I’ve had a fascination with caves as far back as I can remember. My first recollection was when I was maybe 4 years old living near Milwaukee.
Dad said we were going to meet some friends in the cavern. I was all excited to begin my first spelunking adventure and was puzzled when we drove up to a building and people were drinking beer inside. My puzzlement turned to disappointment when I learned the difference between a cavern and a tavern.
I hoped when we moved to the family farm when I was 6 that I would discover a cave, but my explorations only revealed a few sandstone ridge overhangs. One of them became like a cave when we covered the opening with branches and gunny sacks. There was only 3 to 4 feet of overhang and only a foot or so in height, but it became our secret hideout.
That didn’t deter my exploration into the underground world. I remember spending two afternoons with my best friend Merle digging around a large slab of rock in the pasture behind the old one-room schoolhouse. I was convinced that the slab was a doorway into the earth. We moved a lot of earth but never found that secret passage
My interest was piqued by the fact that Gullickson’s Glen – a rock shelter where Native Americans visited thousands of years ago leaving behind petroglyphs — was only a few miles away. The carvings may have dated back as far as the Archaic period or 8,000 to 1,000 B.C. I visited Gullickson’s Glen several times to view the carvings.
I never found a cave on our farm, but they are plentiful in Wisconsin. The Wisconsin Speleological Society has documented more than 400 caves that are large enough to explore with thousands more estimated to exist. In nearby Minnesota, the Minnesota Speleological Survey in 2000 produced a list of 82 natural caves 100 feet or more in length.
The caves fall into four categories – sandstone resulting from groundwater erosion, limestone and dolomite caves also resulting from erosion, rock shelters and crevices and volcanic caves.
The first cave that I ever visited was Cave of the Mounds near Blue Mounds in Dane County, which was on a fourth-grade field trip. Since then, my wife Sherry and I have visited caves in Iowa, Minnesota and South Dakota. We returned not long ago to the limestone and dolomite Cave of the Mounds, which at 1,692 feet is the fifth longest cave in Wisconsin and contains the oldest dated cave formations in the Midwest.
The cave was discovered Aug. 4, 1939 when limestone quarry workers blasted a section of stone and exposed an opening to the cave. But its story began some 488 million years ago during the Ordovician Period when much of North America was covered with warm, shallow seas. Calcium carbonate shells from marine life accumulated on the sea floor over millions of years, forming limestone. The limestone in the cave is galena dolomite because of its high concentration of lead ore.
The cave itself began to form more than a million years ago when rainwater from the surface started to seep through a crack. The rainwater combined with carbon dioxide formed a weak carbonic acid that is strong enough to dissolve limestone. Over time, the cave cavity developed and the water drained out. Water droplets saturated with calcium carbonate create speleothems, taking 50 to 100 years to form one cubic inch of material.
The farm where the cave was discovered was first settled in 1828 by Ebenezer Brigham, a lead miner from Massachusetts who joined the Wisconsin lead mine rush of the 1820s. Brigham set up a trading post, inn and the first post office in Dane County.
Brigham’s property went to his nephews upon his death. J.R. Brigham built the historic barn in 1883 that is still on the property, which was farmed until the 1980s. Quarrying began on the farm in 1903. After the cave was discovered in 1939, quarrying stopped. The cave opened for tours in May 1940 after walkways and lighting were installed.
Cave of the Mounds has a new visitor center but the rock and fossil shop built in 1941 still sits on top of the cave entrance. It’s part of a 100-acre park with restored prairie and savanna and rock gardens.
In 1987 the cave was designated a National Natural Landmark by the U.S. Department of Interior and the National Park Service because the many varieties of its speleothems. Among the stalactites (which grow from the ceiling) and the stalagmites (which grow from the floor) are soda straws, flowstones, curtains, lily pads, helictites and oolites or cave pearls. There also are examples of sea creatures that once lived in the ocean with fossils of cephalopods, gastropods and others. The formations come in many different colors and some of them are partially luminescent.
We toured the cave with black lights, which create an awesome experience in the dark and will certainly interest youngsters who may not appreciate geology and history.
What I appreciate about caves and what leaves a lasting experience with me is when the lights go off and you experience total darkness. You can’t even see your hand when you wave it in front of your face.
All you hear is the soft sound of dripping water as the cave formations continue their long and incredible journey of growth, one drop of water at a time.
- If you go: Cave of the Mounds is open daily from 9 a.m. to 5 p.m. Guided tours are available.