Sinkholes: How do they form, what causes them

7 states are more prone to sinkholes, U.S. Geological Survey says


Sinkholes open from time to time in Central Florida, with some causing major damage to homes and property

What causes the sinkhole to appear?

Florida law defines a sinkhole as a,  "landform created by subsidence of soil, sediment, or rock as underlying strata are dissolved by groundwater. A sinkhole forms by collapsing into subterranean voids created by the dissolution of limestone or dolostone.

According to the U.S. Geological Survey, there are two types of sinkholes: dissolution, cover-subsidence sinkholes and cover-collapse sinkholes.

Dissolution sinkholes occur when limestone or dolomite are exposed to groundwater. Once the breakdown occurs, spaces and caverns can form.

Cover-subsidence sinkholes form when sediments contain sand and cover material is thicker and sediments contain more clay, the U.S. Geological Survey said.

The last type of sinkholes are the most catastrophic and are called the cover-collapse sinkholes. This occurs when sediments have a large amount of clay, officials said.

Over time, surface drainage, erosion and deposition of sediment cause a sinkhole in a shallower bowl-shaped depression.

Florida, Texas, Alabama, Missouri, Kentucky, Tennessee  and Pennsylvania are states where sinkholes are more likely to occur, the U.S. Geological Survey said.

If you have any questions about sinkhole occurrences, The Florida Geological Survey has a database that you can look up the incidences.

Florida law, Section 627.706(2)(a) requires authorized insurers to cover catastrophic ground cover collapse. "The insurer may restrict catastrophic ground cover collapse and sinkhole loss coverage to the principal building, as defined in the applicable policy," the law states.

To read more on the Florida law, visit http://www.leg.state.fl.us/Statutes/index.cfm?App_mode=Display_Statute&Search_String=&URL=0600-0699/0627/Sections/0627.706.html