For the most part the rivers follow open valleys along belts of weak strata; but they frequently pass through sharp-cut notches in the na1row ridges of the stratified beltthe Delaware water-gap is one of the deepest of these notches; and in the harder rocks of the crystalline belt they have eroded steep-walled gorges, of which the finest is that of the Hudson, because of the greater height and breadth of the crystalline highlands there than at points where the other rivers cross it.
Their crest lines are often of nearly uniform height for miles and generally are little broken except by an occasional V-shaped wind gap, a narrow water gap or a rounded knob.
The mountain has a north-east-south-west trend, crossing the Delaware river at the Delaware Water Gap and continuing S.W.
At the Water Gap the ridge is cut through to its base, and the Delaware river flows through the opening.
The mountains make up 2400 square miles that overlooks the Delaware Water Gap and borders Lake Wallenpaupack.