Hello there! I have created this earthcache to teach you about the unique geology of Jo Daviess county in Illinois, and why it is more hilly then the rest of Illinois.
What is unique about the geology of Jo Daviess County?
Unlike 85% of Illinois that was covered in a glacier during the Pleistocene Epoch period (1.6 million to 10,000 years ago) Jo Daviess county was untouched by the glaciers that drifted. The great glaciers, with ice up to 2 miles thick, acted like bulldozers on much of the Midwest, flattening out the landscape as they crept down from the north. However, This intact area that the glaciers missed is among a unique landscape that includes parts of Wisconsin, Minnesota, and Iowa, known to scientists as the driftless area. As a result of the great glaciers missing the drift less area, the scenery you see today is very unique and a marvel to many geologists. Since the driftless area wasn't touched by the glaciers, it remained hilly and rugged with rock formations, as much of the Midwest may have looked before the glaciers. The oldest rock formations, made up of limestone, are roughly 450 million years old and can be seen along the Apple River, the Galena River, and the quarry west of Elizabeth, IL. The youngest rocks are just over 450 million years old, made of dolomite, which is a very hard rock that repels the forces of erosion. These rocks lie beneath the highest points in the state, like Horseshoe mound. At one time, these mounds erre mere bumps in the landscape, but survived the millions of years worth of weather and drastically changing landscape.
How has the landscape changed?
As the glaciers moved downward, they created a snowplow like condition of depositing soil and slit into the driftless area. Over the millions of years, erosion has made a significant change to the geological landscape of this area. Water that was melting from the glaciers also formed paths and cough through making valleys and developing pathways to what is now the Mississippi River. Tectonic activity, or movement of the earth's plates, also caused streams to begin cutting downweard. All this motion produced jagged rock formations and the landscape you see today.
What is the cause of the driftless area?
The earths rotating tilt and periodic distancing away from the sun ocassinaly coincided to cool the climate. Snow and ice from the north thickened and crept southward through Canada and then the upper Midwest. Geologists aren't certian why glaciers bypassed the driftless area, but some speculate that a hard plain of bedrock granite in northern Wisconsin, perhaps the site of an old, worn down mountain range, divertido the ice or slowed it down so it stopped short of the driftless area during each glacial period, much like water diverts around a solid piece of rock in a shallow stream.
In order to log this EarthCache as found, you will need to complete the following.
1. Stand near GZ and look South. Observe the mound you are looking at and describe the shape of it.
2. How do you think the mounds have been shaped over time?
3. Compare these mounds to other mounds and mountains you have seen before? How are they similar/different?
4. Please take a picture with a personal item or of yourself to prove you have visited this location
All of these answers can be messaged to me. I hope you have a great day, and keep on caching!