Devil's Hole Cave, Allegany County
Devil's Hole Cave is developed in the Keyser Member of the Helderberg Limestone. The major passages follow strike joints along the same general strike of the synclinal structure which extends to the southwest towards Twiggs and Horse Caves, with interconnecting passages being developed along the dip of the beds at the same inclination. Passage cross-sections are controlled by both bedding and joint plane intersection. The dip averages about 40º southeast, strike N. 35º east.
Devil's Hole Cave is one of the largest and most interesting Allegany County caves. The entrance is a narrow 12-foot shaft in the bottom of a large sinkhole which represents the head of a deep gully. During wet periods a small stream flows in this gully and seeps into the cave just before reaching the entrance.
Devils Hole appears to be a combination of two different caves. The entrance shaft drops into an actively eroding stream passage which trends downdip for about 200 feet, while dropping 100 feet in a series of small waterfalls and cascades to end in a siphon-crawl. The stream passage is typically a narrow fissure 10 feet to 30 feet high, but lowers gradually to a point which evidently floods to the ceiling occasionally. The stream generally ceases flowing in the summer.
Midway through its course this passage intersects at two points large passages constituting an upper level. These passages run roughly parallel and interconnect by narrow tubes or conduits which are inclined along the dip of the beds. They extend to the northeast for 60 to 100 feet but end in breakdown and clay fill. To the southwest (towards Twiggs and Horse Caves) and down gradient they encounter a series of four major tubes or conduits inclined at about 40º which slope down into a large trunk which is an abandoned stream channel. This old stream channel is typically 10 to 15 feet in diameter and is gravel floored. This passage is about 50 feet below the entrance (but still above the present stream, which may have served to pirate or behead this original watercourse). Large pieces of break down occur throughout this passage, as well as in the rest of the cave. The southwest end of the trunk terminates in a gravel and sand stream deposit which blocks the passage. Two of the "feeder tubes" encountered in the trunk passage may be followed updip through prodigious amounts of wet mud and small pools to an extension of the first upper level passage. Several vertical domepits ranging from 25 to 40 feet high are developed here. Fossil corals (Favosites) are exposed in the base of the largest one. Speleothems are rare in Devil's Hole, but occur in scattered places as beautiful flowstone-covered walls and the usual stalactites and draperies. Slightly over one-fourth mile of passage was mapped in 1969.