About 200 million years after this collision and the formation of Pangea, during the middle of the Mesozoic Era, the Atlantic Ocean floor started spreading. This caused a lot of stress. This caused a geologic fault. Connecticut's famous Eastern Border Fault was created. As a result, the land west of this fault was downset, creating a rift valley and causing the land to tilt an average of 15 to 25 degrees. The fault is currently inactive. The formation of this basin eventually refilled with soft fluvial and alluvial sediments.