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geography Geography (from Greek: , ''geographia'', literally "earth description") is a field of science devoted to the study of the lands, features, inhabitants, and phenomena of the Earth and planets. The first person to use the word γεωγραφ ...
, an oasis (, plural oases, ) is a fertile area (often having a
date palm ''Phoenix dactylifera'', commonly known as date or date palm, is a flowering plant species in the palm family, Arecaceae, cultivated for its edible sweet fruit. The species is widely cultivated across Northern Africa, the Middle East and South A ...
grove) in a
desert upright=1.5, alt=see caption, Sand dunes in the Rub' al Khali ("Empty quarter") in the United Arab Emirates A desert is a barren area of landscape where little precipitation occurs and, consequently, living conditions are hostile for ...
or semi-desert environment.Battesti, Vincent (2005) Jardins au désert: Évolution des pratiques et savoirs oasiens: Jérid tunisien. Paris: IRD éditions.
. Oases also provide habitats for animals and plants.


Etymology

The word ''oasis'' came into English from la, oasis, from grc, ὄασις, , which in turn is a direct borrowing from
Demotic Egyptian Demotic (from grc, δημοτικός ''dēmotikós'', 'popular') is the ancient Egyptian script derived from northern forms of hieratic used in the Nile Delta, and the stage of the Egyptian language written in this script, following Late Egyptian ...
. The word for ''oasis'' in the later attested
Coptic language#REDIRECT Coptic language#REDIRECT Coptic language {{Redirect category shell, 1= {{R from other capitalisation ...
{{Redirect category shell, 1= {{R from other capitalisation ...
(the descendant of Demotic Egyptian) is ''wahe'' or ''ouahe'' which means a "dwelling place".


Description

Oases are made fertile when sources of freshwater, such as underground rivers or
aquifer An aquifer is an underground layer of water-bearing permeable rock, rock fractures or unconsolidated materials (gravel, sand, or silt). Groundwater can be extracted using a water well. The study of water flow in aquifers and the characterization ...
s, irrigate the surface naturally or via man-made wells. The presence of water on the surface or underground is necessary and the local or regional management of this essential resource is strategic, but not sufficient to create such areas: continuous human work and know-how (a technical and social culture) are essential to maintain such ecosystems.Vincent Battesti, The Power of a Disappearance: Water in the Jerid region of Tunisia ''in'' B. R. Johnston ''et al.'' (eds), ''Water, Cultural Diversity & Global Environmental Change: Emerging Trends, Sustainable Futures?'', 2012, UNESCO/Springer,
.Vincent Battesti, Resources and Appropriations: Back to the Jerid Oases (Tunisia) after the Revolution, ''Études rurales'' 2015, vol. 2013/2 (192): 153-175
 Rain showers provide subterranean water to sustain natural oases, such as the
Tuat Tuat, or Touat, is a natural region of desert in central Algeria that contains a string of small oases. In the past, the oases were important for caravans crossing the Sahara. Geography Tuat lies to the south of the Grand Erg Occidental, to the ...
. Substrata of impermeable rock and stone can trap water and retain it in pockets, or on long faulting subsurface ridges or volcanic dikes water can collect and percolate to the surface. Any incidence of water is then used by
migrating bird Bird migration is the regular seasonal movement, often north and south along a flyway, between breeding and wintering grounds. Many species of bird migrate. Migration carries high costs in predation and mortality, including from hunting by human ...
s, which also pass seeds with their droppings which will grow at the water's edge forming an oasis. It can also be used to plant crops.


Historical significance

The location of oases has been of critical importance for trade and transportation routes in desert areas; caravans must travel via oases so that supplies of water and food can be replenished. Thus, political or military control of an oasis has in many cases meant control of trade on a particular route. For example, the oases of
Awjila Awjila (Berber: ''Awilan'', ''Awjila'', ''Awgila''; ar, أوجلة; Latin: ''Augila'') is an oasis town in the Al Wahat District in the Cyrenaica region of northeastern Libya. Since classical times it has been known as a place where high quality da ...
, Ghadames and Kufra, situated in modern-day Libya, have at various times been vital to both north–south and east–west Trans-Saharan trade, trade in the Sahara Desert. The Silk Road across Central Asia also incorporated several oases. In North American history, oases have been less prominent since the desert regions are smaller, however several areas in the deep southwestern United States have oases regions that served as important links through the hot deserts and vast rural areas. While present day desert cities like Las Vegas, Phoenix, Arizona, Phoenix, Palm Springs, and Tucson are large modern cities, many of these locations were once small, isolated farming areas at which travelers through the western desert stopped for food and supplies. Even today, there are several roads that go through western deserts like U.S. Route 50 through southern Nevada, and the Mojave Desert that feature small green fields, citrus groves and small isolated supply towns.


Growing plants

People who live in an oasis must manage land and water use carefully; fields must be irrigated to grow plants like apricots, Date palm, dates, Common fig, figs, and olives. The most important plant in an oasis is the date palm, which forms the upper layer. These palm trees provide shade for smaller trees like peach trees, which form the middle layer. By growing plants in different layers, the farmers make best use of the soil and water. Many vegetables are also grown and some cereals, such as barley, millet, and wheat, are grown where there is more moisture. In summary, an oasis palm grove is a highly anthropized and irrigated area that supports a traditionally intensive and polyculture-based agriculture. The oasis is integrated into its desert environment through an often close association with nomadic transhumant livestock farming (very often pastoral and sedentary populations are clearly distinguished). However, the oasis is emancipated from the desert by a very particular social and ecosystem structure. Responding to environmental constraints, it is an integrated agriculture that is conducted with the superposition (in its typical form) of two or three strata creating what is called the "oasis effect": * the first and highest stratum is made up of date palms (date palm, ''Phoenix dactylifera'' L.) and maintains freshness; * an intermediate stratum includes fruit trees (orange, banana, pomegranate, apple, etc.); * the third stratum, in the shade, of herbaceous plants (market gardening, fodder, cereals).


Gallery

File:Jabal Al Qara Cave - Al Hassa, Saudi Arabia ജബൽ അൽ ഖാറ ഗുഹ, അൽ ഹസ, സൗദി അറേബ്യ 13.JPG, Al-Ahsa Oasis, also known as Al-Hasa Oasis, in Saudi Arabia is the largest oasis in the world File:Al Ain Oasis, Al Mutawaa - Abu Dhabi - United Arab Emirates - panoramio.jpg, Al Ain Oasis in the city of Al Ain in the United Arab Emirates File:AG 006 large.jpg, Taghit in Algeria, North Africa File:ArugotRiver.jpg, Ein Gedi in Israel, Middle East File:Fish Springs Utah.jpg, Fish Springs National Wildlife Refuge in Utah, United States File:Rubaksa gardens.jpg, Rubaksa in a dry limestone environment in north Ethiopia is an oasis thanks to the existence of karstic springs File:29 Palms Sign.jpg, Twentynine Palms sign File:Red Rock Canyon National Conservation Area view 031513.JPG, Creosote (''Larrea tridentata'') on alluvium at Red Rock Canyon National Conservation Area, southern Nevada. United States File:Crescent_Moon_Lake_(23889572731).jpg, Crescent Lake (Dunhuang), Crescent Lake (Yueyaquan) in the Gobi Desert


See also

* – the world's largest irrigation project; developed in Libya to connect cities with fossil water. * * * * ** * *


References


Bibliography

*


External links

* {{Authority control Oases, Lacustrine landforms Physical geography