Why do sinkholes sometimes appear suddenly after storms or droughts?

Many sinkholes form in regions of soluble rock such as limestone, where groundwater slowly dissolves underground channels and caves. Heavy rainfall can change groundwater pressure and erode support, while drought can lower water tables and remove the buoyant support that helped hold loose sediment in place. When the cavity roof can no longer bear the load, it collapses suddenly. Florida and other karst regions have seen dramatic sinkhole events.