| Cave of the Mounds | |
|---|---|
 Inside Cave of the Mounds | |
| Location | Blue Mounds,Wisconsin |
| Coordinates | 43°01′05″N89°48′58″W / 43.018°N 89.816°W /43.018; -89.816 |
| Designated | 1987 |
| Website | Official website |
Cave of the Mounds, a naturallimestone cave located nearBlue Mounds,Wisconsin, United States, is named for two nearby hills called the Blue Mounds. It is located in the southern slope of the east hill. The cave's beauty comes from its many varieties of mineral formations calledspeleothems. TheChicago Academy of Sciences considers the Cave of the Mounds to be "the significant cave of the upper Midwest" because of its beauty,[1] and it is promoted as the "jewel box" of major American caves.[1] In 1987, theUnited States Department of the Interior and theNational Park Service designated the cave as aNational Natural Landmark.[2]
Thelimestone from which the cave was carved began forming approximately 488 million years ago, during theOrdovician Period.[3] During this time, much ofNorth America was covered with warm, shallow seas. Over millions of years, calcium carbonate shells from tiny marine organisms accumulated on the sea floor, forming enormous quantities of limestone. The type of limestone in which the cave was formed is calledgalena dolomite because of its high concentration of thelead oregalena.
The cave began forming about a million to a million and a half years ago,[4] in a manner similar to many caves. A large crack in the surface of the rock, called the cave's "lifeline", allowed rain water to seep into the stone. In the air, rain combines with carbon dioxide to form a weak carbonic acid. Though this acid is not very strong, it is strong enough to dissolve away the limestone after it seeps in through the "lifeline". Over time, large cavities were dissolved in the stone and as thewater table dropped, the water drained out and the cavities filled with air. Now that the cavities are filled with air instead of water, the water droplets coming from the "lifeline", which are saturated with dissolved calcium carbonate, deposit solid calcium carbonate, which builds up over time to create speleothems. This is a very gradual process, usually taking 50 to 150 years to form one cubic inch of material,[4] and continues to this day.
The area around the Blue Mounds,Dane County, was first settled by Europeans in 1828 byEbenezer Brigham, a successfullead miner fromMassachusetts. He had traveled to Wisconsin to join in the lead rush of the late 1820s. After arriving, he set up operations just north of where the cave lies today. Ebenezer's house later became atrading post, aninn, astagecoach stop, and the firstpost office in Dane County. Ebenezer Brigham later became a colonel and helped build and commandFort Blue Mounds during theBlackhawk War. He died after a long life, not knowing that a beautiful cave existed beneath his Brigham Farm.
On August 4, 1939, Cave of the Mounds was discovered accidentally when limestonequarry workers blasted a section of the quarry and exposed an opening to the cave.[3] Work at the quarry then immediately stopped and was never continued. Soon after, the cave was closed to prevent damage from curioussouvenir seekers who removed pieces ofstalactites andstalagmites to take home. There are still foot-sized holes in the flowstone left by these early explorers. The cave was reopened in May, 1940 under the supervision ofAlonzo W. Pond after lights and wooden walkways were installed. (Pond'sIllustrated Guidebook of the Newly Discovered Cave of the Mounds (1941) was the first speleological publication about the cave, written primarily for tourists.)[5] Since then, the wooden walkways have been replaced with concrete ones to accommodate the many visitors. Theatrical lighting, original design byGilbert Vaughn Hemsley Jr.[6] has also been installed to further highlight the colors and shapes inside the cave. In 1987, the cave was designated aNational Natural Landmark by theUnited States Department of the Interior and theNational Park Service. To be considered a NNL, "a site must be one of the best examples of a natural region's characteristic biotic or geologic features."[7]
Cave of the Mounds is home to many varieties of speleothems. As with most caves, stalactites and stalagmites are common. Formations found inside the cave include:
These formations come in many different brilliant colors such as reds, browns, blues, and grays. The reds and browns are caused by the presence of iron oxide in the formation. Similarly, blues and grays are caused by manganese oxide. Some speleothems are even partially luminescent and give off light for a brief period after exposure to another light.
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Because the cave was underground before humans discovered it, animals likebats are not usually found in this subterranean environment. Despite this, a number of organisms that were small enough to seep through cracks in the ceiling populate the cave.[7][4]
The cave is located 20 miles west ofMadison, off U.S. Highways18/151 inBlue Mounds,Wisconsin. Since its opening in 1940, the cave has hosted millions of tourists.[4]
