We have had numerous instances of sinkholes appearing in and around my county this week. They have threatened homes, swallowed cars and trees and made some roads impassable. The newest one appeared today right in the middle of Interstate 4! We have even had sinkholes open up in the middle of orange groves and strawberry fields. The sinkholes have been attributed to the freezing cold weather we have had. As it warms up and things begin to thaw we may see even more. By the way- they are not just in my county (Hillsborough) but in neighboring counties as well. That made me research exactly what causes sinkholes:

Sinkholes are all about water.

* Water dissolved minerals in the rock, leaving residue and open spaces within the rock. (This is called "weathering".)
* Water washes away the soil and residue from the voids in the rock.
* Lowering of groundwater levels can cause a loss of support for the soft material in the rock spaces that can lead to collapse.
* Changing groundwater gradients (due to removing or introducing water to the system) can cause loose material to flush out quicker from the voids and the surface to collapse in response.
* Any change to the hydrologic system (putting more water in or taking it out) causes the system to become at least temporarily unstable and can lead to sinkholes.
* Sinkholes can result from seasonal changes in the groundwater table, freeze and thaw of the ground, and extremes in precipitation (drought vs heavy rain).

Sinkholes are always a threat when we experience droughts. I just never realized freezing could cause them too.