Photo Gallery: Sinkholes in Eastern Hillsborough & Polk counties
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Here's some information on sinkholes from 10 Connects Meteorologist Bobby Deskins:
According to researchers at the University of Florida, "Sinkholes originate beneath the surface when groundwater moves through the limestone and erodes large voids, or cavities, in the bedrock. When water fills a cavity, it supports the walls and ceiling, but if the water table drops, the limestone cavity is exposed to further erosional processes that eventually result in the collapse of the cavity, causing a sinkhole."
Sinkholes can be found around the world, but because of Florida's unique subsurface structure of limestone, mineral deposits and flowing water underground, Florida has the highest amount of sink holes in the U.S.
The limestone layer beneath the surface here in Florda is porous, allowing water to move through it. Occasionally, that flow of water runs into confining layers of mineral deposits such as sand, silt or clay that can clog the pores of the limestone. This causes a winding pattern of underground water flow. This flow of water gradually erodes parts of the limestone creating cavities or caves underground. Those cavities typically fill up with water which helps to support the weight of the walls and the ceiling of the cavities, or the ground we walk on.
In times of drought however, the water table can be seriously depleted. We are now in the third year of a serious drought with rainfall deficits roughly 30 inches below normal for that time period. As a result, many of those water filled cavities under the ground have emptied and have left behind hollow cavities. Without the pressure of the water to help support the walls of the cavities, the ceiling collapses creating sinkholes.
The location of sinkholes can vary according to many factors. Some areas simply have more cavities than others, while human activates such as construction, development and creation of manmade lakes or drainage ponds can add weight to the surface thus adding extra pressure on the walls of the underground cavities.
Also, as freezing temperatures threaten area crops during the winter, farmers will pump water from the subsurface aquifers to spray on the crops to help prevent damage from the cold. During those times, we can see sinkholes pop up in and around the farm areas as the water table drops providing less pressure to support the cavity walls. As the drought continues, additional erosional forces help to breakdown the limestone support and more sinkholes open up as a result.
Believe it or not, heavy rains after a drought can also create sinkholes. When heavy rains fall and percolate into the ground, the enhanced flow of water can further erode already weakened cavity walls causing them to collapse.
Use this database below to check for sinkholes in any Florida county - just enter your county:
Bobby Deskins, 10 Connects