From Wikipedia, the free encyclopedia
Largest non-polar deserts
A
desert is a
landscape or
region that receives an extremely low amount of
precipitation, less than enough to support growth of most plants. Deserts are defined as areas with an average annual precipitation of less than 250 millimetres (10 in) per year,
[1][2] or as areas where more water is lost by
evapotranspiration than falls as precipitation.
[3] In the
Köppen climate classification system, deserts are classed as
BWh (hot desert) or
BWk (temperate desert). In the Thornthwaite climate classification system, deserts would be classified as arid
megathermal climates.
[4][5]
[edit] Geography
A satellite image of the
Sahara, the world's largest hot desert.
The snow surface at Dome C Station in Antarctica is representative of the majority of the continent's surface.
Deserts are part of a wide classification of regions that, on an average annual basis, have a moisture deficit (i.e. they can potentially lose more than is received). Deserts are located where vegetation cover is sparse to almost nonexistent.
[1][6] Deserts take up about one fifth (20%) of the Earth's land surface.
[1] Hot deserts usually have a large
diurnal and seasonal temperature range, with high daytime temperatures, and low nighttime temperatures (due to extremely low
humidity). In hot deserts the temperature in the daytime can reach 45 °C/113 °F or higher in the summer, and dip to 0 °C/32 °F or lower at nighttime in the winter. Water vapor in the atmosphere acts to trap
infrared radiation from both the sun and the ground, and dry desert air is incapable of blocking
sunlight during the day or
trapping heat during the night. Thus, during daylight most of the
sun's heat reaches the ground, and as soon as the sun sets the desert cools quickly by radiating its heat into space. Urban areas in deserts lack large (more than 14 °C/25 °F) daily temperature variations, partially due to the
urban heat island effect.
Many deserts are formed by
rain shadows; mountains blocking the path of precipitation to the desert (on the lee side of the mountain). Deserts are often composed of
sand and
rocky surfaces.
Sand dunes called
ergs and stony surfaces called
hamada surfaces compose a minority of desert surfaces. Exposures of
rocky terrain are typical, and reflect minimal soil development and sparseness of
vegetation. The soil is rocky because of the low chemical weathering.
Bottomlands may be
salt-covered flats.
Eolian processes are major factors in shaping desert landscapes.
Polar deserts (also seen as "cold deserts") have similar features, except the main form of precipitation is
snow rather than
rain.
Antarctica is the world's largest cold desert (composed of about 98 percent thick
continental ice sheet and 2 percent barren rock). Some of the barren rock is to be found in the so-called
Dry Valleys of Antarctica that almost never get snow, which can have ice-encrusted
saline lakes that suggest evaporation far greater than the rare snowfall due to the strong
katabatic winds that evaporate even ice.
The largest hot desert is the Sahara in northern Africa, covering 9 million square kilometres and 12 countries.
Deserts sometimes contain valuable mineral deposits that were formed in the arid environment or that were exposed by erosion. Due to extreme and consistent dryness, some deserts are ideal places for natural preservation of artifacts and fossils.
The largest deserts
| Rank | Desert | Area (km²) | Area (mi²) |
|---|
| 1 | Antarctic Desert (Antarctica) | 13,829,430 | 5,339,573 |
| 2 | Sahara (Africa) | 9,100,000+ | 3,320,000+ |
| 3 | Arabian Desert (Middle East) | 2,330,000 | 900,000 |
| 4 | Gobi Desert (Asia) | 1,300,000 | 500,000 |
| 5 | Kalahari Desert (Africa) | 900,000 | 360,000 |
| 6 | Patagonian Desert (South America) | 670,000 | 260,000 |
| 7 | Great Victoria Desert (Australia) | 647,000 | 250,000 |
| 8 | Syrian Desert (Middle East) | 520,000 | 200,000 |
| 9 | Great Basin Desert (North America) | 492,000 | 190,000 |
[edit] Etymology
English
desert and its
Romance cognates (including
Italian and
Portuguese deserto,
French désert and
Spanish desierto) all come from the
ecclesiastical Latin dēsertum (originally "an abandoned place"), a participle of
dēserere, "to abandon." (See
desertion.) The correlation between aridity and sparse population is complex and dynamic, varying by culture, era, and technologies; thus the use of the word
desert can cause confusion. In English prior to the 20th century,
desert was often used in the sense of "unpopulated area", without specific reference to aridity; but today the word is most often used in its climate-science sense (an area of low precipitation)—and a desert may be quite heavily populated, with millions of inhabitants. Phrases such as "
desert island" and "
Great American Desert" in previous centuries did not necessarily imply sand or aridity; their focus was the sparse population. However, the connotation of a hot, parched, and sandy place often influences today's popular interpretation of those phrases.
