Gorman Cave Click on Map below for a larger image
Description: Gorman Cave, in Colorado Bend State Park, probably is the most-visited noncommercial cave in Texas -a nice stroll in large passage with a shallow stream. Despite being familiar to many, most do not know that Gorman is a very important cave. Just a few meters from the Colorado River, it apparently was formed in the phreatic zone -- the area of the underground where rock aquifers are still full of water. However, the cave shows evidence that it was later filled or nearly filled by clay and gravel. Still later, the Colorado river intersected and downcut into the cave, essentially draining the water from the cave. It thus provides evidence of how the watertable in Texas has shifted over geologic time, and what happens when that happened. Gorman Cave is a resurgence for water that probably comes from nearby Clark's Branch Well Cave, but the cave also back-floods when the river rises. Vadose modification has occurred from both of these sources -- that is, the rock above the aquifer level has been dissolved or otherwise etched to enlarge voids in it. The entrance is quite scenic, being located in a bluff on the west side of the Colorado River. A narrow, steep-sided gully leads from the 5-m-wide, 3-m-high mouth to the river. The walls inside are marked by massive calcite crystals. About 25-30 m inside is a second entrance on the left, which has been enlarged several times by cavers. After another 25 m one encounters a series of travertine dams and pools in which fish are occasionally found after being washed in by the flooding Colorado River. The cave continues in the same manner for another 100 m with gravel floors, pools, short side passages, and travertine.; One wades through a low place, then pops into the Big Room, which is 5 to 10 m high, 5 to 10 m wide, and about 45 m long.
Just beyond the Big Room, the cave is gated. No one may travel beyond the gate except under permit for exploration or scientific studies. To the left is a steep slope up, which ends in the Mouse Hole, a small room that often contains bats. Beyond the gate, the cave narrows to a gravel-floored tube 3 m in diameter. A hole down to the lower stream level is soon seen, followed by Separation Lake, 70 m from the Big Room. This lake is sometimes dry. After 25 m the cave seems to end in a breakdown area, but several holes in the floor lead down to the stream and a narrow squeeze ahead leads to a muddy passage. One crawls and walks through 100 m of gooey mud, passing a small maze on the way. One is now in the area just before "The Crack," an upper level maze and an upward sloping side passage where bats sometimes roost. The Crack has an upper and lower route. Both are knee-to-waist-deep in mud and water. Beyond lies the Bat Room and thick, fungus-covered guano. At this point many cavers begin panting from the worsening air. A steep slide from the Bat Room leads to a T-shaped junction. To the left one goes 30 m to the lower level stream again, a small, dangerous crawl. From the T-junction the right-hand passage leads 25 m to another lake, then CO2 Alley. This passage is 3-5 m in diameter and has a nice gravel floor. It meanders for about 175 m to the first sump. After 50-60 m of water-filled passage there is a 50-m-long air-filled passage that ends at a second sump, which has not been explored. Despite being a relatively easy cave, the back parts of Gorman are notorious for having "bad air." William R. Elliott studied oxygen and carbon dioxide levels in Gorman and other caves on several occasions. Oxygen levels at the end of the cave were as low as 15% (20.9% is the normal atmospheric concentration) while carbon dioxide was as high as 6%. Such conditions can cause headaches, rapid panting, loss of judgment, joint pains, and sickness. The air gets gradually worse from the entrance to the end, but most cavers do not notice it until they are in the crawlways about halfway back. Even worse levels were found in nearby Gorman Falls Cave (Bad Air Hole). Many caves in the Ellenburger Limestone have bad air, which makes pit caves especially hazardous, because people can climb down into the pit and into a pool of carbon dioxide that they cannot breathe, which can lead to hyperventilation and in some cases death. The air is worse during the summer and fall and better in the winter and spring. Some cavers report that the air in Colorado Bend caves becomes worse during wet periods and better during dry periods. The carbon dioxide may emanate from deep geochemical sources in the Gorman Formation (Ellenburger Group). Groundwater and cold fronts may modulate the amount of carbon dioxide in the caves. Further study of this phenomenon is needed. Gorman contains a colony of cave myotis bats, which is partially protected by an iron bat gate, installed past the Big Room in 1992. However, bats may be found almost anyplace in the cave. During the late spring the Big Room is a roost for a maternity colony, so visitors are warned not to enter there at that time. The entrance area occasionally has a few eastern pipistrelle bats. The cave also contains many invertebrate species. The most interesting is Texanobathynella bowmani from stream gravels, known only from Gorman Cave and Roaring Spring, Garza County. Pale crayfish in the stream are the eyed surface species Procambarus simulans. There are two troglobitic amphipods, Stygobromus bifurcatus and S. russelli, and the amphipod Caecidotea biseta. Terrestrial troglobites include the spider Cicurina sansaba (known only from Gorman), and the millipede Cambala speobia. During the summer, large societies of daddy longlegs harvestmen, Leiobunum townsendii, occur on the walls of the second entrance room. Bibliography: Elliott, W. R. 1986. Preliminary atmospheric and biological observations in Gorman Cave and Gorman Falls Cave, San Saba County, Texas. Report to Texas Parks and Wildlife Depart. 6 pp. Elliott, W. R. 1993. Baseline cave ecology, Colorado Bend State Park, Texas: July-November, 1993. Report to Texas Parks and Wildlife Dept. 22 pp. Elliott, W. R. 1994. Air monitoring during construction of a cave gate. 1993 Natl. Cave Management Symp. Proc., Carlsbad, New Mexico. American Cave Conservation Assoc. Kastning, E. H., Jr. 1983. Geomorphology and hydrogeology of the Edwards Plateau karst, central Texas. PhD diss., Univ. Texas, Austin. xxxi + 656 pp. + 6 pls. Reddell, J. R. 1973. The caves of San Saba County. Second Edition. Texas Speleol. Survey, 3(7-8):127 pp. Revised 7/2014; original page author: William R. Elliott. All rights reserved. |
