Water gap

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Wallula Gap, seen from Main Street in Wallula, Washington View from Wallula Main Street IMG 1480.JPG
Wallula Gap, seen from Main Street in Wallula, Washington
Two water gaps opened by the same river in central Pennsylvania, foreground and background, separated by settlements in flat lands Relieve apalachano.jpg
Two water gaps opened by the same river in central Pennsylvania, foreground and background, separated by settlements in flat lands
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 Bedford-gaps.jpg
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 a gap that flowing water has carved through a mountain range or mountain ridge and that still carries water today. Such gaps that no longer carry water currents are called wind gaps. Water gaps and wind gaps often offer a practical route for road and rail transport to cross the mountain barrier.

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Geology

A water gap is usually an indication of a river that is older than the current topography. The likely occurrence is that a river established its course when the landform was at a low elevation, or by a rift in a portion of the crust of the earth having a very low stream gradient and a thick layer of unconsolidated sediment.

In a hypothetical example, a river would have established its channel without regard for the deeper layers of rock. A later period of uplift would cause increased erosion along the riverbed, exposing the underlying rock layers. As the uplift continued, the river, being large enough, would continue 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 may 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

See also

Related Research Articles

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Canyon Deep ravine between cliffs

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Geology of the Appalachians

The geology of the Appalachians dates back to more than 480 million years ago. A look at rocks exposed in today's Appalachian Mountains reveals elongate belts of folded and thrust faulted marine sedimentary rocks, volcanic rocks and slivers of ancient ocean floor – strong evidence that these rocks were deformed during plate collision. The birth of the Appalachian ranges marks the first of several mountain building plate collisions that culminated in the construction of the supercontinent Pangaea with the Appalachians and neighboring Little Atlas near the center. These mountain ranges likely once reached elevations similar to those of the Alps and the Rocky Mountains before they were eroded.

Intermontane Plateaus physiographic division of the United States

The Intermontane Plateaus of the Western United States is one of eight U.S. Physiographic regions (divisions) of the physical geography of the contiguous United States. The region is composed of intermontane plateaus and mountain ranges. It is subdivided into physiographic provinces, which are each subdivided into physiographic sections.

Delaware Water Gap Geological feature along the Delaware River

The Delaware Water Gap is a water gap on the border of the U.S. states of New Jersey and Pennsylvania where the Delaware River cuts through a large ridge of the Appalachian Mountains. The gap constitutes the southern portion 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.

Geology of the United States Regional geology

The richly textured landscape of the United States is a product of the dueling forces of plate tectonics, weathering and erosion. Over the 4.5 billion-year history of our Earth, tectonic upheavals and colliding plates have raised great mountain ranges while the forces of erosion and weathering worked to tear them down. Even after many millions of years, records of Earth's great upheavals remain imprinted as textural variations and surface patterns that define distinctive landscapes or provinces.

Ridge-and-Valley Appalachians Physiographic province of the larger Appalachian division

The Ridge-and-Valley Appalachians, also called the Ridge and Valley Province or the Valley and Ridge Appalachians, are a physiographic province of the larger Appalachian division and are also a belt within the Appalachian Mountains extending from southeastern New York through northwestern New Jersey, westward into Pennsylvania and southward into Maryland, West Virginia, Virginia, Kentucky, Tennessee, Georgia and Alabama. They form a broad arc between the Blue Ridge Mountains and the Appalachian Plateau physiographic province. They are characterized by long, even ridges, with long, continuous valleys in between.

Geology of the Death Valley area

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Gap (landform) landform that is a low point or opening between hills or mountains or in a ridge

A gap is a land form that is a low point or opening between hills or mountains or in a ridge or mountain range. It may be called a col, notch, pass, saddle, water gap, or wind gap, and geomorphologically are most often carved by water erosion from a freshet, stream or a river. Gaps created by freshets are often, if not normally, devoid of water through much of the year, their streams being dependent upon the meltwaters of a snow pack. Gaps sourced by small springs will generally have a small stream excepting perhaps during the most arid parts of the year.

Dakota Hogback

The Dakota Hogback is a long hogback ridge at the eastern fringe of the Rocky Mountains that extends north-south from southern Wyoming through Colorado and into northern New Mexico in the United States. The ridge is prominently visible as the first line of foothills along the edge of the Great Plains. It is generally faulted along its western side, and varies in height, with gaps in numerous locations where rivers exit the mountains. The ridge takes its name from the Dakota Formation, a sandstone formation that underlies the ridge. The hogback was formed during the Laramide orogeny, approximately 50 million years ago, when the modern Rockies were created. The general uplift to the west created long faulting in the North American Plate, resulting in the creation of the hogback.

