Our Ocean: How It Works
Tony Vuolo
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How The Connecticut Coast Is Formed
The geologic history of the past 20,000 years tells us why the coast looks as it does. The two building blocks of the coast are
bedrock
and
drift.
The bedrock is the foundation, is found beneath the unconsolidated sand and soil. The bedrock one sees at the coastline is the earth’s outer layer or crust. The two most common types of bedrock along the Connecticut coast are gneiss (pronounced “nice”) and granite. Both of these are extremely hard and resist erosion. Drift is simply just sediment. It is made up of gravel, sand, silt, and clay that glaciers deposited over Connecticut. Drift is formed as glaciers chisel through the landscape grinding up rocks. One main type of drift is
till,
large angular boulders surrounded by sand, silt, or clay. The other main type is
stratified drift
, layered sand and gravel. Islands are also made up of these materials, but can differ. For example, both the Thimble Islands and coast of Branford are made of bedrock, while the coast and islands at Norwalk are stratified drift, sand and gravel. The Connecticut coastline was not only formed by the scouring and deposition of glaciers, but storms have caused continued shaping from erosion. These storms formed many large and powerful waves, which beat against the shore giving it its shape.