A Gift of Geology: Artesian Wells

Elliot Witscher, guest author, was a Summer Naturalist Intern for the Cable Natural History Museum last summer. Photo by Elliot Witscher.

In May, Elliot Witscher graduated from Case Western Reserve University with a degree in Geological Sciences. As part of their experience as a Summer Naturalist Intern at the Cable Natural History Museum, Elliot participated in a Wisconsin Master Naturalist Volunteer Training. This fall, they began work at an outdoor school in Illinois.

In the bright sunlight and heat of the afternoon, the cool, fresh, flowing water from a pipe in Prentice Park in Ashland, WI, was a welcome treat. I wasn’t expecting to find a unique geological feature in an unassuming city park. But walking down the hill from the parking lot, we found a plain metal pipe, surrounded by gravel, with water gushing from it.

Standing in a circle with the 20 other people also taking the Wisconsin Master Naturalist Volunteer Training, I learned from Professor Tom Fitz that this was a flowing artesian well.

Professor Tom Fitz teaches about artesian wells in Prentice Park, Ashland, WI.
Photo by Emily Stone.

This random pipe in the middle of a city park doesn’t come from the city’s water system; it taps directly into the groundwater beneath our feet. There is no pump. Nothing brings the water up to the surface except for the pressure that it’s under naturally…with a little help from the glaciers.

That day began at a gravel pit about 30 miles to the southwest, as the crow flies, near the town of Cable, WI. At the intersection of geology and industry, our Master Naturalist class learned how the gravel pit provides various sizes of sand, pebbles, and even small boulders that are used for road fill, landscaping, and foundations.

In the gravel pit. Photo by Emily Stone.

Thousands of years ago, a glacier covered this area, and this gravel was brought here by a power river of meltwater flowing under the ice, creating a sinuous ridge of material called an esker. This is just one of many glacial landforms in the area that is built from sandy, rocky materials. [Learn more about eskers from Emily Stone during a hike on November 9. Find out more at cablemuseum.org.]

Next, Tom Fitz led us north toward Ashland, and we found ourselves traveling forward in glacial history. As the ice retreated north, water pooled up to its south, and Glacial Lake Duluth formed, covering the western half of what is now Lake Superior with much deeper water. Meltwater flowing off the glacier brought clay and other sediments into the lake.

Clay particles are very small, and can stay suspended in water for a long time, especially if wind or currents keep the water stirred up. But away from shore, where the water was calmer and winter ice cover kept out the wind for long periods, the clay settled to the bottom, creating a thick layer. All around the current shores of Lake Superior, this clay layer covered the gravel that was previously deposited by the glaciers. Iron in the clay turned the soil red.

Tom Fitz teaches the group about clay. Photo by Emily Stone. 

In the uplands of Bayfield County, inland and away from the lake, the glacial gravel is exposed to the surface. When it rains, water quickly and easily enters this permeable layer and moves downhill toward Lake Superior. In the lowlands, near the lake, the layer of clay from Glacial Lake Duluth covers the gravel. The water moving through the gravel layer becomes trapped under the impermeable layer of clay. All of the water from the uplands pushes down on the water under the clay in the lowlands, and pressure builds up.

When a well, like the one in Prentice Park, is drilled through the clay layer into the gravel layer, that pressure pushes the water up toward the surface, creating a flowing artesian well—a well that flows from confined groundwater to the surface due to pressure.

These wells are amazing sources of water, but they are limited by one major reality: if too many of them are punched through, the pressure created by the clay layer will be diminished until eventually the pressure will drop too low and the wells will stop flowing. These amazing natural phenomena are limited. If we try to develop too many, they will all be at risk.

Last summer, as I explored the backroads of Bayfield County, I found myself occasionally stumbling across little handwritten signs or Google Maps locations titled “artesian well.” I smiled to myself, thinking about the geologic marvels that led to this important resource. And then I stopped, filled my bottle, and enjoyed some clear, cold water.

For more than 50 years, the Cable Natural History Museum has served to connect you to the Northwoods. The Museum is open with our brand-new exhibit: “Anaamaagon: Under the Snow.” Our Fall Calendar is open for registration! Follow us on Facebook, Instagram, YouTube, and cablemuseum.org to see what we are up to.