One of the most well-known faults in Connecticut is the Eastern Border Fault which starts south of New Haven (the exact origin is under water) and extends 130 miles north to Keene, New Hampshire.
The Eastern Border Fault is associated with the Connecticut Valley. Pangaea began to split, forming the present Atlantic Ocean. Besides the big split of the Atlantic, many smaller faults cracked the land due to the stretching stresses. These "rift valleys," similar to today's Death Valley, one of these rift valleys is known as the Eastern Border Fault.