Water gap

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For other uses, see Water gap (disambiguation).
Wallula Gap, seen from Wallula, Washington Main Street.
Two water gaps opened by the same river in Central Pennsylvania
View of water gaps cut by the Raystown Branch of the Juniata River through Evitts Mountain and Tussey Mountain, facing west from the summit of Kinton Knob, Wills Mountain, in Bedford County, Pennsylvania, with the town of Bedford in the foreground.

A water gap is an opening or notch which flowing water has carved through a mountain range. Water gaps often offer a practical route for road and rail transport to cross mountain ridges.


A water gap is usually an indication of a river that is older than the current topography. The river likely established its course when the landform was at a low elevation or by a rift in earths crust, with a very low stream gradient and a thick layer of unconsolidated sediment. The river therefore established its channel without regard for the deeper layers of rock. A later period of uplift caused increased erosion along the riverbed, exposing the underlying rock layers. As the uplift continued, the river, being large enough, continued to erode the rising land, cutting through ridges as they formed.

Water gaps are common in the ridge-and-valley Appalachians of eastern North America.

Alternatively, a water gap can be formed through headward erosion of two streams on opposite sides of a ridge, ultimately resulting in the capture of one stream by the other.

Notable examples[edit]

See also[edit]