Brief outline of Pennsylvania’s Geologic History
Kurt Friehauf
435-405 million years ago – Silurian passive margin
Once the colliding volcanic island arc was stopped dead in its tracks, the Taconic Mountains began to erode. The sediments washed off of the mountains and deposited on the land to the west and in the ocean to the east. The new sediments (shown here in green) lie directly on top of the eroded, folded, older sediments creating the angular unconformity.
