One cannot ignore the geologic forces that were at work to produce the landforms which now exist in Connecticut. It is as important to present this section as a beginning of the history of Connecticut as it is to teach our students about the first settlers of Connecticut. “What was here before the Indians?” is a question many sixth grade students ask, and so this unit begins with the last ice Age.
Connecticut is currently a place of gently sloping hills and valleys, but this has not always been the case. Many thousands of years ago, Connecticut was a place of very steep mountains which rose many thousands of feet. The rains were the major force which began to erode the rock and soil of these mountains. Fast-moving water flowed to the lowlands carrying with it eroded sand and rock. This material was deposited in thick layers in low-lying areas. A great crack in the land, called a fault, developed in a north-to-south configuration across the state. Consequently, a huge block of rock dropped down to form the beginning of the great Connecticut Valley.
As the years passed, the rains continued to wash rock and sand down from the higher lands to the valley. Lava flowed to the surface through the cracks in the original fault and through many newly formed cracks in the earth’s surface. Today one can find many layers of sand, gravel, and clay intermixed with layers of cooled lava, called traprock.
The next tectonic force to change the shape of Connecticut’s landforms was the enormous pressure that was building up on both sides of the valley. This force was squeezing the material into the valley from both sides. But the rock in the valley was very hard rock; it wouldn’t crumble under the pressure of this enormous force. Instead, the rock broke in several places, causing one piece to slide over another. Gradually, the erosive power of running water wore away the softer material that was in the valley, leaving behind the harder shale and traprock. After thousands of years of erosion, the traprock and other hard rock that had become exposed formed a series of long hills. In the New Haven area, two of these hills are called East Rock and West Rock.
The remainder of the state is made up of granite, a very old and hard type of rock. As the rivers and streams wore away these areas, steep slopes and valleys were produced, contrasting with the gentle slopes of the central valley. One can easily view these differences by comparing the valley of the upper Housatonic River with the Connecticut Valley. Another type of rock exists in Connecticut that is made up of limy materials that were deposited in the ocean which once covered this area. This deposit lies in the Western section of the state from Danbury to Massachusetts.
The last major event in the geologic history of Connecticut was the ice age. Many thousands of years ago the climate began to get colder and the winters became more severe and longer than normal. Eventually the temperature did not rise enough to allow the snow to melt. The snow piled up higher and higher. The lower levels of this snow began to turn to ice under the enormous pressure. In the southern areas of Connecticut, the thickness of the glacier was believed to have been around 1,000 feet; but in the northern areas, it is believed to have been as much as two miles. As stated before, the lower levels were under enormous pressure from the weight of all that snow and ice. The ice on the bottom squeezed out from underneath and caused the glacier to move. The ice moved slowly southward over the hills and valleys; all of Connecticut was covered, and the edge of the ice reached as far south as Long Island. The ice pushed rock and other material ahead of it. In some instances, rocks as large as houses were frozen into the bottom of the glacier. The glacier acted like coarse sandpaper, smoothing down the rock over which it passed.
Approximately ten thousand years ago, the glacier began to melt. As it melted, it deposited much rock, sand, and clay all over Connecticut. One can see many enormous boulders throughout the state. One such boulder can be found in the woods at the West Rock Nature Center. These huge boulders are called “erratics.” They are the rocks that were carried along by the glacier. Although they appear tremendous in size to us, they were mere “pebbles” in comparison to the glacier.
When all of the ice and snow melted away, Connecticut’s surface was devoid of any kind of life. The state had been stripped of its plant and animal life by the cold climate which had prevailed for thousands of years. Eventually, seeds found their way to the area. By wind, water, and animals, seeds from neighboring regions that were not affected by the ice were deposited over the state. In a few thousand years, Connecticut came back to life.
The present landforms of Connecticut are a result of the aforementioned forces that had been at work. Connecticut has four regions in the western and eastern sections of the state. Bear Mountain, in the northwest section, is the highest point in Connecticut at 2,315 feet. Burley Hill, in the northeastern section, is the second highest point at 1,315 feet. The state is approximately 100 miles east to west, and approximately 50 miles north to south, covering approximately 5,000 square miles of area.
(See figures 1-5 for further information on above.)