As you descent Still River Depot Road toward the Oxbow National Wildlife Refuge you will see a broad valley.  Ten thousand years ago, this valley was covered by over a mile of ice.  This moving, frozen river carved the valley as we know it today.  When glaciers advance, they push great amounts of debris before them.  These are known as moraines.  As the glacial age ended, the ice began to melt.  Moraines acted as dams.  Meltwater accumulated behind them creating huge lakes.  In this instance ancient Glacier Lake Nashua, extending from Boylston, Massachusetts, to Nashua, New Hampshire, came to be.  During various stages Glacial Lake Nashua ranged from 27 to 135 meters in depth. Deltas were formed at lake margins depositing up to 50 meters of sand and gravel.  The photograph below, taken during the construction of Wachusett Reservoir, is of an exposed delta. Silt and clay, in some places as deep as 10 meters, was deposited in lake bottoms. Eventually breaks in the moraines exposed the valley as it is today. In the late 1800s several brick-making operations in the area relied on the clays as their raw materials. Large sand and gravel deposit removal continues to this day.

Glacial Lake



Glacial Lake Nashua. Foreset and bottomset beds of the sand plain of the Clinton stage, looking southwest at a point on the west side of the submerged Nashua Valley three miles southwest of Clinton, Mass. Superfine sand at the water level (367 A.T.), coarser above. Short slope at left rises to the 405- foot terrace. Marlboro quadrangle. Worcester County, Massachusetts. October 23, 1906.

 

 

 

Eskers

During the last ice age, some 12,000 years ago here in our area, the land was covered with slowly moving rivers of ice, about a mile thick. As these glaciers thawed, streams and rivers formed on and in the glacier itself. These streams and rivers meander, depositing beds of rocks, gravel and sand.  After the glaciers melted, the stream beds remained where originally deposited, leaving long, winding, steep sided ridges, eskers. As you approach the Esker Trail at the Oxbow National Wildlife Refuge you will be confronted with a steep hill, the side of the esker. Walking along the top, the ridge becomes narrower. Even with forest cover, you can see its steep-sided slopes.

You can get a better view of what the esker may have looked like before post-glacial vegetation took hold in New England. This photo of an esker was taken as vegetation was removed when Wachusett Reservation was built.

Glacial Lake2



Glacial Lake Nashua. Esker (partially submerged) formed at the Boylston stage tributary to the delta-sand plain terrace at 470 +/- feet, three miles south of Clinton, Mass., east side of valley. In the background, delta sand plains of the Clinton stage. Marlboro quadrangle. Worcester County, Massachusetts. August 24, 1906.