Valley
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A valley is an elongated low area often running between hills or mountains, which will typically contain a river or stream running from one end to the other. Most valleys are formed by erosion of the land surface by rivers or streams over a very long period. Some valleys are formed through erosion by glacial ice. These glaciers may remain present in valleys in high mountains or polar areas.
At lower latitudes and altitudes, these
Formation of valleys
Valleys may arise through several different processes. Most commonly, they arise from
River valleys
The development of a river valley is affected by the character of the bedrock over which the river or stream flows, the elevational difference between its top and bottom, and indeed the climate. Typically the flow will increase downstream and the gradient will decrease. In the upper valley, the stream will most effectively erode its bed through corrasion to produce a steep-sided V-shaped valley. The presence of more resistant rock bands, of geological faults, fractures, and folds may determine the course of the stream and result in a twisting course with interlocking spurs.
In the middle valley, as numerous streams have coalesced, the valley is typically wider, the flow slower and both erosion and deposition may take place. More lateral erosion takes place in the middle section of a river's course, as strong currents on the outside of its curve erode the bank. Conversely, deposition may take place on the inside of curves where the current is much slacker, the process leading to the river assuming a meandering character. In the lower valley, gradients are lowest, meanders may be much broader and a broader floodplain may result. Deposition dominates over erosion.[1][2] A typical river basin or drainage basin will incorporate each of these different types of valleys.
Some sections of a stream or river valleys may have vertically incised their course to such an extent that the valley they occupy is best described as a
Glacial valleys
There are various forms of valleys associated with glaciation. True glacial valleys are those that have been cut by a glacier which may or may not still occupy the valley at the present day. Such valleys may also be known as glacial troughs. They typically have a U-shaped cross-section and are characteristic landforms of mountain areas where glaciation has occurred or continues to take place.[4]
The uppermost part of a glacial valley frequently consists of one or more 'armchair-shaped' hollows, or '
Interlocking spurs associated with the development of river valleys are preferentially eroded to produce truncated spurs, typical of glaciated mountain landscapes. The upper end of the trough below the ice-contributing cirques may be a trough-end. Valley steps (or 'rock steps') can result from differing erosion rates due to both the nature of the bedrock (hardness and jointing for example) and the power of the moving ice. In places, a rock basin may be excavated which may later be filled with water to form a ribbon lake or else by sediments. Such features are found in coastal areas as fjords. The shape of the valley which results from all of these influences may only become visible upon the recession of the glacier that forms it.[5] A river or stream may remain in the valley; if it is smaller than one would expect given the size of its valley, it can be considered an example of a misfit stream.
Other interesting glacially carved valleys include:
- Yosemite Valley (United States)
- Side valleys of the Austrian river Salzach for their parallel directions and hanging mouths.
- That of the Glacier National Park in Montana, United States.
Tunnel
A tunnel valley is a large, long, U-shaped valley originally cut under the glacial ice near the margin of continental ice sheets such as that now covering Antarctica and formerly covering portions of all continents during past glacial ages.
Meltwater
In northern Central Europe, the Scandinavian ice sheet during the various ice ages advanced slightly uphill against the lie of the land. As a result, its meltwaters flowed parallel to the ice margin to reach the North Sea basin, forming huge, flat valleys known as
Transition forms and shoulders
Depending on the
In some stress-tectonic regions of the
Hanging tributary
A hanging valley is a tributary valley that is higher than the main valley. They are most commonly associated with U-shaped valleys, where 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.[7]
Hanging valleys also occur in
Glaciated terrain is not the only site of hanging streams and valleys. Hanging valleys are also simply the product of varying rates of erosion of the main valley and the tributary valleys. The varying rates of erosion are associated with the composition of the adjacent rocks in the different valley locations. The tributary valleys are eroded and deepened by glaciers or erosion at a slower rate than that of the main valley floor; thus the difference in the two valleys' depth increases over time. The tributary valley, composed of more resistant rock, then hangs over the main valley.[9]
Trough-shaped
Trough-shaped valleys also form in regions of heavy topographic
Box
Box valleys have wide, relatively level floors and steep sides. They are common in periglacial areas and occur in mid-latitudes, but also occur in tropical and arid regions.[11]
Rift
Rift valleys, such as the Albertine Rift and Gregory Rift are formed by the expansion of the Earth's crust due to tectonic activity beneath the Earth's surface.
