A knowledgeable guide hosts visitors in the “Big Room”, part of an interesting, one-hour visit of the Seneca Caverns. This room (above) is on the formation’s fourth, sub-surface level. In the lower photo, lady friend Sue Brooks—laughing top right—enjoys Rich Hatfield’s exploration of the cave's “Ole Mist’ry River, 110 feet below ground. The legs (center) belong to Mrs. Hatfield.

SENECA CAVERNS—
One of Ohio’s Largest

In 1872, two youths hunting rabbits discovered what is now known as the Seneca Caverns when their pooch fell through a sink hole in the brush about four miles southwest of Bellevue, OH.

That dog led rescuers to the discovery of the interconnected upper four levels of the seven levels open to visitors today.

The absence of man-made artifacts from prior to the late 1800s suggests the caves were not commonly known to earlier residents of Northern Ohio.

Once thought to be the result of an earthquake*, current studies suggests the cave is the result of simply timeless motion along a fault line—a boundary between the Earth’s tectonic plates.

That motion would cause the underground rock strata to crack and sometimes collapse causing the cavities.

These underground cavities or levels likely were enlarged by ground water moving vertically and laterally through the various planes of the fault line.

Today, visitors descend more than 100 feet through seven levels until they encounter the “Ole Mist’ry River” which marks the bottom of the normal cavern tour.

The water level in the cave can change dramatically. The lowest water level was observed in 1934 when it dropped an estimated 100 feet below the seventh level exposing an additional five rooms.

Even at that depth the fracture could be seen through the crystal clear water descending ever lower. The absolute bottom of the cave structure has never been determined.

In July of 1969 the cavern was filled with ground water after nine inches of rain fell during four hours. It took two days for that rain event to fill the cave—and it took four months for the water to return to its normal level.

This underground “river”, commonly referred to as the water table, drains into Lake Erie, some of it passing through an old tourist attraction in Castalia, OH known as the Blue Hole. This was discovered when a note in a closed bottle, dropped into the cave’s underground river, emerged there.

Tours of the cave take approximately one hour and you will want to dress for rigorous activity. You will be descending and climbing the equivalent of a 10 story building on an irregular, rocky, sometimes narrow, path.

And, take a jacket. The underground temperature is a constant 54 degrees.

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Reference
https://kb.osu.edu/dspace/bitstream/1811/23402/1/V090N4_106.pdf
http://www.senecacavernsohio.com/

*An earthquake is the result of the sudden release of built-up pressure along a fault line.

Photo data: Both pictures were done with available light. The exposures were 6/10 second at f/5.6 and ISO 400. The camera was hand-held but solidly supported on a rock or pushed firmly against a cave wall surface to avoid camera shake.