No water flows through them now.

They are, in the geological sense, dead — abandoned by the water that carved them, sealed into a condition of extraordinary stasis.

The limestone that forms the cave was deposited at the bottom of a shallow inland sea during the Mississippian period, roughly 330 million years ago.

Marine organisms built it up, layer upon layer, compressing under time and pressure into rock.

Above the limestone lies a protective cap of Big Clifty Sandstone and shale — a geological lid that has kept the upper passages dry and preserved the chemistry that produces the minerals the ancient miners sought.