Texas Speleological Survey

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This page last updated September 13, 2013

Devil's Sinkhole

Click on Map below for a larger image

Click on Map below for a larger image

  • Special Hazards: Large shaft entrance, obscure guano miners' entrances, and loose breakdown, especially near the Lake Room; see Special Instructions for specific details.
  • Length: 329 m (1,081 ft.) 
  • Depth: 107 m (351 ft.) 
  • Author: George Veni

The general public is not allowed to enter the cave, but may view the evening bat flight tours offered by the Devil's Sinkhole Society (DSS).  These tours are usually offered from April through October depending on the presence of the bats.  During the winter months, the DSS offers daytime tours to view the entrance.  Persons interested in attending one of these tours should make reservations through the Devil's Sinkhole Society:

Devil's Sinkhole Society Inc.
101 Sweeten St.
P.O. Box 97
Rocksprings, Texas 78880

(830)-683-2287

DSS website for information on tours and local accommodations:

http://www.devilssinkhole.org/

The interior of the cave is accessible only for scientific work and occasional caving trips by experienced vertical cavers.  TPWD has kept the cave closed due to concerns for safety and bat conservation.  Three people have died in the sinkhole, the first around 1900, the second in 1960, and the most recent in 1972.  Caution and vertical competency are required in and near the shaft at all times.

The Texas Cave Management Association (TCMA) is involved in a cooperative project with the Texas Parks and Wildlife and the Bureau of Economic Geology to create a full 3D reconstruction of the currently accessible major passages of the Devils Sinkhole using non-invasive LIDAR (LIght Detection And Ranging) mapping. This would be one of the first and the most complete subsurface model for any park facility at the federal or state level.

Description:

The Devil's Sinkhole is one of the premier caves of Texas and among the legendary classic pits of the U.S. The cave is a immense 20-30 m diameter shaft that drops 42 m (138 ft.) into a room measuring more than 100 m in diameter.

The huge entrance to this National Natural Landmark is somewhat obscure because it lies flat in a flat upland of the Edwards Plateau-some people have nearly driven into it! The shaft entrance is about 14 m in diameter and is sharply undercut to a diameter of more than 25 m. About 34 m down the pit, it suddenly opens into an immense room measuring 138 m long by 76 m wide. While many find the sharp lip of the shaft tricky to negotiate, it provides a free-hanging 42 m rappel acclaimed as the finest in the state. The rappel ends on top of a breakdown mountain located centrally in the room. The view from the mountaintop is awesome; sunlight illuminates most of the vastness, which extends to a depth of 80 m below the entrance. The room houses one of the larger bat colonies in Texas, so the guano is pervasive and often deep, sometimes hiding small holes or crevices in the breakdown floor. Along the northwest and southwest corners of the room, breakdown has separated some areas into smaller rooms, two of which lead deeper to water. These "lake rooms" have been explored by divers to depths of 11 m without finding any significant passages. The main Lake Room in the northwest corner of the room is accented with speleothems.

Historically, the Devil's Sinkhole is best known for its impressive shaft entrance. Ranchers who discovered the cave in 1876 thought is was "a helluva hole," but their more genteel wives suggested "Devil's Sinkhole" as a less vulgar name. Graffiti carved into rocks at the base of the pit indicates it was descended as early as 1889. Exploration of the cave has run the gamut of vertical technique and technology, including massive wooden ladders, ladders of barbed wire with stick rungs, sheep-wire fencing, winch-powered elevator, car-powered cables connected to seat harnesses and bosun's chairs, prussik knots, cable ladders, and modern single rope techniques. With Texas as the jumping off point for expeditions to deep caves in Mexico, many modern vertical caving techniques were first tried and tested at the Sinkhole.

Over the years the Devil's Sinkhole has been the subject of many expeditions, enterprises, and studies. From the 1950s to the early 1980s, several unsuccessful attempts were made with scuba, gravity meters, and well drilling in hopes of finding adjoining rooms and passages. Films and videos were made in the cave in 1947 and 1989. From the first years of its discovery, the cave has been recognized and used as a resource in many ways: cowboys lusted for honey from bee hives that hung in the shaft; guano was mined intermittently from the cave from at least the 1930s through the 1950s; windmill pipes were laid down into the Lake Room to water-parched cattle; an elevator cage was installed on a boom for a brief commercial period in 1949 and 1950 when visitors could ride up and down the shaft for $1 (the cage can be found on the east slope of the breakdown mountain); and during World War II the U.S. Government sent two young soldiers into the cave to study the bats for possible use in delivering incendiary bombs. The soldiers nearly died trying to climb the rotten old wooden ladder, and had to be hoisted out on a rope.

