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Valley

earth science Maturity 11-13 Next article →

A valley is an elongated low area in the landscape. It often runs between hills or mountains. Most valleys are longer than they are wide. They can take on many different dimensions and shapes. Many valleys contain a river or stream running through them.

Palakaria-and-Belchin-3
Palakaria-and-Belchin-3

The flat or relatively flat portion between the sides is called the valley floor. This floor is typically formed by river sediments. It may also be flanked by fluvial terraces.

Halikonjokilaakso
Halikonjokilaakso

Most valleys are created through erosion over very long periods. This process is common in river valleys. Water alters the surface through corrasion, abrasion, pot-holing, corrosion, and weathering. In the upper valley, a stream erodes its bed through corrasion. This produces a steep-sided V-shaped valley. As the stream moves to the middle valley, it becomes wider. Numerous streams often coalesce here. The flow slows down, and both erosion and deposition occur.

In the middle section, lateral erosion becomes more common. Strong currents on the outside of a curve erode the bank. Conversely, deposition happens on the inside of curves where the current is slacker. This process can lead to a meandering character. In the lower valley, the gradient decreases. Meanders may become much broader. This can result in a broad floodplain. In these lower areas, deposition dominates over erosion.

DirkvdM orosi
DirkvdM orosi

Glaciers also carve distinct types of valleys. These are often called glacial troughs. They typically have a U-shaped profile in cross-section. This shape is caused by glacial erosion removing contact surfaces. This process minimizes friction. The uppermost part of these valleys often contains cirques. These are armchair-shaped hollows excavated by rotational movement.

Tal-y-llyn-valley-Dolgoch-01
Tal-y-llyn-valley-Dolgoch-01

Abrasion by rock material in the ice deepens and widens the valley. This creates steep sides and a flat bottom. Some glacial valleys may even feature ribbon lakes. In coastal areas, these features are known as fjords.

Hanging valleys are a specific type of tributary valley. They are higher than the main valley. This occurs most commonly in U-shaped glacial landscapes. A large glacier erodes a deep main valley. A smaller tributary glacier makes a shallower valley. Because the glaciers were originally at the same elevation, the smaller one appears to be hanging.

Closeup of Bridalveil Fall seen from Tunnel View in Yosemite NP
Closeup of Bridalveil Fall seen from Tunnel View in Yosemite NP

This often results in waterfalls at the outlet. Hanging valleys can also form due to varying rates of erosion in different rock types.

Ибърско езеро
Ибърско езеро

Some valleys do not form through erosion at all. Rift valleys arise from tectonic processes. These are caused by the expansion of the Earth's crust. This movement happens due to tectonic activity beneath the surface. Examples of these include the Albertine Rift and the Gregory Rift. Other unique forms exist, such as tunnel valleys. These are large, U-shaped valleys cut under glacial ice. They were formed by subglacial water erosion. They once served as drainage pathways for massive volumes of meltwater.

Pirin ezera Pano Chairski ezera
Pirin ezera Pano Chairski ezera

Geographers use many specific terms to describe these landforms. A canyon or gorge is a deep cleft between cliffs. An arroyo is a dry watercourse that fills after rain. A dell is a small, secluded, and often wooded valley. In the Appalachian Mountains, a small valley might be called a cove. These terms help scientists categorize the diverse morphology of the Earth. Understanding these processes shows how water, ice, and tectonic forces shape our world.

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🖼️ Images & Media (14)
File:Halikonjokilaakso.jpg
Halikonjokilaakso.jpg
File:Palakaria-and-Belchin-3.jpg
Palakaria-and-Belchin-3.jpg
File:Tal-y-llyn-valley-Dolgoch-01.jpg
Tal-y-llyn-valley-Dolgoch-01.jpg
File:Glacial Valley MtHoodWilderness.jpg
Glacial Valley MtHoodWilderness.jpg
File:Pirin ezera Pano Chairski ezera.jpg
Pirin ezera Pano Chairski ezera.jpg
File:Paria View at Bryce Canyon NP.jpg
Paria View at Bryce Canyon NP.jpg
File:Closeup of Bridalveil Fall seen from Tunnel View in Yosemite NP.JPG
Closeup of Bridalveil Fall seen from...
File:Ибърско езеро.jpg
Ибърско езеро.jpg
File:Indus Kohistan Pakistan.jpg
Indus Kohistan Pakistan.jpg
File:DirkvdM orosi.jpg
DirkvdM orosi.jpg
File:"Flowers Blossom at Valley of Flowers Chamoli, India" 58.jpg
"Flowers Blossom at Valley of Flowers...
File:Harau valley.jpg
Harau valley.jpg

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