Glacial Pothole

July 26, 2005


Provided by: Heather Renyck, Milford High School, NH
Summary authors & editors: Heather Renyck

The above photo showing a glacial pothole was taken near Shelburne Falls, Massachusetts on May 31, 2005. This was but one of many such cavities, which ranged in size from a few inches to 39 feet (12 m) in diameter, at the base of Salmon Falls. Melting glaciers at the end of the last ice age produced huge discharges in those rivers draining the ice sheets. As a result of the powerful flow, stones trapped in cracks of the riverbed bored their way to the bottom by gyration and vibration. The rocks of Shelburne Falls are believed to be part of a volcanic arc that collided with the ancient Laurentia land mass during the Taconic orogeny (485 to 470 million years ago).

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