Tuesday, December 27, 2016
Minna Anthony Nature Center on Wellesley Island
The islands are elongated parallel to the river, with blunt upstream ends and gentle downstream trailing slopes. Evidence of the glaciers can be seen throughout the region in the form of glacial furrows, glacial erratics, and potholes. A glacial pothole is a semi cylindrical hole gouged out of the bedrock by the scouring action of rocks and pebbles in the floodwaters of retreating glaciers. The best known (and largest) example of a pothole in the Islands is Half Moon Bay on Bostwick Island. Several smaller examples of potholes can be seen along the Eel Bay Trail portion of the Minna Anthony Nature Center on Wellesley Island. An example of a glacial furrow can be found in the road cut on Route 12 just outside of Keewaydin State Park. Here the bedrock of Precambrian gneiss has been scoured and polished by boulders at the bottom of the glaciers. Glacial erratics are boulders from elsewhere that were carried by the ice and then dumped as the glaciers melted. These can be found throughout the region.