Is a sinkhole just a hole in a rock?
I found a really good site from the Department of Environmental Protection in Pennsylvania on sinkholes and what causes sinkholes to form. I especially found the portion on “what is a sinkhole” or “what is sinkhole activity” well-written and worthy of quoting here:
A common misunderstanding is to think that a sinkhole is the hole in the rock. Actually, the sinkhole is what we see on the ground surface because of the hole in the rock below. The space in the rock (known as a void, solution cavity or cave) takes hundreds or thousands of years to form. Then soil from above can move into the void in rock. If the soil is sticky, a void can form within the soil. As more soil washes down (over years or maybe just days), the void space moves toward the surface until it can’t hold together anymore. When it collapses (or subsides), you see the sinkhole on the surface. Often, you can only see soil in the hole and not the actual hole in the rock itself because the rock is too far below.
Pennsylvania sees a lot of sinkhole activity due to the amount of mining activity taking place there, much like what has happened in Polk County. The subsurface is very similar to our counties in Hernando, Pinellas, and Pasco, with a shallow limestone impacted by the movement of what over the limestone.
Have a burning question you’d like to ask about sinkholes? Let us know.