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Information about Valleys

This article is about the physical-geographic term. For places named "Valley" see Valley (disambiguation).


In geology, a valley is a depression with predominant extent in one direction. A very deep river valley may be called a canyon or gorge.

The terms U-shaped and V-shaped are descriptive terms of geography to characterize the form of valleys. Most valleys belong to one of these two main types or a mixture of them, at least with respect of the cross section of the slopes or hillsides.

River valleys

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Schematic cross section of a typical valley in the Eastern Alps. The shoulders of U or V valleys are often located roughly halfway up the slopes


A valley formed by flowing water, or river valley, is usually V-shaped. The exact shape will depend on the characteristics of the stream flowing through it. Rivers with steep gradients, as in mountain ranges, produce steep walls and a narrow bottom. Shallower slopes may produce broader and gentler valleys, but in the lowest stretch of a river, where it approaches its base level, it begins to deposit sediment and the valley bottom becomes a floodplain.

A V-shaped valley is formed by downcutting when the flowing stream erodes its channel at a higher rate than the sides are eroded. The resulting landform is a narrow canyon with fast water and little bank (floodplain) on the river sides.

Some broad V examples are:

Glacial valleys

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A glaciated valley in the Mount Hood Wilderness showing a characteristic U-shape and the broad shoulders
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U-shaped valley in Glacier National Park in Montana, United States.


A valley carved by glaciers, or glacial valley, is normally U-shaped. If we can see the valley, it means the glacier that formed it is no longer there. When the ice recedes or thaws, the valley remains, often littered with small boulders that were transported within the ice. Floor gradient does not affect the valley's shape, it is the glacier's size that does. Continuously flowing glaciers - espec. in the ice age - and large sized glaciers carve wide, deep incised valleys.

Examples of U-shaped valleys are found in every mountainous region that has experienced glaciation, usually during the Pleistocene ice ages. Most present U-shaped valleys started as V-shaped before glaciation. The glaciers carved it out wider and deeper, simultaneously changing the shape. This proceeds through the glacial erosion processes of (glaciation) and abrasion, which results in large rocky material (glacial till) being carried in the glacier. A material called boulder clay is deposited on the floor of the valley. As the ice melts and retreats, the valley is left with very steep sides and a wide, flat floor. A river or stream may remain in the valley. This replaces the original stream or river and is known as a misfit stream because it is smaller than one would expect given the size of its valley.

Other interesting glacially-carved valleys are the

Transition forms and valley shoulders

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Look from Paria View to a valley in Bryce Canyon/Utah with very striking shoulders


Depending on the topography, the rock types and the climate, a lot of transition forms between V-, U- and plain valleys exist. Their bottoms can be broad or narrow, but characteristic is also the type of valley shoulder. The broader a mountain valley, the lower its shoulders are located in most cases. An important exception are canyons where the shoulder almost is near the top of the valley's slope. In the Alps - e.g. the Tyrolean Inn valley - the shoulders are quite low (100-200 meters above the bottom). Many villages are located here (esp. at the sunny side) because the climate is very mild: even in winter when the valley's floor is completely filled with fog, these villages are in sunshine.

In some stress-tectonic regions of the Rockies or the Alps (e.g. Salzburg) the side valleys are parallel to each other, and additionally they are hanging. The brooks flow into the river in form of deep gorges or waterfalls. Usually this fact is the result of a violent erosion of the former valley shoulders. A special genesis we find also at arêtes and glacial cirques, at every Scottish glen, or a northern fjord.

Hanging valleys

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Bridal Veil Falls in Yosemite National Park flowing from a hanging valley.


A hanging valley is a tributary valley with the floor at a higher relief than the main channel into which it flows. They are most commonly associated with U-shaped valleys when a tributary glacier flows into a glacier of larger volume. The main glacier erodes a deep U-shaped valley with nearly vertical sides while the tributary glacier, with a smaller volume of ice, makes a shallower U-shaped valley. Since the surfaces of the glaciers were originally at the same elevation, the shallower valley appears to be ‘hanging’ above the main valley. Often, waterfalls form at or near the outlet of the upper valley. [1]

Valley floors

Usually the bottom of a main valley is broad - independent of the U or V shape. It typically ranges from about one to ten kilometres in width and is commonly filled with mountain sediments. The shape of the floor can be rather horizontal, similar to a flat cylinder, or terraced.

