Entry into Crystal Cave is only allowed by guided tour. Tour reservations must be made ahead of time and tickets purchased at visitor centers elsewhere in the park. No tickets are sold at the cave, and when tours are being conducted, visitors are not allowed beyond the parking lot without a ticket.
Crystal Cave formed in a ridge between Yucca and Cascade Creeks. This ridge is composed of the Sequoia Roof Pendant, a series of metamorphic rocks within the larger Sierra Nevada Batholith (See Sequoia Roof Pendant EarthCache). One the units found in the ridge is a Jurassic and/or Triassic coarse grained marble sandwiched between quartz biotite schist.
The cave formed in the marble because carbonate rocks, limestone and marble(metamorphosized limestone) dissolve in acid. The acid comes from rain water. As rain falls through the air, it reacts with carbon dioxide along with sulfur oxides, nitrogen, and other natural compounds to form weak acids. As these acids percolated through carbonate rocks, the water slowly dissolves the stone. Weak points along bedding planes dissolve fastest forming cracks. Once the ground water dissolves the cracks to a critical width, the flow of water becomes turbulent increasing the rate that the limestone is dissolved. Even more water is then channeled though these widened cracks eventually creating the caverns.
Many carbonate caves form below the water table where the rock is in constant contact with the water. However, Crystal Cave did not form below the water table. It began forming about 1.15 million years ago as water from Yucca Creek percolated down through the marble exiting on the other side of the ridge into Cascade Creek. The water from Yucca creek first began flowing along the contact between the marble and the adjoining schist. From there, the caves expanded outward into the center of the marble layer.
As the creeks on either side of the ridge eroded further down, the level of cave formation moved down as well. So the oldest caves are above the most recently formed caves. The cave tour enters the lowest and youngest portion of the cave system. The lower levels are through to have formed about 0.56 million years ago.
In addition to the main flow of water from Yucca Creek to Cascade Creek, some water (snow melt and rain water) percolates down vertically through the marble. As this water flows across the cave walls and drops from ceilings a variety of speleothems (dripstone features) began to form. The water that percolated through the marble contains a small amount of dissolved carbonate from being slightly acidic (see the description of that above). When exposed to the air of the cave some of the water evaporates and redeposits the carbonate on the roof, walls, cracks, and floor. Depending upon how the water falls determines the type of speleothem that is made.
Logging requirements:
Send me a note with :
- The text "GC2VWPY Crystal Cave" on the first line
- The number of people in your group (put in the log as well).
- on the tour, how many cave boundary walls are seen and what are they made of?
- Name 2 kinds of speleothems in the cave.
- What geologic event allows the tours to go through the caves without getting soaking wet?
- Find a broken speleothem and determine how thick the outer crust is (NO TOUCHING!)
The following sources were used to generate this cache:
- Joel D. Despain and Greg M. Stock – Geomorphic History of Crystal Cave, Southern Sierra Nevada, California. Journal of Cave and Karst Sudies, V. 67 no 2, p. 92-102.