water gap

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Two water gaps open 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 roads and railroads to cross a mountain ridge.

A mountain pass is similar in appearance to a water gap, but without a watercourse flowing through it.^{[citation needed]}

Geological implications

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, 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 river-bed, exposing the underlying rock layers. As the uplift continued, if the river is large enough, it will continue to erode the rising land, cutting through ridges as they form.

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.

Prominent water gaps

• Columbia Gorge, Oregon and Washington, United States
• Delaware Water Gap, United States
• Manawatu Gorge, New Zealand
• Potomac Water Gap, United States
• River Susquehanna (Central Pennsylvania): (40°35′05″N 76°59′32″W / 40.5847°N 76.9921875°W / 40.5847; -76.9921875^[1])
• Heavitree Gap, Alice Springs, Australia
• Numerous water gaps cutting through the North Downs and South Downs escarpments in southern England, including those of the Mole (at Dorking) and the Great Stour (from Ashford to Sandwich via Canterbury).

See also

• Peneplain
• Wind gap (geographical feature)

References