The Delaware Water Gap is on the border of New Jersey and Pennsylvania where the Delaware River cuts through a large ridge of the Appalachian Mountains. A water gap is a geological feature where a river cuts through a mountain ridge. The Delaware Water Gap is the site of the Delaware Water Gap National Recreation Area, which is used primarily for recreational purposes, such as rafting, canoeing, swimming, fishing, hiking and rock climbing. With a fishing license, one can fish in the Delaware for carp, shad and other fish. The Delaware Water Gap began to form 450 million years ago when quartz pebbles were deposited in a shallow sea, on top of the Ordovician Martinsburg shale. The Martinsburg Shale was uplifted when a chain of volcanic islands collided with North America around the same time. These islands went over the North American plate, and deposited rock on top of plate, forming the Highlands and Kittatinny Valley.
Contributions by Oksana the russian, 18.104.22.168, and WallyFromColumbia.