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Below are answers to questions commonly asked about the cave.
For information about the tour experience see Preparing
For Your Tour.
How far underground are we?
Distances from floor of Cave to surface above:
- South Cave Onyx Ridge - 48 feet
- South End - 42 feet
- Meanders - 70 feet (at the red light)
- North Cave - 57 feet
- North End Collapse - 43 feet
- Bypass Tunnel - 40 feet
How far is the water table below the Cave?
The water table is roughly 400 feet below the surface. The water
table is very slowly lowering as area rivers erode the surface.
The local water table is controlled primarily by the Wisconsin
River to the North.
Is the Cave privately owned?
Yes, and it has been since the day it was discovered. The Cave
is on Brigham Farm, which was founded in 1828 by Ebenezer Brigham, the first european settler in Dane County. When he passed on, he left the property to his great nephew Charles Brigham, Sr. Charles and his family operated the property primarily as a dairy farm, but occasionally leased quarry rights to local contractors, and thus in 1939 the Cave was discovered! In 1988, Cave of the Mounds earned the National Natural Landmark designation, entering into a public-private partnership with the National Park Service. This partnership ensures that the Cave will be managed & protected for future generations as a prime example of Wisconsin's Natural Heritage.
What causes the different colors in the Cave?
The mineral calcite is white. Calcite is the primary mineral that you see in the Cave because it is essentially limestone that has been dissolved and redeposited. Reddish brown colors come from iron oxide, or rust.
Shades of black, purple, blue and
gray come from manganese oxide. Iron and manganese are present within the limestone that surrounds the Cave. When these two minerals mix with water and air (oxygen), an oxidation reaction occurs, leaving behind the beautiful hues.
Are there any animals that live in the Cave?
Most people think of bats, blind fish, and big scary insects when they picture a cave. Don't worry, our Cave does not house any of these critters! However, we do have one creature specially adapted for life in the dark zone of our Cave. It's a tiny flea-like insect called a springtail. They are typical troglobites - they complete their entire life cycle and never leave the cave environment. Springtails in our Cave feed on naturally occurring bacteria - gallionella (product of iron oxide) and leptothrix (product of manganese oxide) - that help create the beautiful colors in the cave formations. In 1958, world renowned speleobiologist Ken Christiansen and his team identified the springtails that live in Cave of the Mounds as Sinella coecobrya tenebricosa.
Why aren't there any other animals in the Cave?
Bats, coyotes, raccoons, and other trogloxenes that might have used the Cave for shelter would have needed a natural opening to enter and exit through. Before Cave of the Mounds was discovered in 1939, it was a closed system. That means, there were no natural openings from the Cave to the surface above, keeping it hidden for millions of years. Most caves are discovered via a natural opening created by a sinkhole or other natural occurrence, so this unique status distinguishes Cave of the Mounds from other show caves in Wisconsin.
If there are no natural openings, how does air get into the Cave?
Limestone is a porous rock, so air and water pass through it fairly
easily. As the barometric pressure changes outside, air passes
through the limestone to compensate for the change, thus either
drawing air into the Cave or pushing it out. However, most air
circulation is through the blast opening or the mine shaft in the exit tunnel.
When were the tunnels, steps, and walkways constructed?
When Cave of the Mounds was opened to the public in May, 1940, the stairs, walkways, and handrails were made of wood. Construction of the tunnels, cement walkways and steel handrails that visitors use today was started in the mid-1940's and was finished by 1958. The Exit Tunnel was finished
in 1948, and the present Cave Entrance Building was constructed in 1942.
How long is the Cave?
The total surveyed length of the Cave (lengths of the caverns,
Meanders, and every nook and cranny added together) is 1692 feet.
The straight-shot length of the caverns, from the "South
End" to the very end of the "Dream River"
(as the bat flies) is approximately 750 feet. We walk about 1/5
of a mile (about 1100 feet) on the tour.
Are there current efforts to find more cave passageway?
Three methods for finding caves are seismic soundings, resistivity
testing, and gravity measurements. However, due to the sensitivity
of the equipment, such testing can be extremely expensive. Also,
it is very difficult to determine the size of underground cavities
using surface testing. Gravity testing has been done around Cave
of the Mounds; and more recently seismic soundings were tried
above the Song of Norway grounds. The Wisconsin Speleological Society has done several digs in the Meanders area of the Cave. They are basically following the natural flow of water as it moves through the Cave on it's journey to water table several hundered feet below.
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