The Tennessee Department of Transportation says the asphalt at the intersection of College Street and North Second Street is sinking because of aging sewer and drainage lines deep beneath the ground.
What are Sinkholes?
A sinkhole in Saint-Jude, Quebec has just collapsed a house, killing a family of four inside, leading people to ask what they are, how they occur and obviously who is at risk.
Sinkholes are depressions that occur when soil or bedrock has been removed and only air remains - commonly when the rock below the land surface is limestone, carbonate rock or salt beds that have been naturally dissolved by ground water circulating through them and then the water dries up.
As the rock is dissolved by water(dissolution), spaces are created (suffosion) and typically sinkholes happen suddenly because the surface stays intact until the weight becomes too much.
Sinkholes occur more often in places like Florida and Alabama because they have more underground rivers than most other states. When sinkholes form it is commonly because the ground has simply collapsed over underground rivers that were once filled with water.
So if you want to look for signs of a major drought in the making, disgruntled skiers at Lake Tahoe are not going to be as accurate as sinkholes.
Read more at http://www.science20.com/news_articles/what_sinkhole_and_why_do_sinkholes_form
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