Great Esker Park in Weymouth lies on top of an esker. An esker is formed by a stream or river in a tunnel underneath a glacier. It is made up of the sediments dropped by that stream or river. When the glacier retreats, the deposits remain, exposing a long, winding hill where the stream or river used to be. Eskers are great sources of gravel and sand (used in construction), and consequently most eskers have been stripped away for these materials.
Eskers have been desirable places to mine gravel and sand because they contain very little clay and mud. This is because the streams that deposit the materials under the glacier move very rapidly, and carry the finer-grained sediments away.
Great Esker Park is one of the few remaining places in the Boston area where you can see a relatively intact esker.
Observe the esker in the picture below. Describe the shape of the esker. Why do you think it has this shape?
An aerial picture of Great Esker Park. (Elevation is exaggerated.) From Google Earth. Approximate location of the original esker is outlined in red.
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Picture taken, along the esker, from location 2 (map on left):
Picture taken from location 3 (map on left):
