Fen, kame, esker — what do these glacial landmark words mean?

Photo of kids walking on an exhibit

Walking along the glacial landmark tour inside the entrance of the Dickinson County Nature Center, visitors can to experience replicas of many of the places created by the Des Moines Lobe of the Wisconsin Glacier when it was in the county about 12,000 years ago.

From bouncing on a fen to climbing a miniature kame to walking on an esker balance beam — all of the these land features can actually be seen in Dickinson County.

But these are some weird names. A fen? A kame? An esker? What in the world are those?

Glad you asked.

Fen

A fen is a peat-forming wetland that receives nutrients from sources other than precipitation — other than from rain, snow, etc. They are fed from groundwater, not surface water, so it makes them ideal habitat for plants and animals. The Spirit Lake Fen has four rare orchid species as well as grass of parnassus.

Walking on the peat makes a fen feel almost bouncy.

Photo of kids bouncing on a fen

Fens have a special feature called a flark, which are hollows that fill with water. In these flarks live several species of small snails.

Fens are fragile and rare, most having been harmed by mining or agriculture. When at a fen, make sure to protect it from harm.

In northwest Iowa, you can see this landform in person at the Silver Lake Fen, 1452 110th Ave., Lake Park.

Kame

Kames are hills or mounds made of sand, gravel and glacial till — otherwise known as dirt — that accumulate in a low spot on a glacier that is melting and retreating. When the glacier melts, all the sediment on top of it lands of the surface of the ground and creates a hill-like mound.

Kames can be easy to identify because of what they are made of. They are generally sandy and rocky instead of being made up of the main soil type of the land on which it sits. They are also usually just one mound on flat ground instead of part of rolling hills.

In northwest Iowa, you can see this landform in person in Kenue Park, 2279 170th St., Okoboji, or at the Ocheyedan Mound, 170th St., Ocheyedan.

Kettlehole

A kettle — otherwise known as a kettlehole or prairie pothole — was created when a left-behind chunk of glacial ice melted slowly after the main glacial sheet was gone. This created a bowl shape in the land that doesn’t have anywhere to drain, so water levels change with rain and snow.

Because kettleholes have areas that are dry near the top to marshy at the bottom, hundreds of species of plants can all live in one small areas. They are often the home to endangered wildlife as well.

In northwest Iowa, you can see this landform in person at the Freda Haffner Preserve at 1838 210th St., Milford.

Esker

An esker is a long, winding ridge. It was created when a glacier left behind water and sediment as it retreated. Streams that flowed through tunnels in an below the ice left the sediment behind in long ridges, like upside down river beds. Eskers range from 16 to 1,600 feet high and 160-1,600 feet wide. They can be hundreds of feet long up to 10 miles and are located where the original glacial river was.

Photo of a child walking on an esker

Eskers are usually made of sand or gravelly drift.

In northwest Iowa, you can see this landform in person at Kettleson Hogsback, one miles west of Highway 276 on 125th Street in Spirit Lake.

(Read about the landform regions that make up the state of Iowa.)

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