Side valleys are rather V than U-shaped; near the mouth clammies are possible if it is a hanging valley. The location of the villages depends on the across-valley profile, on climate and local traditions, and on the danger of avalanches or landslides. Predominant are places on terraces or alluvial fans if they exist.

Historic siting of villages within the mainstem valleys, however, have chiefly considered the potential of flooding.

Hollows

A hollow is a small valley or dry stream bed. This term is commonly used in New England, Arkansas, Missouri and Pennsylvania to describe such geographic features. Also used in Southern Appalachia, but pronounced "holler." Hollows may be formed by river valleys such as Mansfield Hollow or they may be relatively dry clefts with a notch-like characteristic in that they have a height of land and consequent water divide in their bases. A hollow such as this is Boston Hollow. Tourists in Europe can further visit a lot of karst, stalactite and ice hollows (e.g. in Slovenia and Austria).

Famous valleys

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A valley in the Blue Mountains

Rift valleys

Main article: Rift valley


Rift valleys, such as the Great Rift Valley, are formed by the expansion of the Earth's crust due to tectonic activity beneath the Earth's surface.

Extraterrestrial valleys

The other terrestrial planets and the moons of our Solar System can also have valley-like features. Lunar valleys can be formed from a linked chain of impact craters. Smaller valleys, known as rilles, may have originated from lava flows or from the contractions of cooling lava sheets.

Besides the lunar craters, the details of lunar mountain ranges have been well known for more than 300 years (e.g. J.H. Schröter's Selenotopographische Fragmente of 1791). A lot of linear phenomena like Rheita or Schröter valley and the famous Vallis Alpes (see also below) were observed with details less than 1 km (which corresponds to a coin seen from 5-10 km distance)—but the geological genesis was debated until the Apollo 11 mission in 1969. Astronomers have long been able to observe some highlands and mountains on Mars, and therefore guessed that there may be valleys, as well. In the 1970s this interpretation was proven correct by results from space probes. Valleys have also been found on Mercury and on the volcanic surfaces of Venus and Io.

The largest valley in our solar system is the Valles Marineris formation on Mars. The Valles (which were first detected in 1877 by Schiaparelli) are a huge canyon system spanning 4,500 x 600 km in area and having a depth up to 8 km. These enormous dimensions are 4-8 times greater than those of the American Grand Canyon. The Valles is currently understood to have been created by tectonic forces like the main grabens on Earth, rather than by running water. Later, though, it may have been expanded considerably by erosion, possibly including the action of surface water.

Icy moons of the gas planets Jupiter, Saturn and Neptune were also photographed by the two Voyagers as well as by other space probes. Some linear ruptures in the ice or apparent low areas between hills have been interpreted by astrogeologists as tectonic structures or valleys similar to grabens or active geologic rifts on Earth.

See also

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A view of Orosí, Costa Rica.

References

1. ^ Glossary of Glacier Terminology. U.S. Geological Survey (May 28, 2004). Retrieved on 2007-05-24.

External links

Extraterrestrial valleys

Valley is the name (or part of the name) of various places in the United States of America:
  • Valley, Alabama
  • Valley, Nebraska
  • Valley, Wyoming
  • Valley Center, California
  • Valley City, North Dakota
  • Valley Township, Armstrong County, Pennsylvania

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Oceanic crust      0-20 Ma
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Depression in geology is a landform sunken or depressed below the surrounding area. Depressions may be formed by various mechanisms, and may be referred to by a variety of technical terms.
  • A basin may be any large sediment filled depression.

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canyon (rarely cañon) or gorge is a deep valley between cliffs often carved from the landscape by a river. Most canyons were formed by a process of long-time erosion from a plateau level.
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geology, a valley is a depression with predominant extent in one direction. A very deep river valley may be called a canyon or gorge.

The terms U-shaped and V-shaped are descriptive terms of geography to characterize the form of valleys.
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Geography - (from the Greek words Geo (γη) or Gaea (γαία), both meaning "Earth", and graphein (γράφειν) meaning "to describe" or "to write"
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In geometry, a cross section is the intersection of a body in 2-dimensional space with a line, or of a body in 3-dimensional space with a plane, etc. More plainly, when cutting an object into slices one gets many parallel cross sections.
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river is a natural waterway that transits water through a landscape from higher to lower elevations. It is an integral component of the water cycle. The water within a river is generally collected from precipitation through surface runoff, groundwater recharge (as seen at baseflow
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For exotic financial options, see .


