Ralph Lewis's Geology of Connecticut Landscapes

This series of slides illustrates how glaciers affected the landscape of Connecticut.

Click on the image for a larger view

Glaciers had an important influence on our land surface. As great sheets of ice moved over our hills, they exploited the N-S valleys and carved away rocks that were weak and fractured.

This map shows the extent of the glaciers about 20,000 years ago. Most of Canada and Greenland were covered, as well as New England.

Here is a map of the ice in our region. The continental glacier covered Mt. Washington in New Hampshire (6018 feet). This ice sheet entered Connecticut about 26,000 years ago, reached its maximum about 21,000 years ago, and was melted out of the state by 15,500 years ago.

The glaciers also covered the state earlier during the Ice Age, about 150,000 years ago, and many people think that they completely changed the topography. In fact, the ice modified features already present.

As the ice moved southward, it deepened valleys and rounded hills. The pre-existing N-S grain of the land was preserved and accentuated.

This mechanism is evident in modern glaciers, such as this one in Alaska where the rock surface (right side) is being rounded.

As the ice rounds off the hills, it picks up the broken rock fragments and other sediments.

Here is some recently-eroded rock material in Alaska.

In Connecticut, this sedimentary rock in the central lowland shows how harder sections were rounded while less-resistant rock was gouged out. This happened at small scales like this as well as in major valleys.

Glacial plucking on the south sides of hills also influenced the shaped of the land, and provided rock shelters for paleo-North Americans.

This topographic map shows a glacially-plucked hill in Deep River. The contour lines are closer together on the south side of the hill, showing a steeper slope.

The ice moved toward the viewer over this hill. You can see how the plucked hillside could become an overhang and shelter for a weary traveler.

Next page: Ct. glaciers continued (to be added)

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	Glaciers had an important influence on our land surface. As great sheets of ice moved over our hills, they exploited the N-S valleys and carved away rocks that were weak and fractured.
	This map shows the extent of the glaciers about 20,000 years ago. Most of Canada and Greenland were covered, as well as New England.
	Here is a map of the ice in our region. The continental glacier covered Mt. Washington in New Hampshire (6018 feet). This ice sheet entered Connecticut about 26,000 years ago, reached its maximum about 21,000 years ago, and was melted out of the state by 15,500 years ago.
	The glaciers also covered the state earlier during the Ice Age, about 150,000 years ago, and many people think that they completely changed the topography. In fact, the ice modified features already present.
	As the ice moved southward, it deepened valleys and rounded hills. The pre-existing N-S grain of the land was preserved and accentuated.
	This mechanism is evident in modern glaciers, such as this one in Alaska where the rock surface (right side) is being rounded.
	As the ice rounds off the hills, it picks up the broken rock fragments and other sediments.
	Here is some recently-eroded rock material in Alaska.
	In Connecticut, this sedimentary rock in the central lowland shows how harder sections were rounded while less-resistant rock was gouged out. This happened at small scales like this as well as in major valleys.
	Glacial plucking on the south sides of hills also influenced the shaped of the land, and provided rock shelters for paleo-North Americans.
	This topographic map shows a glacially-plucked hill in Deep River. The contour lines are closer together on the south side of the hill, showing a steeper slope.
	The ice moved toward the viewer over this hill. You can see how the plucked hillside could become an overhang and shelter for a weary traveler.
	Next page: Ct. glaciers continued (to be added)
	Close this window to return to the main menu page