Did you know that around 40% of the U.S. lie in areas prone to sinkholes?
You don’t believe me? Watch these geological US sinkhole maps.
This map from the U.S. Geological Survey shows the various water-soluble rock underlying different areas of the United States that are prone to sinkhole formation (Description of map and colors in SHNS map courtesy U.S. Geological Survey). Sinkhole damages are the highest in Florida, Texas, Alabama, Missouri, Kentucky, Tennessee, and Pennsylvania.
MAP COURTESY U.S. GEOLOGICAL SURVEY (ONLY KARST => 20%)
As you just figured it out, it’s not only Florida that needs to worry about sudden cave-ins and sinkholes but between 20% (only karst) to 40% (salt, gypsum and karst) of the USA.
Indeed, sinkholes are common where the rock below the land surface can naturally be dissolved by groundwater circulating through them, i.e. limestone, carbonate rock, salt beds, karst. These types of rocks are represented in the map below.
MAP COURTESY U.S. GEOLOGICAL SURVEY (SALT, GYPSUM AND KARST=> 40%)
This second map shows areas of the United States where certain rock types that are susceptible to dissolve in water. In these areas the formation of underground cavities can form catastrophic sinkholes. These rock types are evaporites (salt, gypsum, and anhydrite) and carbonates (limestone and dolomite). Evaporite rocks underlie about 35 to 40 percent of the United States, though in many areas they are buried at great depths. In addition to these natural sinkholes, man-made soil disturbances can result in a sinkhole almost anywhere in the USA.
All you need to know about sinkholes is contained in this very interesting article.
And how do I protect or insure myself or any of my belongings against sinkhole? In Florida and Tennessee insurers are required to offer sinkhole coverage with home policies. In other states, you have to ask for it to get it. And keep in mind, if you do not have this insurance you are not covered. So if you want such a sinkhole coverage policy ask your insurer.