Terms for valleys
There are many terms used for different sorts of valleys. They include:
- Cove: A small valley, closed at one or both ends, in the central or southern Appalachian Mountains which sometimes results from the erosion of a geologic window.
- Dell: A small, secluded, and often wooded valley.
- Dry valley: A valley not created by sustained surface water flow.
- Erosional valley: A valley formed by erosion.
- Hollow: A term used regionally for a small valley surrounded by mountains or ridges. In Ireland, New England, Appalachia, and the Ozarks of Arkansas and Missouri, a hollow is a small valley or dry stream bed.
- Longitudinal valley: An elongated valley found between two nearly-parallel mountain chains.
- Steephead valley: A deep, narrow, flat-bottomed valley with an abrupt ending.
- Strike valley: A valley typically developed parallel to a cuesta from more readily eroded strata.
- Structural valley: A valley formed by geologic events such as drop faults or the rise of highlands.[12]
Similar geographical features such as gullies, chines, and kloofs, are not usually referred to as valleys.
British regional terms for valleys
The terms
The word dale occurs widely in place names in the north of England and, to a lesser extent, in southern Scotland. As a generic name for a type of valley, the term typically refers to a wide valley, though there are many much smaller stream valleys within the Yorkshire Dales which are named "(specific name) Dale".[17] Clough is a word in common use in northern England for a narrow valley with steep sides.[18] Gill is used to describe a ravine containing a mountain stream in Cumbria and the Pennines.[19] The term combe (also encountered as coombe) is widespread in southern England and describes a short valley set into a hillside.[20] Other terms for small valleys such as hope, dean, slade, slack and bottom are commonly encountered in place-names in various parts of England but are no longer in general use as synonyms for valley.
The term vale is used in England and Wales to describe a wide river valley, usually with a particularly wide
Human settlement
Some of the first human
Notable examples
Africa
- Albertine Rift
- East African Rift
- Ethiopian Rift Valley
- Great Rift Valley
- Nile Valley(Egypt/Sudan/Ethiopia/Uganda)
- Nugaal Valley (Somalia)
- Umba Valley (Tanzania)
- Valley of the Kings (Egypt)
Asia
- List of valleys in India
- List of valleys in Pakistan
- Beqaa Valley (Lebanon)
- Emin Valley (Kazakhstan)
- Ihlara, Turkey
- Dang Valley (Western Nepal)
- Jordan Rift Valley (Jordan - Israel)
- Jordan Valley
- Kathmandu (Nepal)
- Klang Valley (Malaysia)
- Mahaweli(Sri Lanka)
- Panjshir Valley (Afghanistan)
- Valleys of China
- Baligou Valley
- Emin Valley
- Heizhu Valley
- Insukati Valley
- Jiuzhaigou Valley
- Mutou Valley
Oceania
- Barossa Valley (Australia)
- Bulolo Valley (Papua New Guinea)
- Cagayan Valley (Philippines)
- Capertee Valley (Australia)
- Hunter Valley(Australia)
- Hutt Valley (New Zealand)
- kangaroo Valley(Australia)
- Markham Valley (Papua New Guinea)
- Strath Taieri (New Zealand)
- Swan Valley(Australia)
Europe
- Dalen, Telemark (Telemark, Norway)
- Bergensdalen (Vestland, Norway)
- Danube Valley(Eastern Europe)
- Glen Coe (Scotland, United Kingdom)
- Great Glen (Scotland, United Kingdom)
- Gudbrandsdalen (Oppland, Norway)
- Hallingdalen(Buskerud, Norway)
- Heddal (Telemark, Norway)
- Iron Gate(Romania/Serbia)
- Lauterbrunnen Valley(Bern, Switzerland)
- Loire Valley with its famous castles (France)
- Midt-Telemark (Telemark, Norway)
- Nant Ffrancon(Wales, United Kingdom)
- Numedalen(Buskerud, Norway)
- Østerdalen (Hedmark, Norway)
- Po Valley, (Italy)
- Rhone Valley from the Matterhorn to Grenoble and Lyon(France)
- Romsdalen (Møre Og Romsdal, Norway)
- Setesdal (Agder, Norway)
- South Wales Valleys (Wales, United Kingdom)
- Upper Rhine Valley or Upper Rhine Plain, an old graben system. (France and Germany)
- Vestfjorddalen (Norway)
