Existing comment:
A Natural Entrance:
Hundreds of miles of cave form in the limestone, layers beneath the sandstone and shale caprock as water in underground streams flows to the Green river.
Surface streams also flow to the Green River, and begin to erode the sandstone and shale caprock.
The surface stream cuts down into the more easily dissolved limestone, forming a ravine.
The surface stream's ravine deepens and intercepts the underlying cave passage. The passageway's collapse opens the cave to the outside world. |