This earthcache was set up for SEMAG Meet & Greet #100 - The Centennial Event (GCA56E4). Special thanks to groopsoop for the help with the earthcache description!
An esker, also called eskar or eschar, is a long, narrow, winding ridge composed of stratified sand and gravel deposited by a subglacial or a glacial meltwater stream. Eskers may occur unbroken (often serpent-shaped) or in detached segments. They are only found in areas that were once glaciated.
In North America most eskers are located south of 72º N, suggesting that eskers require a wet-based glacier for their formation. Because they were created by glacial meltwater they tend to meander across the surface and may resemble the drainage patterns of rivers and streams of today.
Eskers may range from 16 to 160 feet (5 to 50 m) in height, from 50 to 1,600 feet (500 m) in width, and a few hundred feet to tens of miles in length. The highest Esker in the United States is located in Weymouth MA in Great Esker Park. At its highest point it measures 90 feet.
There are three commonly held views on where esker deposits form within a glacier:
1. in englacial or subglacial channels in the form of tunnels. If the tunnel is englacial,
then it is possible that sediment was lowered to the surface upon melting,
2. in ice-walled trenches at the base or surface of the glacier, or
3. at the end of the glacier as fans or, if the ice margin is underwater, as deltas.
Eskers tended to form when the glacier was slow and sluggish. After the retaining ice walls melted away, stream deposits remained as the characteristic long winding ridges.
For this earthcache it’s important to know the distinction between eskers and moraines since there may be some similarities and both can be found in the surrounding area. As mentioned above, eskers are narrow and comprised of stratified sand and gravel. It is unusual to find large boulders on an esker. Moraines, on the other hand, often have a bull-dozed appearance of soil and rock ranging in size from silt-sized glacial flour to huge boulders. Moraines are not melt-water depositions but are debris carried with the glacier and left behind as the glacier retreated.
Logging Requirements:
1) Note the composition of the ground of this Esker. What about the ground's composition supports the fact that this is an esker and not a moraine? What other characteristics do you observe of this formation that supports the fact that it's an esker and not a moraine?
2) Estimate the height of this esker at its heighest point.
3) Please upload a photo of you or a geocaching item at or near GZ as a proof of visit.