Image source: U.S. Geological Survey
(http://wrgis.wr.usgs.gov/docs/parks/cave/)
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Florida's famous sinkholes are important evidence that sea level was higher in the past. Sinkholes only form in areas where limestone bedrock occurs. Fossils show that Florida's limestone bedrock formed in ancient marine water environments. However, when sea level falls, the limestone becomes exposed on the land's surface. It becomes exposed to freshwater from rain, limestone will start to dissolve, forming caverns. Image source: U.S. Geological Survey (http://wrgis.wr.usgs.gov/docs/parks/cave/) |
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As caverns in the limestone expand over time, their ceilings may collapse, forming sinkholes. These sinkholes can form suddenly, destroying homes, cars, and other property when they collapse. Sinkholes are found throughout central and southern Florida. Where groundwater levels are shallow, many of these sinkholes are now filled with water, forming the many lakes and ponds that occur throughout the region. Sinkholes do not form in areas where Florida's bedrock consists of non-calcareous sedimentary rocks (shale and sandstone). These sediments accumulated in the past in regions where terriginous sediments were washed in from other areas along the Gulf Coast. |