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Welcome to the next edition of Doc.’s Roadside Geology Tour. Today’s tour takes us to a quiet little wide spot in the road…..Just south of the border.
Clear Lake, IA…. A quiet little resort town known for it’s tiki bars, ballrooms and secret fishing holes.
This town has not only ushered through Presidential hopefuls, it was an unwilling witness to The Day the Music Died, and just a few centuries before, was right in the middle of the path of a glacier bound for Des Moines. Talk about being the wrong place at the wrong times…!
The listed coordinates will bring you to a wide spot in the road which is home to an informational kiosk of a Wind Farm established in the heart of prime Iowan croplands.
“But WHY are they HERE???”
Good question! It’s because this place is “SPECIAL!”
This special place is very near the Eastern border of the path of the Des Moines Lobe. The landscape you see and the dirt you are standing upon was desposited about 12,000 years ago. As you travel due east approximately 5 miles, the landscape you see before was not in the path of the Des Moines Lobe. That landscape (erratics, dirt, et al), is classified as the Iowan Surface, displays the ongoing erosive changes on glacial deposits from 500,000 years ago.
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Iowa is truly a testament of diverse landscapes formed by eons of climatic changes. It's deep limestone base depicts it's history as the floor of a great inland sea 375 million years ago. As the sea advanced and retreated, other lifeforms developed and flourished.
Around 500,000 years ago, global warming took a hiatus and this region of the world was plunged deep into an Ice Age. As the great ice sheets receded, deep deposits of glacial debris buried the landscape. Over the centuries, the glacial deposits were eroded by wind and water to create steeply rolling hills and valleys.
As global warming continued, the rich landscape again began to flourish with new adaptive forms of flora and fauna. Life was good until someone threw the switch about 16,000 years ago and the region was once again plunged in the midst of another Ice Age.
The last glacier to enter Iowa advanced in a series of surges beginning just 15,000 years ago and reached its southern limit, the site of modern-day Des Moines, 14,000 years ago. The landscape was once again re-sculpted. Glacial outwash fields and deep deposits of silt, sand, pebbles, boulders, clay and peat created the new landscape which lays before you. The freshly glaciated landscape developed into rich grassland prairies as global warming once again established a hold.
This subtle terrain also was ideally suited for agriculture. As settlers established a foothold in the region, the rich landscape was once again transformed from lush fields of wild grasses to orderly rows of corn, wheat and beans.
The gentle, undulating contours of this massive expanse of prairie also provide a perfect environment for an additional crop to be harvested ~ That solar entity called Wind.
Wind is air in motion. The sun helps cause wind. The sun heats up the earth, although it heats up the land and water at different rates. The air above the land heats up quite a bit faster. The hot air flows up into the sky and begins to cool. The cooler air begins to flow out over the water. The cooler air begins to settle downward exerting pressure on the air. This pressure creates wind.
Near the surface of the Earth, friction from the ground slows the wind down. During the day, when convective mixing is stirring up the lower atmosphere, this effect is minimized. At night, however, when convective mixing has stopped, the surface wind can slow considerably, or even stop altogether.
Wind maps help in selecting a site, but the actual terrain has a lot to do with it. Ideally the location would be free from trees and buildings in all directions and much higher than the surrounding area. Placing a wind farm in a valley surrounded by trees and hills would not be a good choice. As a guideline, plains areas are the best for wind farm with roughly 93% of the area being exposed to the wind. Plains with a gently rolling terrain will produce a more consistent wind due to smaller temperature fluctuations and a more consistent friction quotient. Conversely, mountain summits have a rating of 3% being exposed to highly variable winds.
This particular site was specifically chosen for it’s terrain and quality of ongoing wind production. It was also chosen so you could learn a little more about this special part of Iowa's Geology.
To log this EarthCache, please forward in an e-mail the following:
1. What is your elevation reading at this site?
2. Please describe the type and colour of soil you are seeing at the edge of the fields. (Sandy, silty, loamy, etc.)
3. Please take a handful of the soil and add a little water. Can you shape it or not?
…and….
4. Please post a picture documenting your experience here.
Thanks for joining me on this edition of Doc.'s Roadside Geology Tour ~ South of the Border!
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