Metamorphic rocks can be found in the Eastern and Western Uplands of Connecticut. The Eastern Uplands are a group of hills, very closely packed together. One site where metamorphic rocks can be located is the Bolton Ridge, running from the Massachusetts border south to Portland. Another site is on Route 95 as it goes up into New York. Here shiny, scaly rocks can be seen on the left. Other metamorphic sites include Bald Mountain, Soapstone Mountain, Tolland Range, Woodstock, Drumlin Field, and the Willimantic Basin. Along the Rhode Island border and swinging around parallel to Connecticut’s Coast is another range of ridgy terrain. The ridges of this range run north-south along the Rhode Island line to the town of north Stonington, and from there swing east-west to Joshua Rock on the Connecticut River in Lyme. This range is referred to as the Mohegan Range. The Western Uplands include several plateaus, the highest of which is the Taconic Plateau in the very northwest corner of the state where Connecticut, Massachusetts and New York meet. The most extensive and best-known plateau is the Litchfield Hills Plateau. It is the extension of the Berkshire Mountains in to Connecticut.
Sedimentary rock can be seen in the brownstone of the Central Valley. This reddish rock fills most of the valley and is the product of the erosion of ancient mountains. The thick deposits of recent glacial sediments from the ice age are not only favorable for agricultural development but are also most suitable to supporting residential, commercial and industrial development. Most of the soils that formed from the glacial deposits are well-drained, which means that waters from heavy rain flow freely and sewage systems are not likely to fail. Lake Saltonstall, east of New Haven and the Farmington River Valley is a site of sedimentary rock.
The Central Valley is also home to igneous rock called basalt and gabbro which can be found in the high ranges known as traprock ridges. The Great Wall of the Central Valley is the Metacomet Ridge, a nearly continuous ridge of rock that runs from Branford, Connecticut to Northampton, Massachusetts. The Ridge lies entirely in the Central Valley and is known by several local names along its north-south route. In Connecticut, it is called Saltonstall Ridge, Totoket Mountain, Beseck Mountain, Higby Mountain, Lamentation Mountain, The Hanging Hills, Avon Mountain, Talcott Mountain, Penwood Mountain, and West Suffield Mountain. Traprock that formed underground can be seen in New Haven’s East and West Rock as well as in Hamden’s Sleeping Giant.