Existing comment:
A Roof Over the Cave:
In the Pennsylvania Period, 280 million years ago, a layer of sand and silt was laid down by an ancient river delta, forming the slanted layer of mixed sandstone and shale visible immediately across this ravine.
Beneath this "caprock" lie 600 feet of layered limestone deposited as an ancient sea bed some 350 million years ago. The miles of cave passageway that make up Mammoth Cave are found within these layers.
Sandstones and shales are more resistant to being dissolved by water then is the limestone beneath. This caprock of sandstone and shale acts like a roof, shedding water to the side of the ridge. |