[edit] Classification
In 1961,
Peveril Meigs divided desert regions on Earth into three categories according to the amount of precipitation they received. In this now widely accepted system, extremely arid lands have at least 12 consecutive months without rainfall, arid lands have less than 250 mm (10 in) of annual rainfall, and semiarid lands have a mean annual precipitation of between 250 and 500 mm (10–20 in). Arid and extremely arid lands are deserts, and semiarid areas are generally referred to as
steppes.
[1]
[edit] Definition
Measurement of
rainfall alone cannot provide an accurate definition of what a desert is because being arid also depends on evaporation, which depends in part on
temperature. For example,
Phoenix, Arizona receives less than 250 millimeters (10 in) of precipitation per year, and is immediately recognized as being located in a desert due to its arid adapted plants. The
North Slope of Alaska's
Brooks Range also receives less than 250 millimeters (10 in) of precipitation per year and is often classified as a cold desert.
[7] Other regions of the world have cold deserts, including areas of the
Himalayas[8] and other high altitude areas in other parts of the world.
[9] Polar deserts cover much of the ice free areas of the arctic and Antarctic.
[10][11]
Potential
evapotranspiration supplements the measurement of rainfall in providing a scientific measurement-based definition of a desert. The water budget of an area can be calculated using the formula
P −
PE ±
S, wherein
P is precipitation,
PE is potential evapotranspiration rates and
S is amount of surface storage of water. Evapotranspiration is the combination of water loss through atmospheric
evaporation and through the life processes of plants. Potential evapotranspiration, then, is the amount of water that
could evaporate in any given region. As an example,
Tucson, Arizona receives about 300 millimeters (12 in) of rain per year, however about 2500 millimeters (100 in) of water could evaporate over the course of a year.
[citation needed] In other words, about 8 times more water could evaporate from the region than actually falls. Rates of evapotranspiration in cold regions such as Alaska are much lower because of the lack of heat to aid in the evaporation process.
There are different forms of deserts. Cold deserts can be covered in
snow or
ice; frozen water unavailable to plant life. These are more commonly referred to as
tundra if a short season of above-freezing temperatures is experienced, or as an
ice cap if the temperature remains below freezing year-round, rendering the land almost completely lifeless.
Most non-polar deserts are hot in the day and chilly at night (for the latitude) because of the lack of the moderating effect of water. In some parts of the world, deserts are created by a
rain shadow effect in which air masses lose much of their moisture as they move over a
mountain range; other areas are arid by virtue of being very far from the nearest available sources of moisture.
Deserts are also classified by their geographical location and dominant weather pattern as trade wind, mid-latitude, rain shadow, coastal, monsoon, or
polar deserts. Former desert areas presently in non-arid environments are paleodeserts.
Montane deserts are arid places with a very high
altitude; the most prominent example is found north of the
Himalayas, especially in Ladakh region of Jammu and Kashmir, in parts of the
Kunlun Mountains and the
Tibetan Plateau. Many locations within this category have elevations exceeding 3,000 meters (10,000 ft) and the thermal regime can be
hemiboreal. These places owe their profound aridity (the average annual precipitation is often less than 40 mm or 1.5 in) to being very far from the nearest available sources of moisture. Montane deserts are normally cold.
Rain shadow deserts form when tall mountain ranges block clouds from reaching areas in the direction the wind is going. As the air moves over the mountains, it cools and moisture condenses, causing
precipitation on the windward side. When that air reaches the leeward side, it is dry because it has lost the majority of its moisture, resulting in a desert. The air then warms, expands, and blows across the desert. The warm, desiccated air takes with it any remaining moisture in the desert.
[edit] Desert features
Satellite view of
Al-Dahna desert in Saudi Arabia showing different depositional features
covers only about 20 percent of Earth's deserts. Most of the sand is in sand sheets and sand seas—vast regions of undulating dunes resembling ocean waves "frozen" in an instant of time. In general, there are five forms of deserts:
- Mountain and basin deserts
- Hamada deserts, which consist of plateau landforms
- Regs, which consist of rock pavements
- Ergs, which are formed by sand seas
- Intermontane Basins
Nearly all desert surfaces are plains where eolian deflation—removal of fine-grained material by the wind—has exposed loose gravels consisting predominantly of
pebbles but with occasional
cobbles.
