The underground river.
About 10 million years ago, there was a river flowing atop the Big Clifty sandstone. It found a hole and entered the underlying limestone. There it started dissolving the limestone, and relocated below the surface. Our entry sink hole is one place the water entered, also in areas located along the Lake Trail.
As we continued to be raised above sea level, the water table dropped, and the river dug lower into the limestone, ending near the lake level. Erosion caused the river source to disappear. Water from the Imagination Room carved the Wedding Chapel. Subsequent deposits of flow stone closed up the water channels.
The sandstone was eroded away, and water could flow through the limestone. Once the cave was exposed to air, the water couldn’t hold as much calcium and it started to be deposited as our beautiful secondary formations.