A mountain range is a chain of mountains bordered by lowlands or separated from other mountain ranges by passes or rivers.
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The base level of a river or stream is the lowest point to which it can flow, often referred to as the 'mouth' of the river. For large rivers, sea level is usually the base level, but a large river or lake is likewise the base level for tributary streams.
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A floodplain, or flood plain, is flat or nearly flat land adjacent to a stream or river that experiences occasional or periodic flooding.
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Downcutting, also called erosional downcutting or downward erosion or vertical erosion is a geological process that deepens the channel of a stream or valley by removing material from the stream's bed or the valley's floor.
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A floodplain, or flood plain, is flat or nearly flat land adjacent to a stream or river that experiences occasional or periodic flooding.
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Location Colorado, USA
Nearest city Montrose
Coordinates
Area 32,950 acres (133 km²)
Established October 21, 1999
Total visitation 160,450 (in 2006)
Governing body National Park Service
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Location Arizona, USA
Nearest city Flagstaff
Coordinates
Area 1,217,403.32 acres
  (1,180,862.78 federal)
4,926.
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Origin Radstädter Tauern (mountains)
Mouth Danube at Mauthausen
Basin countries Austria
Length 254 km (158 mi)
Source elevation  

Avg.
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The Napfgebiet is the hilly region lying between Berne and Lucerne. The region's highest elevation is the Napf with 1408 m ().
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Engadin or Engadine (German: Engadin, Rumantsch: Engiadina; tr: garden of the Inn) is a long mountain valley located in the canton of Graubünden in southeast Switzerland.
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Origin Grisons, Switzerland

Basin countries Switzerland, Liechtenstein, Austria, Germany, France, Netherlands
Length 1,320 km (820 mi)
Source elevation Vorderrhein: approx. 2,600 m (8,500 ft)
Hinterrhein: approx. 2,500 m (8,200 ft)

Avg.
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Origin Vosges mountains
Mouth Rhine
Basin countries France, Germany, Luxembourg, Belgium
Length 700km
Source elevation 715 m

Avg.
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glacier is a large, slow moving river of ice, formed from compacted layers of snow, that slowly deforms and flows in response to gravity. Glacier ice is the largest reservoir of fresh water on Earth, and second only to oceans as the largest reservoir of total water.
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ice age is a period of long-term reduction in the temperature of Earth's climate, resulting in an expansion of the continental ice sheets, polar ice sheets and mountain glaciers.
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glacier is a large, slow moving river of ice, formed from compacted layers of snow, that slowly deforms and flows in response to gravity. Glacier ice is the largest reservoir of fresh water on Earth, and second only to oceans as the largest reservoir of total water.
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Pleistocene epoch (IPA: /'plaɪstəsi:n/) on the geologic timescale is the period from 1,808,000 to 11,550 years BP. The Pleistocene epoch had been intended to cover the world's recent period of repeated glaciations.
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ice age is a period of long-term reduction in the temperature of Earth's climate, resulting in an expansion of the continental ice sheets, polar ice sheets and mountain glaciers.
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Plucking describes the process of removing human hair, animal hair, or a bird's feathers by mechanically pulling the item from the owner's body.

In humans, this is done for personal grooming purposes, usually with tweezers. An epilator is a motorised hair plucker.
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abrasion, is superficial damage to the skin, generally not deeper than the epidermis. It is more superficial than an excoriation, although it can give mild bleeding. Mild abrasions, also known as 'grazes' do not scar, but deep abrasions may lead to the development of scarring
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river is a natural waterway that transits water through a landscape from higher to lower elevations. It is an integral component of the water cycle. The water within a river is generally collected from precipitation through surface runoff, groundwater recharge (as seen at baseflow
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This article or section deals primarily with the United Kingdom and does not represent a worldwide view of the subject.
Please [ improve this article] or discuss the issue on the talk page.

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misfit stream (or underfit stream) is a stream that is far too small to have eroded the valley which the stream occupies. The shape of the valley may also be inconsistent with a typical valley that has been eroded by water.
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