The Lone Erratic EarthCache
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I was out caching with my dad and on the way to a cache we see this rock which he tells me it's a erratic boulder that was moved here by a glacier. I thought it was cool so I did some research on it and created a earthcache of my own.
This Erratic rock was brought down to this area by the glaciers. As the glacier moved south, it pulled along these rocks and as they moved they where ground round. They started there journey here from states up north of us and even as far away as Canada. When the glacier started melting and stopped moving south, it dropped these rocks in a erratic manner. This errtaic was dropped into this land that became a farm field. After years of plowing the erratic probably hit by the plow and then was move to the edge of the field where it sits today. And to think, this huge rock was moved here by a sheet of ice.
Here and there in Illinois are boulders lying alone or with companions in the corner of a field or someone's yard, on a courthouse lawn or a schoolyard. Many of them -- colorful and glittering granites, banded gneisses, and other intricately veined and streaked igneous and metamorphic rocks -- seem out of place in the stoneless, grassy knolls and prairies of our state. Their "erratic" occurrence is the reason for their interesting name. These exotic rocks came from Canada and the states north. The continental glaciers of the Great Ice Age scoured and scraped the land surface as they advanced, pushing up chunks of bedrock and grinding them against each other or along the ground surface as the rock-laden ice sheets pushed southward. Sometimes you can tell where the erratic originally came from by determining the kind of rock it is. A large boulder of granite, gneiss, or other igneous or metamorphic rock may have come from Canada.
When glaciers melt, they leave behind whatever they were carrying. This may consist of a mixture of rock debris and old soils, called till, material that was ground-up and deposited from the base of the glacier. Some of the most striking reminders that the landscape was once covered by glaciers are boulders and cobbles, called erratics, that dot the landscape. Unlike the rock you find in local quarries, these are exotic rocks. In Illinois, erratics are often granitic rocks like those you would find today hundreds of miles away in Canada.
Glacial meltwaters carried ground-up rock debris away from the glaciers. In the valleys of major meltwater channels, like the Mississippi and Illinois valleys, this debris settled out as layers of silt, sand, and gravel, called outwash. On dry, windy days, the finest particles of this outwash were blown across the landscape in glacial dust storms. These particles settled across the landscape to form a blanket of silt-size particles, called loess. Loess forms the basis of the young, rich soils of the northern plains of the United States.
To log this earthcache and get a smiley you must,
1. Post a picture of you next to the erratic rock with your gps in your hand.
2. Tell me how erratic rocks and boulders got to where they lie today.
3. What is the height and width of the erratic rock.
I have used sources available to me by using google search to get information for this earth cache. I am by no means a geologist. I use books, internet, and asking questions about geology just like 99.9 percent of the geocachers who create these great Earth Caches. I enjoy Earth Caches and want people to get out and see what I see everytime I go and explore this great place we live in.
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