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Roger Weller, geology instructor

Crystal Cave, Wisconsin
by Steven Hessil
Physical Geology
Fall, 2009

Crystal Cave, Wisconsin

     Crystal Cave is the largest cave in the state of Wisconsin and is enjoyed by 40,000 guests from around the world every year.  A local farm boy named William Vanasse stumbled upon this cavity in 1881 while out exploring.  In its original state it was filled with much debris and the immense size was not suspected.  After many decades of excavation the cave was opened to the public in 1942.  The cave itself stretches for nearly a mile underground, though only a portion of this expanse is open to the public, and newfound openings show a possibility of another large portion yet unexcavated.



     When exploring the cave a newly christened spelunker will be 70 feet below the surface at most points.  The sedimentary rocks forming the cave are known as the Prairie du Chein formation, and there are also small amounts of flint and “bog iron” present. This formation is found throughout the Midwest in the states of Illinois, Wisconsin, Michigan and Indiana.  Three separate distinct layers are evident within Crystal Cave and each has its own specific texture.  These layers are composed of limestone and dolostone created in a deepwater environment, sandstone composed in a shallow water environment, and a thick layer of dolomite respectively.  The estimated age of the Prairie du Chein formation is 485 million years old.  

Cave Formations

     Within Crystal Cave there are different formations.  It is full of your basic stalactite and stalagmites. The most widespread and interesting formations within the cave are that of soda straws.  These stalactites are formed when calcium bicarbonate reaches the cavern and is exposed to air and becomes calcium carbonate forming calcite. Soda straws are interesting because they have a hole in the center of the formation resembling a straw.  Flowstone is
also present within the cave.

vacation 2009-6-19 crystal cave 10h by mrsleise.

Stalactites and Stalagmites

     Stalactites are formed by rainwater seeping its way through soil.  As the water seeps through the soil it picks up small amounts of limestone and carries it downward. Upon reaching the roof of a cave the water evaporates leaving behind the small amount of limestone on the cavern ceiling.  On the other hand, if the water does not have time to evaporate then it will drop off of a formed stalactite and impact the floor of the cavern.  Soon enough it will evaporate and leave behind the same trace amount of limestone, thus forming a stalagmite.  This is also the reason why stalagmites generally grown directly underneath a stalactite. 

vacation 2009-6-19 crystal cave 11h by mrsleise.


     Flowstone is created in much the same way as stalactites and stalagmites except it is produced while water is flowing down the walls of a cave.  This gives the formation a very distinct pattern. Also, often there are other minerals within the water along with the limestone and they can produce different colored formations, including; red from rust, green from copper, grey from aluminum oxide, and white from pure calcite.

How are caves formed?

     Caves are formed when water mixed carbon dioxide and forms carbonic acid.  The carbonic acid then runs through a fracture in a jointed rock and begins to erode it.  When the carbonic acid dissolves limestone it then produces a calcium bicarbonate solution.  Moving water is needed throughout the process to move the carbonic acid and continue erosion.  This process is very slow, in reference to human time, and often takes tens of thousands of years to produce a cave of any size at all.

Crystal Cave, Spring Valley, Wisconsin by profkaren.

 Cave Inhabitants

     Bats populate Crystal Cave during the winter months.  They often enter the cave during October or November to hibernate and leave again during April or May.  Bats are extremely active during the summer months and can eat up to three thousand insects in a single night.  There are three separate species that inhabit the cave, including; The Little Brown, the Northern Myotis, and the Eastern Pipistrelle.


Works Cited:


IMG_2392.JPG by Staisey & Phil.