- Evrotas Valley, Sparta (Greece)
North America
- Caguas (Puerto Rico)
- Central Valley (California)
- Coachella Valley (California)
- Cumberland Valley (Maryland/Pennsylvania)
- Cuyahoga Valley (Ohio)
- Death Valley (California)
- Fraser Canyon (British Columbia)
- Fraser Valley (British Columbia)
- Grand Canyon (Arizona, United States)
- Hell's Gate(British Columbia)
- Hudson Valley (New York)
- Imperial Valley (California)
- Las Vegas Valley (Nevada)
- Missouri River Valley (Missouri)
- Monument Valley (Arizona, Utah)
- Napa Valley (California)
- Okanagan Valley(British Columbia)
- Ottawa Valley (Ontario/Quebec)
- Palo Duro Canyon (Texas)
- Valley of the Sun (Arizona)
- Rio Grande Valley(Texas)
- Saint Lawrence Valley(Ontario/Quebec/New York)
- Salt Lake Valley (Utah)
- San Fernando Valley (California)
- Shenandoah Valley (Virginia/West Virginia)
- Sonoma Valley (California)
- Toluca Valley (Mexico)
- Valley of the Gods (Utah)
- Valley of Mexico (Mexico)
- Willamette Valley (Oregon)
- Yosemite Valley (California)
South America
- Aburra Valley(Colombia)
- Calchaquí Valleys (Argentina)
- Paraíba Valley (Brazil)
- Cauca Valley (Colombia)
- IschigualastoValley of the Moon (Argentina)
Antarctica
Extraterrestrial valleys
Numerous elongate depressions have been identified on the surface of Mars, Venus, the Moon, and other planets and their satellites and are known as valles (singular: 'vallis'). Deeper valleys with steeper sides (akin to canyons) on certain of these bodies are known as chasmata (singular: 'chasma'). Long narrow depressions are referred to as fossae (singular: 'fossa').[21] These are the Latin terms for 'valley, 'gorge' and 'ditch' respectively. The German term 'rille' or Latin term 'rima' (signifying 'cleft') is used for certain other elongate depressions on the Moon.[22]
See also:
- List of valleys on Mars
- List of chasmata on Mars
- List of valleys on the Moon
- List of largest rifts, canyons and valleys in the Solar System
See also
- Canyon – Deep chasm between cliffs
- Grass valley – Meadow within a forested and relatively small drainage basin
- Gully – Landform created by running water and/or mass movement eroding sharply into soil
- Stream channel – Type of landform in which part of a body of water is confined to a relatively narrow but long region
References
- ISBN 0340090227.
- OCLC 2968.
- ISBN 0340090227.
- ^ "Vale of Eden". Britannica. Retrieved 20 December 2020.
- ISBN 0340090227.
- .
- ^ "Glossary of Glacier Terminology". U.S. Geological Survey. May 28, 2004. Retrieved 2007-05-24.
- ^ Nesje, A., & Whillans, I. M. (1994). Erosion of Sognefjord, Norway. Geomorphology, 9(1), 33-45.
- ^ "Illustrated Glossary of Alpine Glacial Landforms - Hanging Valley". .uwsp.edu. Retrieved 2011-10-03.
- ISBN 978-0-444-63369-9, retrieved 2023-10-19
- ISBN 9780415327381.
- ^ "Early History, Santa Clara County". National Park Service. Retrieved January 16, 2015.
Santa Clara Valley is a structural valley, created by mountain building, as opposed to an erosional valley, or one which has undergone the wearing away of the earth's surface by natural agents.
- ISBN 1841581739.
- ISBN 1841581739.
- ISBN 1841581739.
- ISBN 0140510494.
- ^ "Bing maps". Microsoft Bing. Retrieved 20 December 2020.
- ISBN 0460860860.
- ISBN 0460860860.
- ^ "Combe". Merriam–Webster's Dictionary. Merriam–Webster. 2011.
- ^ "Gazetteer of Planetary Nomenclature, feature types". International Astronomical Union. Retrieved 20 December 2020.
- ^ "Gazetteer of Planetary Nomenclature, Welcome". International Astronomical Union. Retrieved 20 December 2020.
External links
- NPS.gov, University of Wisconsin
- UWSP.edu, Glossary of Alpine Glacial Landforms
- "BGU.ac.il" (PDF)., SAR interferometry (analysis of valley forms in Fig.2 and 6)
- Valleys.com, Valleys of the World
- Valley definitions, YourDictionary
Extraterrestrial valleys
- ESA image: Vallis Alpes, bisecting the Lunar Alps
- Valles Marineris and Ophir Chasma, )