Stream capture geomorphological phenomenon

Stream capture, river capture, river piracy or stream piracy is a geomorphological phenomenon occurring when a stream or river drainage system or watershed is diverted from its own bed, and flows instead down the bed of a neighbouring stream. This can happen for several reasons, including:

Wills Mountain mountain in United States of America

Wills Mountain is a quartzite-capped ridge in the Ridge and Valley physiographic province of the Appalachian Mountains in Pennsylvania and Maryland, United States, extending from near Bedford, Pennsylvania, to near Cumberland, Maryland. It is the northernmost of several mountain ridges included within the Wills Mountain Anticline.

Tussey Mountain mountain in United States of America

Tussey Mountain is a stratigraphic ridge in central Pennsylvania, United States, trending east of the Bald Eagle, Brush, Dunning and Evitts Mountain ridges. Its southern foot just crosses the Mason–Dixon line near Flintstone, Maryland, running north 130 km (80 mi) to the Seven Mountains of central Pennsylvania, near Tusseyville, making it one of the longest named ridges in this section of the Ridge-and-valley Appalachians. The ridge line separates Morrison Cove from the Woodcock Valley and Friends Cove from the Black Valley. Tussey Mountain lies in, and the ridge line forms parts of the borders of, Centre, Blair, Bedford and Huntingdon counties.

Geology of Pennsylvania

The Geology of Pennsylvania consists of six distinct physiographic provinces, three of which are subdivided into different sections. Each province has its own economic advantages and geologic hazards and plays an important role in shaping everyday life in the state. They are: the Atlantic Coastal Plain Province, the Piedmont Province, the New England Province, the Ridge and Valley Province, the Appalachian Plateau Province, and the Central Lowlands Province.

Jacks Mountain mountain in United States of America

Jacks Mountain is a stratigraphic ridge in central Pennsylvania, United States, trending southeast of the Stone Mountain ridge and Jacks Mountain Anticline. The ridge line separates Kishacoquillas Valley from the Ferguson and Dry Valleys. Jacks Mountain lies in Mifflin, Huntingdon, Snyder, and Union Counties, and the ridge line forms part of the border between Huntingdon and Mifflin Counties.

Stone Mountain is a stratigraphic ridge in central Pennsylvania, United States, trending northwest of the Jacks Mountain ridge and Jacks Mountain Anticline. The ridge line separates Kishacoquillas Valley from the Seven Mountains area. Stone Mountain lies in, and the ridge line forms part of the border between, Mifflin and Huntingdon counties.

An antecedent stream is a stream that maintains its original course and pattern despite the changes in underlying rock topography. A stream with a dendritic drainage pattern, for example, can be subject to slow tectonic uplift. However, as the uplift occurs, the stream erodes through the rising ridge to form a steep-walled gorge. The stream thus keeps its dendritic pattern even though it flows over a landscape that will normally produce a trellis drainage pattern.

Gaps of the Allegheny

The gaps of the Allegheny, meaning gaps in the Allegheny Ridge in west-central Pennsylvania, is a series of escarpment eroding water gaps along the saddle between two higher barrier ridge-lines in the eastern face atop the Allegheny Ridge or Allegheny Front escarpment. The front extends south through Western Maryland and forms much of the border between Virginia and West Virginia, in part explaining the difference in cultures between those two post-Civil War states. While not totally impenetrable to daring and energetic travelers on foot, passing the front outside of the water gaps with even sure footed mules was nearly impossible without navigating terrain where climbing was necessary on slopes even burros would find extremely difficult.

3D fold evolution

In geology, 3D fold evolution is the study of the full three dimensional structure of a fold as it changes in time. A fold is a common three-dimensional geological structure that is associated with strain deformation under stress. Fold evolution in three dimensions can be broadly divided into two stages, namely fold growth and fold linkage. The evolution depends on fold kinematics, causes of folding, as well as alignment and interaction of the each structure with respect to each other. There are several ways to reconstruct the evolution progress of folds, notably by using depositional evidence, geomorphological evidence and balanced restoration. Understanding the evolution of folds is important because it helps petroleum geologists to gain a better understanding on the distribution of structural traps of hydrocarbon.

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