Don't Fred and Wilma live in Bedrock? EarthCache
Don't Fred and Wilma live in Bedrock?
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This Eartcache is located within the Edgerton Reserve, owned by the Black Hawk County Conservation Board
With this Earthcache, I hope to give you a glimpse of the many different forces that have shaped the Iowa landscape. Over millions of years, Iowa’s surface has been smoothed by glaciers, eroded and built up by wind and water and overgrown with vegetation.
Iowa is thought of as an area of fertile farmland and rolling hills, but what lies under this area? Bedrock. How did it get there? In prehistoric times, much of what is now Iowa was covered by warm shallow seas, home to a wide variety of primitive life. Over millions of years, as these life forms died, they settled to the sea floor in layers, sometimes with impressions being left as fossils as these layers were compressed into stone.
As the climate changed and continents shifted, these ancient seafloors became dry land, exposed to the sun, wind, rain and other forces of nature. During the ice ages, this area was covered by huge moving ice sheets, hundreds of feet thick. Several different glacial advances ground the surface as they moved slowly over it, smoothing the peaks and filling the valleys. When the ice sheets melted, the material carried for hundreds or thousands of miles within the ice, known as “glacial till”, including large rocks called “glacial erratics” was left covering the surface. Melt water from these glaciers not only eroded the landscape, but also brought in additional debris known as “alluvium”.
Wind carried silt and sand (loess) was added to the mix of material covering the area allowing plants to take root. The seasonal growth and dying of the forests and prairies enriched the soil, giving Iowa its huge expanses fertile soil, much of which is now used as highly productive crop ground.
The site of this Earthcache is located in an old quarry where the accumulated material covering the bedrock was removed and limestone was mined for various purposes. Crushed stone, primarily limestone, accounts for almost 50% of Iowa’s mineral value and is used mainly in road surfaces.
To log this Earthcache, email the answers to the following questions through geocaching.com:
At the listed coordinates:
1 – Examine the exposed cross section bedrock.
a - What are the main features that run horizontally across this rock structure and how do you think these were formed?
b – Of what type of stone is this bedrock composed?
c - One of the lower layers of this exposed wall, just below knee high, contains many impressions of organisms that lived long ago. What are these impressions called and what do they tell you about this layer?
d – If possible, post a picture of you or your team in front of this structure.
At the parking coordinates:
2 – You will find the parking area is bordered by a number of large stones. Most of these are of stone similar to that found in the quarry, however, one is noticeably different.
a – What is this type of rock called?
b – How does this rock differ from the others and bedrock found in the quarry?
(For example: Is it harder or softer? What is it made of? Are any fossils found in this rock?)
c – How did the side of this rock get ground flat (note the striations on this surface)?
Additional Hints
(No hints available.)
Treasures
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