Cave of the Mounds
Encyclopedia
Blue Mounds, Wisconsin
Blue Mounds is a village in Dane County, Wisconsin, United States. As of the 2000 census, the village had a population of 708. The population was estimated at 766 in 2009. The village is adjacent to the Town of Blue Mounds and is part of the Madison Metropolitan Statistical Area.-Geography:Blue...
, Wisconsin
Wisconsin
Wisconsin is a U.S. state located in the north-central United States and is part of the Midwest. It is bordered by Minnesota to the west, Iowa to the southwest, Illinois to the south, Lake Michigan to the east, Michigan to the northeast, and Lake Superior to the north. Wisconsin's capital is...
, USA, 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 called speleothems. The Chicago Academy of Sciences considers the Cave of the Mounds to be "the significant cave of the upper Midwest" because of its beauty, and it is promoted as the "jewel box" of major American caves. In 1988, the United States Department of the Interior
United States Department of the Interior
The United States Department of the Interior is the United States federal executive department of the U.S. government responsible for the management and conservation of most federal land and natural resources, and the administration of programs relating to Native Americans, Alaska Natives, Native...
and the National Park Service
National Park Service
The National Park Service is the U.S. federal agency that manages all national parks, many national monuments, and other conservation and historical properties with various title designations...
designated the cave as a National Natural Landmark
National Natural Landmark
The National Natural Landmark program recognizes and encourages the conservation of outstanding examples of the natural history of the United States. It is the only natural areas program of national scope that identifies and recognizes the best examples of biological and geological features in...
.
History
The limestoneLimestone
Limestone is a sedimentary rock composed largely of the minerals calcite and aragonite, which are different crystal forms of calcium carbonate . Many limestones are composed from skeletal fragments of marine organisms such as coral or foraminifera....
from which the cave was carved began forming approximately 488 million years ago, during the Ordovician Period. During this time, much of North America
North America
North America is a continent wholly within the Northern Hemisphere and almost wholly within the Western Hemisphere. It is also considered a northern subcontinent of the Americas...
was covered with warm, shallow seas where shellfish
Shellfish
Shellfish is a culinary and fisheries term for exoskeleton-bearing aquatic invertebrates used as food, including various species of molluscs, crustaceans, and echinoderms. Although most kinds of shellfish are harvested from saltwater environments, some kinds are found only in freshwater...
thrived. Over millions of years, the shells they left behind accumulated, forming enormous quantities of limestone. The type of limestone in which the cave was formed is called galena dolomite
Dolomite
Dolomite is a carbonate mineral composed of calcium magnesium carbonate CaMg2. The term is also used to describe the sedimentary carbonate rock dolostone....
because of its high concentration of the lead
Lead
Lead is a main-group element in the carbon group with the symbol Pb and atomic number 82. Lead is a soft, malleable poor metal. It is also counted as one of the heavy metals. Metallic lead has a bluish-white color after being freshly cut, but it soon tarnishes to a dull grayish color when exposed...
ore galena
Galena
Galena is the natural mineral form of lead sulfide. It is the most important lead ore mineral.Galena is one of the most abundant and widely distributed sulfide minerals. It crystallizes in the cubic crystal system often showing octahedral forms...
.
The cave began forming about a million to a million and a half years ago, 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 the water table
Water table
The water table is the level at which the submarine pressure is far from atmospheric pressure. It may be conveniently visualized as the 'surface' of the subsurface materials that are saturated with groundwater in a given vicinity. However, saturated conditions may extend above the water table as...
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, and continues to this day.
The area around the Blue Mounds, Dane County, was first settled in 1828 by Ebenezer Brigham
Ebenezer Brigham
Ebenezer Brigham was a 19th century American pioneer, businessman and politician. He was one of the first Americans to explore southwestern Wisconsin and the first permanent settler in present-day Dane County, Wisconsin...
, a successful lead
Lead
Lead is a main-group element in the carbon group with the symbol Pb and atomic number 82. Lead is a soft, malleable poor metal. It is also counted as one of the heavy metals. Metallic lead has a bluish-white color after being freshly cut, but it soon tarnishes to a dull grayish color when exposed...
miner from Massachusetts
Massachusetts
The Commonwealth of Massachusetts is a state in the New England region of the northeastern United States of America. It is bordered by Rhode Island and Connecticut to the south, New York to the west, and Vermont and New Hampshire to the north; at its east lies the Atlantic Ocean. As of the 2010...
. 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 a trading post
Trading post
A trading post was a place or establishment in historic Northern America where the trading of goods took place. The preferred travel route to a trading post or between trading posts, was known as a trade route....