In 1985, the Texas Parks and Wildlife Department purchased the cave and surrounding 1860 acres from the Whitworth Estate and opened the area to limited public access in 1992 as a State Natural Area.  Since that time, there has been little visitation within the cave due to liability concerns and to preserve the cave's ecosystem.  Since May 2002, the Devil's Sinkhole Society (DSS), a group of volunteers working as concessionaires for the TPWD, have organized guided tours to view the evening bat flights and daytime tours to view the entrance.  The DSS has a museum and gift shop at the Rocksprings Visitors Center in downtown Rocksprings, Texas.

In addition to the cave's famous pit entrance, the Devil's Sinkhole is also well known for its large bat colony. The colony seasonally varies from 30,000 to 1 million Mexican freetails (Tadarida brasilien-sis mexicana), the ninth largest freetail colony in Texas. Four other bat species have also been identified at the cave. In 1958 the bat colony was estimated at 6 million. Like other Mexican free-tailed bat colonies in Texas and the southwestern U.S., the sinkhole yields an outstanding nightly spectacle as the cloud-like mass of bats spiral outward for dinner. Their dive-bomb morning return is equally thrilling. While the bats catch most of the attention, cave swallows and other birds also share the pit, and the cave has a rich invertebrate fauna consisting mostly of guanophiles. Troglobitic isopods, Cirolanides texensis, and an endemic troglobitic species of amphipod, Stygobromus hadenoecus, have been found in the lake rooms.

Geologically, the Devil's Sinkhole is simply a big room, the roof of which caved in to form the breakdown mountain. The shaft and most of the room is within the Segovia Member of the Edwards Limestone, while the lake rooms and sumps extend into the Fort Terrett Member. The room formed under phreatic conditions by slow-moving ground-water. As nearby valleys incised and groundwater levels dropped, water drained out of the room. Without the water's buoyant support, the ceiling began to collapse. Vadose water solutionally enlarged some fractures and enhanced the collapse process; vadose seepage can still be seen trickling down the walls of the main shaft. Although the cave's size is unusual, seemingly isolated chambers of this sort are not unusual in the Edwards Plateau region. 

Bibliography:

Byrd, T. 1983. The Devil's Sinkhole: report of exploration, May 7-8, 1983. Unpublished report, 59 pp.

Couffer, J. 1992. Bat bomb, World War II's Other Secret Weapon. Univ. Texas Press, Austin. 252 pp.

Elliott, W. R., and J.R. Reddell. 1975. The fauna of the Devil's Sinkhole. Devil's Sinkhole area-headwaters of the Nueces River. Austin, Univ. Texas at Austin. Division of Natural Resources and Environment. :70-74.

Fieseler, R. G., J. Jasek, and M. Jasek. 1978. An introduction to the caves of Texas. NSS Convention Guidebook, No. 19, p. 93-94.

Foster, F. 1950. The Devil's Sinkhole. 52-minute color and sound film. Video available for rental from the National Speleological Society.

Reddell, J. R., and A. R. Smith. 1965. The caves of Edwards County. Texas Speleol. Surv., 2(5-6):19-28.

Texas Speleological Survey. 1991. Report on the 60 longest and deepest caves. Texas Caver, 36(6):122.

Texas Parks and Wildlife Department. 1990. Down Under Texas. Video for Made in Texas television series. VHS, 28 min. Available from the Department.

Wahl, R. 1993. Important Mexican free-tailed bat colonies in Texas. pp. 47-50 in Jorden, J. and R.K. Obele (eds.), 1989 Natl. Cave Mgmt. Symp. Proc. Texas Parks and Wildlife Press.

White, P. J. 1948. The Devil's Sinkhole. Bull. Natl. Speleol. Soc., 10:214.

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