THE ORIGIN OF CRYSTAL CAVE
The small stream issuing from Crystal Cave as a spring, about ten feet below and fifteen feet east of the main entrance, joins Cascade Creek almost on grade a short distance below. A similar stream issues from the opposite side of the creek a short distance upstream on approximately the same level. This latter stream evidently is draining a cave system which probably was continuous with Crystal Cave in times past. However, due to slumps and collapse of the marble, it is not open to inspection. It is suggested that the major portions of this once continuous cave system were dissolved out and carried away before Cascade Creek valley was lowered to this level, thus bisecting the cave system and giving rise to these water-table streams flowing from opposite directions. After the cave galleries were dissolved out, there is evidence that most of them became filled with clay, sand and gravel. (2) Most of this fill subsequently was washed out, but some of the side chambers still retain a compact, reddish clay reaching almost to the ceiling in some cases. Deposits of gravel contain stream worn boulders up to ten inches in diameter. There are remnants of the fill on the highest shelves in the largest room in the cave, and some of the narrow passages are still tightly filled to unknown depths. These stream gravels are not in accord with the volume or plan of the present stream, and indicate that the larger depositing stream which the cave at one time contained mainly followed two passages to the lower gallery through which the cave is entered. It is interesting to note that similar deposits were reported in sub-water table caverns in the Tennessee Valley. (19) Most of the network of side chambers and passages were not filled with gravel, and their bedded clays indicate that relatively quiet water filled them when the clay was deposited. Some of the clay deposits are capped by a thick layer of flowstone. Perhaps a tight clay fill prevented the latter aggrading stream from entering these recesses to leave coarser materials. There are gravel deposits in the cave which are separated by at least three layers of flowstone, indicating that the stream which laid them down fluctuated considerably from time to time, since flowstone forms slowly, depending upon evaporation. The gravel was exposed successively for a considerable length of time before the stream returned repeatedly with new loads. In the Dome Room and other parts of the cave, there are intricate patterns on the otherwise flat ceilings. Remnants of marble hang down in great profusion and an interesting network of channels, many of which are filled tightly with stream-deposited wastes, have been incised upward into the ceiling. These have been interpreted as having been dissolved by water flowing against the ceiling on a rising fill. (2)
Directly upon entering the Dome Room from the Organ Room, there are some interesting inverted potholes or cone shaped extensions in the ceiling. It is difficult to explain these features except on the assumption that water completely filled all spaces when they were formed, otherwise the presence of air would seem to have prevented their upward growth. (2) Some of them are over seven feet deep.
Streams normally are characterized by a branchwork of tributaries feeding into main channels, but the principal maze of network constituting Crystal Cave is so variable in grade and plan that it must have had a phreatic origin. It seems improbable that a stream could have produced this pattern. (8) There are so many inter-connecting passageways and loops with grades so inconsistent that no free flowing stream could follow them. Some channels resemble syphons and could have supported a stream only under pressure. In many parts of the cave there are patterns on the walls and ceilings which resemble ripple marks in sand. In 1925, Judge Walter Fry noted that the roof in Marble Cave was "heavily grooved and fluted." (12) It has been shown that these flutes record the direction of stream flow, and that they are elongated in the direction of flow. (18) Since they commonly occur on ceilings, they probably were dissolved out by moving water. Some of them have an upgrade both on walls and ceilings, consequently sub-water table streams moving under hydrostatic pressure appear to be the best explanation for them. (2) The same argument may be applied in the Junction Room and other places in Crystal Cave where the flutes change from a downward to an upward trend. A normal free flowing stream could not have made them.
In the Dome Room, as well as in several inter-connecting passageways behind it, there are partitions and thin bladed extensions of marble such as the Elephant Head. Many of these have jagged holes dissolved through them. In several places multi-legged pedestals with sharp, jagged edges rise from the marble floors. There are some passageways that terminate in blind ends. Natural bridges of rough marble across high, narrow passages are not uncommon. The marble literally is honey-combed in places which could not be explained on the basis of stream wear. They appear to have been eaten out when all spaces were completely filled with water.
There are many tubes in the cave, most of which are roughly circular. They extend from horizontal to vertical. One tube about three and a half feet in diameter terminates on the ceiling of Marble Hall, extending upward at a steep angle. On the outside of the cave, about 100 feet above and east of the main entrance, there is a small opening in slumped marble. Behind the slump this becomes a rudely circular tube six feet wide and five feet ten inches high above a partial filling of soil. The tube descends into the mountain at an angle of about six degrees, and at twenty-eight feet from the entrance it turns sharply to the left and narrows to four feet eleven inches in diameter, and forty-two inches high above the fill. From this point on the fill rises almost to the ceiling. Flutes on walls and ceilings indicate a downward or in-leading current of water formerly flowed through it. There is no possible way this tube could have originated under present conditions, terminating on the Valley side and pointing upward about one hundred feet above Cascade Creek. Like many other parts of the cave, it is much older than the valley of Cascade Creek and was exposed by the downward cutting of the stream. It has never drained into Cascade Creek. On the Cave Creek side of the ridge at about the same altitude, there is a jagged shaft descending straight down for a distance of fifteen to twenty feet. There is no evidence that it ever supported a stream, although it communicates with the main cave system. It, too, is a pre-existing part of the cave.
Much additional evidence exists to support the supposition that Crystal Cave is largely phreatic in origin, and that it has been modified and enlarged by a variable stream. As additional studies are made, it is hoped that a more precise and complete interpretation can be made which will include the history of all the known caves in the park.
Last Updated: 31-Jan-2007