Fog in a cave? It’s so underground…⁣ ⁣ This week a large storm came through Mammoth Cave which caused a quick drop in the temperature. This pressure change caused the airflow to reverse, pulling into the cave resulting in a dense fog filling the Rotunda room. The large circular room is the sixth-largest room of the cave and is about a quarter-acre in size. It measures 140 feet wide and about 40 feet from floor to ceiling. This occurrence happens infrequently, only with the perfect conditions between the surface and cave. After about 10 minutes, the fog dispersed. ⁣ ⁣ Image: Swirling fog forms on the ceiling of the cave at @mammothcavenps ⁣ ⁣ #mammothcave #kentucky #cave #underground #cavesandkarst #foggy