Jacksonville Esker EarthCache
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This is a road trip along a section of the Jacksonville Esker, which is located along route 191 just north of the small community of Jacksonville. For several miles you will be traveling where once water flowed under the glacier, on top of the esker.
During the most recent glacial episode in Maine the ice sheet became several thousand feet thick and covered the highest mountains in the state. Climatic warming forced the ice sheet to start receding and melting as early as 21,000 years ago. Melt water streams in tunnels within the decaying ice deposited some of the glacial sand and gravel. There are over thirty of these deposits that were left behind as ridges (eskers) when the surrounding ice disappeared. Maine's esker systems can be traced for up to 120 miles, and are among the longest in the country. C. T. Jackson (1837), who conducted the first geological survey of Maine, made an interesting remark about one such esker: "I could not help thinking, as I looked upon this natural embankment, that it would be easy for an antiquarian to mistake this ridge for a work of art, and to suppose that some of the aboriginal inhabitants of our country knew how to annihilate distance by rail roads."
The esker is one of the most striking landforms of glacial deposition. In low-lying, boggy terrain such as the Berry Bog area to the west, these snaking ridges dominate the terrain, providing vantage points and dry route ways. Eskers are usually formed of washed sand and gravel. The free-draining ridges are easily quarried, making eskers attractive targets for aggregate extraction, which is what has happened along this esker in several places. The sediments are usually horizontally- and cross-bedded sands and gravels but vary widely, a reflection of variations in flow regimes and in sediment supply. Eskers are discontinuous because sedimentation may not take place along the entire length of the sub-glacial tunnel. Blocks of the overlying ice may fall into the tunnel. Alternatively, an esker ridge may become segmented by erosion; either by melt water during deglaciation or by the action of post-glacial rivers.
This earthcache is a trip along an esker just north of Machias. Please watch carefully for traffic because the road is narrow and winding as it travels along the esker. There are several viewing areas along the trip that will allow you to look along the esker as well to both sides. In this area the esker formed a delta that was draped over the esker during a pause in the retreat of the glacier.
At the posted coordinates you will find yourself at a small roads pull off. Here you will be able to see the pine tree topped esker and the flat lands on either side of the esker. Imagine the size of this under ice river. Remember this is an earthcache and there is no physical container just an interesting earth science lesson. To log this Earthcache: You must post a photo of you and your GPS with some interesting feature/view in the background and then send an e-mail with an estimate of how high the esker is above the flat lands on either side. Remember, this is one of the largest eskers in the state. Please remember to include the name of the earthcache in your email.
If you enjoy this earthcache you may want to check the Maine Geological Survey located at (visit link)
They have developed a number of information sheets or field localities giving a great deal of information about geologic features. They also have a number of books and maps about Maine’s natural history/ geology that you might find interesting.
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