How could something like this happen? Some say it was related to a leaking storm sewer line. That is still a lot of material to impact. It may have been more gradual occurring over years. Looking at what happens in Central Florida, excessive ground water is pumped from the aquifer. This results in soils and rock bridging air voids in what previously was underwater and subject to lesser loads due to the presence of water. Fractures may occur that convey overlying soils into voids with rainwater runoff, even burst water lines.
http://www.uwex.edu/wgnhs/sinkholes.htm
Reportedly another sinkhole developed here three years ago, see below. That sink hole would add to the loss of material into the underlying void and weakening of the prism of soil. With Tropical Storm Agatha bringing torrential rains even more soils may have been washed into the void as well as adding to the weight of overlying soils. A dome topped cavity may develop in the soils overlying the weathered rock strata, which in time can fracture and collapse catastrophically.
More photos:
From:
http://howtogetridof.com/blog/2009/0...ing-holes.html and
http://www.accuweather.com/blogs/new...-massive-s.asp and
http://conway.rutgers.edu/~ccshan/wi...la_City_abyss/
http://www.dailycognition.com/index....ound-them.html
Previous sinkhole development in 2007. More at:
http://en.wikinews.org/wiki/Broken_s...emala_sinkhole
.