Michael Conte, Jr.
There have been several glaciations that have had an impact on Connecticut geology with the last glacial activity ending about 10,000 years ago. In order to have a glacier, certain conditions must exist such as low temperatures, which do not allow all of the snow to melt (permanent snow line), heavy snowfall and mountains that allow a build-up.
The last glacier spread from Canada to the middle of Long Island Sound and the trapped gravel and rock helped to smooth out areas as well as leave deep tracks in the surface. (The rocks used to mark the surface were “plucked” from outcrops or just dropped on the ice from mountain ridges.) As the ice receded, sand and clay deposits were left in various areas around the state which led to the development of certain industries using these deposits. (sand for quarries, clay for bricks)
Glacial activity tends to modify existing landforms. The Connecticut Valley has a rich deposit of alluvial soil that provides the region with an excellent agricultural system. This valley was a exception to the general soil left in New England because most of the valley was an old lake bottom. More in line with the rest of New England, Connecticut has been left with glacial till (a mixture of sand, clay and rocks) which make farming unprofitable. In this manner many decisions about our industry and commerce were made thousands of years ago.
An example of the force glaciers have can be seen all around us by finding large rocks called “erratics“ which are seemingly out of proportion and design with the surrounding formations. These rocks were carried a great distance in the glacial ice and then deposited on the ground. (An example would be in the Western Highlands on Fountain Street where you can find traprock on paths in the woods.)
Other effects of glaciation that one might investigate are its effect on sea level, outwash structures, kettleholes, moraines, till, and ice contact drifts to mention a few. (The use of a surficial geology map would be a great help in presenting this material—see lesson plans.)