GEOLOGIC HISTORY
Around 12,000 years ago, the Wisconsin Glacier that once covered Michigan was retreating. A glacier is said to be retreating if it is melting faster than it is advancing. As it melted, whatever clay, dirt, gravel, and boulders it was carrying was deposited on the land. The accumulation of this debris makes up the moraine. There are several different types of moraines depending on how an where the debris was deposited. This EarthCache focuses on an outwash.
OUTWASH
An outwash is a deposit of sand and gravel carried by running water from the melting ice of a glacier and laid down in stratified deposits. An outwash may attain a thickness of over 300 feet at the edge of a glacier, although the thickness is usually much less; it may also extend many miles in length.
The sheet of outwash may be pitted with undrained kettles or dissected by postglacial streams. Outwash plains are commonly cross-bedded with units of alternating grain size. The ordinarily gentle slope causes the larger material to be dropped nearest the glacier, while the smaller grain sizes are spread over greater distances.
WHY HERE?
Oxford is rich in gravel pits. When the glaciers of the last Ice Age swept down over the North American landmass, they left millions of tons of gravel. The village of Oxford, Michigan (motto: “Small. Done Right”) lies atop one of these gigantic gravel veins.
LOGGING REQUIREMENTS
While standing at the posted coordinates looking north, you will be on the south edge of an active gravel quarry. There is no need to enter the quarry or even leave the trail.
In order to log this EarthCache, send me your answers to the following questions either through email from my profile page.
1. Describe the piles of debris you see in the quarry. Is it sand/gravel/rocks? What size? What color?
2. Estimate how deep and how far across the quarry is from where you're standing.
3. Pictures are not required but are appreciated. Please post a pic of you or your GPS with anything you find interesting in the area.
sources:
How a Small Town in Michigan Became the World’s Gravel Capital
GEORGE PENDLE
Outwash Geology and Hydrology
www.britanica.com
Geology of Michigan
John A Dorr Jr and Donald F Eschman