Why the ground drops in Tallahassee
Limestone under the south side. South of the Cody Escarpment lies the Woodville Karst Plain. A thin layer of sand covers limestone that slowly dissolves in rain water. That leaves gaps in the rock. Sand can wash down into them, and the ground above sinks.
Real sinkholes happen here. In January 2020, a sinkhole opened at a mobile home park on Capital Circle Southwest in Tallahassee. News reports said it forced two families out and split a trailer. Crews filled it with dirt.
Even lakes drain here. Every decade or two, Lake Jackson, north of town, drains into the rock below through a sinkhole called Porter Hole Sink. WFSU reported one of these drain-outs in 2021. It shows how much open rock sits under parts of Leon County.
The state keeps a list, but most are not checked. The Florida Geological Survey keeps a record of reported dips and holes. It says most reports have never been checked in the field, so the cause is not known. A report on the list does not prove a sinkhole, and a missing report does not prove the ground is safe.
Many dips are not sinkholes. The Florida Geological Survey lists other causes that look the same:
Rotting stumps
And buried wood
Buried trash
And building scraps
Broken sewer or drain pipes
Old septic tanks
That were not filled in right
Loose fill soil
That was not packed down
Clay or organic layers
That shrink as they dry out
Rain after drought. The state says sinkholes are most active when heavy rain follows a long dry spell. Heavy loads and big earth-moving jobs can also set them off.