a water main) flows through the rock leaving behind underground holes and caverns. When the ceiling of one of these caverns collapses it takes the land and whatever else is on that land - roadway, house, or, as in the case of another Chicago sink hole earlier this year, three cars - with it.
Despite Chicago's recent spate of sinkhole activity, the city does not bear the mantle of the most sinkhole prone region of the country.
According to the U.S. Geological Survey sink holes are most prevalent in "karst terrain" or areas where the type of rock below the ground is easily dissolved by ground water circulating through them. Tough terrain like the metamorphic rock which anchors all of New York City's Skyscrapers, are not particularly prone to sink holes because their salt content is relatively low - they're tough to dissolve.
By contrast, the salt, gypsum, anhydrite, limestone, and solomite are highly soluble, as you can see from this map.
Roughly 20% of the country is over karst terrain and susceptible to "sinkhole events." The most damage from sinkholes tends to occur in Florida, Texas, Alabama, Missouri, Kentucky, Tennessee, and Pennsylvania. Florida in particular is notable not only for its beaches and theme parks but for its often spectacular sink holes like this one which swallowed a large portion of a resort this past August. The most infamous sink hole in recent years, however, has been the sinkhole slowly swallowing the Louisiana town of Bayou Corne. The sinkhole is allegedly the result of petrochemical mining.
As for the Chicago sinkhole, repairs are apparently underway.
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