The science of sinkholes - and what you need to know
There are some stories that are so scary that they grab media focus and public attention - the result is that the fear generated can outweigh the actual risk. Every summer, there's a spate of horrifying shark attack stories, yet the risk of being attacked by a shark is pretty remote compared to more mundane every day risks.
This year's candidate for scare story of the year might just be sinkholes. The idea of the ground collapsing below our feet and swallowing us up is pretty horrific, and made more real by the news that a Florida man sleeping peacefully in his home was sucked into a sinkhole so cavernous his body was never found. It seems that there has been a "sinkhole of the week" story in the news ever since then. This month's Atlantic Magazine features a jaw-dropping photo gallery of global sinkholes.
Are sinkholes happening more frequently or are we just noticing them more?
For the science of sinkholes, you can't do better than U.S. Geological Survey. USGS reports that only about about 20% of the country has geological underpinnings that are favorable to the formation of natural sinkholes. Florida might be the nation's top hotspot, but other U.S. hotspots for sinkholes include Texas, Alabama, Missouri, Kentucky, Tennessee and Pennsylvania. However, they can and do happen anywhere. Urban development and infrastructure such as pipelines, sewers, and other developed structures can collapse causing a sinkhole. We've experienced a few recently here in New England - see the garbage truck that was swallowed in SommervilleÂ Â or the neighborhood in Manchester NH that had an outbreak of collapses. Plus, heavy rains can cause roads to collapse - which is why it is dangerous to drive through standing water as one of the drivers in the Atlantic's photo gallery demonstrates.
The Insurance Information Institute offers some good information on insurance and sinkholes. They note that most insurance policies exclude coverage for earth movement, but some states require insurers to offer optional sinkhole coverage for an additional premium - either as an endorsement to a property insurance policy or as a stand-alone policy.
"Offering insurance coverage for sinkholes is a challenge for insurers. When home insurance policies are priced, the real estate value of the land is excluded. Property is insured for what it would cost to rebuild the structure; the price of the land is not factored into the premium that is collected. For this reason, most property insurance policies in the U.S. exclude damage related to movement of the earth. The problem faced by insurers is that sinkholes are hard to predict, difficult to investigate and extremely costly to repair."