, an inn, a stagecoach
Stagecoach
A stagecoach is a type of covered wagon for passengers and goods, strongly sprung and drawn by four horses, usually four-in-hand. Widely used before the introduction of railway transport, it made regular trips between stages or stations, which were places of rest provided for stagecoach travelers...
stop, and the first post office
Post office
A post office is a facility forming part of a postal system for the posting, receipt, sorting, handling, transmission or delivery of mail.Post offices offer mail-related services such as post office boxes, postage and packaging supplies...
in Dane County. Ebenezer Brigham later became a colonel and helped build and command Fort Blue Mounds
Blue Mounds Fort
Fort Blue Mounds, also known as Blue Mounds Fort, was located in Blue Mounds, Dane County, Wisconsin, USA.-History:The settlement of Blue Mounds was founded in 1828 by Ebenezer Brigham on the south slope of the eastern mound of the Blue Mounds...
during the Blackhawk 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 accidentally discovered when limestone quarry
Quarry
A quarry is a type of open-pit mine from which rock or minerals are extracted. Quarries are generally used for extracting building materials, such as dimension stone, construction aggregate, riprap, sand, and gravel. They are often collocated with concrete and asphalt plants due to the requirement...
workers blasted a section of the quarry and exposed an opening to the cave. Work at the quarry then immediately stopped and was never continued. Soon after, the cave was closed to prevent damage from curious souvenir
Souvenir
A souvenir , memento, keepsake or token of remembrance is an object a person acquires for the memories the owner associates with it. The term souvenir brings to mind the mass-produced kitsch that is the main commodity of souvenir and gift shops in many tourist traps around the world...
seekers who removed pieces of stalactites and stalagmite
Stalagmite
A stalagmite is a type of speleothem that rises from the floor of a limestone cave due to the dripping of mineralized solutions and the deposition of calcium carbonate. This stalagmite formation occurs only under certain pH conditions within the underground cavern. The corresponding formation on...
s to take home. The cave was reopened in May, 1940, after lights and wooden walkways had been installed. Since then, the wooden walkways have been replaced with concrete ones to accommodate the many visitors. Theatrical lighting has also been installed to further highlight the colors and shapes inside the cave. In 1988, the cave was designated a National Natural Landmark
National Natural Landmark
The National Natural Landmark program recognizes and encourages the conservation of outstanding examples of the natural history of the United States. It is the only natural areas program of national scope that identifies and recognizes the best examples of biological and geological features in...
by the United States Department of the Interior
United States Department of the Interior
The United States Department of the Interior is the United States federal executive department of the U.S. government responsible for the management and conservation of most federal land and natural resources, and the administration of programs relating to Native Americans, Alaska Natives, Native...
and the National Park Service
National Park Service
The National Park Service is the U.S. federal agency that manages all national parks, many national monuments, and other conservation and historical properties with various title designations...
. To be considered a NNL, "a site must be one of the best examples of a natural region's characteristic biotic or geologic features."
Formations
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:- Soda strawSoda strawA soda straw is a speleothem in the form of a hollow mineral tube. They grow in places where water leaches slowly through cracks in rock, such as on the roofs of caves...
s - Soda straws are formations characterized by thin, hollow tubes made of minerals. They have the potential to form into stalactites if the holes at the bottom of them become plugged. - FlowstoneFlowstoneFlowstones are composed of sheetlike deposits of calcite formed where water flows down the walls or along the floors of a cave. They are typically found in "solution", or limestone caves, where they are the most common speleothem. However, they may form in any type of cave where water enters that...
s - Flowstones are created when water travels along a surface and deposits minerals. In limestone caves, flowstones are generally the most common type of formation. - Curtains - These are formed when water droplets run along the ceiling of the cave and gradually form sheets of minerals.
- Lily pads - Lily pads are created when water droplets fall into a puddle and create a formation on the surface reminiscent of a lily pad.
- Helictites - Helictites are an unusual form of stalactite that grow with bends or angles in them that seem to defy gravity. Their strange growth style is most likely caused by capillary forces acting on the water droplets.
- Oolites - Also called "cave pearls", they are a beautiful but rare speleothem. These are spherical formations made when a droplet falls onto some sand and calcite forms around the sand, much like the way a pearl is formed.
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. Somewhere in the cave, there is a large orthoceras
Orthoceras
Orthoceras is a genus of extinct nautiloid cephalopod. This genus is sometimes called Orthoceratites. Note it is sometimes misspelled as Orthocera, Orthocerus or Orthoceros ....
that you can spot
Tourism
The cave is located 20 miles west of MadisonMadison, Wisconsin
Madison is the capital of the U.S. state of Wisconsin and the county seat of Dane County. It is also home to the University of Wisconsin–Madison....
, off U.S. Highways 18/151 in Blue Mounds
Blue Mounds, Wisconsin
Blue Mounds is a village in Dane County, Wisconsin, United States. As of the 2000 census, the village had a population of 708. The population was estimated at 766 in 2009. The village is adjacent to the Town of Blue Mounds and is part of the Madison Metropolitan Statistical Area.-Geography:Blue...
, Wisconsin
Wisconsin
Wisconsin is a U.S. state located in the north-central United States and is part of the Midwest. It is bordered by Minnesota to the west, Iowa to the southwest, Illinois to the south, Lake Michigan to the east, Michigan to the northeast, and Lake Superior to the north. Wisconsin's capital is...
. Since its opening in 1940, the cave has hosted millions of tourists.