Ice! Only 16,000 years ago, Maine and New England were covered by a huge glacier which extended all the way offshore to the coastal shelf! Cape Cod and Long Island are the furthest obvious extent in the northeast; think of how a plow pushes snow at the end of your driveway.
At that time the ice over “Sabbathday Lake” and all of Maine was about one mile thick (5000’ +/-). Glaciers grow, and then they retreat. The climate warmed up and the glacier started melting (retreating). About 12,500 years ago it had receded to the northwest and the area around Sabbathday Lake was free of ice.
Most geology is recorded in 100’s of millions of years and difficult to imagine. But 12, 500 years is not very long ago.
The coast! At the time of the glacier, Maine’s ocean coastline was much futher inland in part because the weight of the ice depressed the earth’s crust.
What we now know as the coast between New Gloucester and the seacoast was about 300’ below current sea level. Nearby the ocean reached inland all the way to Sebago Lake!
The hashed blue line at the south end of the lake on the (insert) glacial map shows the approximate ice margin when the glacier paused for a while over Sabbathday.
Our esker! An esker is a sand and gravel deposit deposited in an ice tunnel by a subglacial stream. We see something like this in miniature at the end of our driveways at the end of the winter when the snow and ice melts.
The sandpits at the north end of the lake (Outlet Road) are near the end of a long esker that originates way up around Andover.
The photo (insert) is the top of our esker in the winter. Eskers are often the route of historic footpaths and roadways as they are high and dry and keep you out of the wetlands.
You will find lots of easy to understand information about our glacial history online at the Maine Geological Survey (https://www.maine.gov/dacf/mgs/explore/surficial/index.shtml)
- Sabbathday Lake Map (in the insert) with explanatory key at https://digitalmaine.com/mgs_maps/771/
- Interactive map of all Maine “surficial geology” at https://www.maine.gov/dacf/mgs/pubs/digital/surficial.htm
- Eskers made easy and interesting at https://digitalmaine.com/cgi/viewcontent.cgi?referer=https://www.google.com/&httpsredir=1&article=1490&context=mgs_publications
Written by Tom Driscoll. Previously published in the newsletter of the Sabbathday Lake Association.