The remaining surfaces of arid lands are composed of exposed
bedrock outcrops,
desert soils, and
fluvial deposits including
alluvial fans,
playas, desert
lakes, and oases. Bedrock outcrops occur as small mountains surrounded by extensive erosional plains.
Several different types of dunes exist. Barchan dunes are produced by strong winds blowing across a level surface and are crescent-shaped. Longitudinal or seif dunes are dunes that are parallel to a strong wind that blows in one general direction. Transverse dunes run at a right angle to the constant wind direction. Star dunes are star-shaped and have several ridges that spread out around a point.
Oases are vegetated areas moistened by
springs,
wells, or by
irrigation. Many are artificial. Oases are often the only places in deserts that support crops and permanent habitation.
[edit] Fauna and flora
Organ Pipe cactus in Arizona
Flora of Baja California Desert, Cataviña region, Mexico
Deserts have a reputation for supporting very little life, but in reality deserts often have high
biodiversity, including
animals that remain hidden during daylight hours to control body temperature or to limit moisture needs. Some fauna includes the
kangaroo rat,
coyote,
jack rabbit, and many
lizards. These animals adapted to live in deserts are called
xerocoles. Many desert animals (and plants) show especially clear evolutionary adaptations for water conservation or heat tolerance, and so are often studied in
comparative physiology,
ecophysiology, and
evolutionary physiology. One well-studied example is the specializations of mammalian kidneys shown by desert-inhabiting species.
[12] Many examples of
convergent evolution have been identified in desert organisms, including between
cacti and
Euphorbia,
kangaroo rats and
jerboas,
Phrynosoma and
Moloch lizards.
Some flora includes shrubs,
Prickly Pears,
Desert Holly, and the
Brittlebush. Most desert
plants are drought- or salt-tolerant, such as
xerophytes. Some store water in their leaves, roots, and stems. Other desert plants have long
taproots that penetrate to the water table if present, or have adapted to the weather by having wide-spreading
roots to absorb water from a greater
area of the ground. Another adaptation is the development of small, spiny
leaves which shed less moisture than
deciduous leaves with greater surface areas. The stems and leaves of some plants lower the surface velocity of sand-carrying winds and protect the ground from erosion. Even small fungi and microscopic plant organisms found on the soil surface (so-called
cryptobiotic soil) can be a vital link in preventing erosion and providing support for other living organisms.
Deserts typically have a plant cover that is sparse but enormously diverse. The giant
saguaro cacti of the
Sonoran Desert provide nests for desert birds and serve as "trees" of the desert. Saguaro grow slowly but may live up to 200 years. When 9 years old, they are about 15 centimeters (6 in) high. After about 75 years, the cacti develop their first branches. When fully grown, saguaro cacti are 15 meters (50 ft) tall and weigh as much as 10 tons. They dot the Sonoran and reinforce the general impression of deserts as cactus-rich land.
Although
cacti are often thought of as characteristic desert plants, other types of plants have adapted well to the arid environment. They include the
pea and
sunflower families. Cold deserts have grasses and shrubs as dominant vegetation.
Atacama is the driest place on
Earth[13][14][15][16] and is virtually sterile because it is blocked from moisture on both sides by the Andes mountains and by the
Chilean Coast Range. The cold
Humboldt Current and the
anticyclone of the Pacific are essential to keep the dry climate of the Atacama. The average rainfall in the Chilean region of
Antofagasta is just 1 mm per year. Some weather stations in the Atacama have never received rain. Evidence suggests that the Atacama may not have had any significant rainfall from 1570 to 1971. It is so arid that mountains that reach as high as 6,885 meters (22,590 feet) are completely free of
glaciers and, in the southern part from 25°S to 27°S, may have been glacier-free throughout the
Quaternary, though
permafrost extends down to an altitude of 4,400 meters and is continuous above 5,600 meters.
Rain
does fall occasionally in deserts, and desert storms are often violent. A record 44 millimeters (1.7 in) of rain once fell within 3 hours in the Sahara. Large Saharan storms may deliver up to 1 millimeter per minute. Normally dry stream channels, called
arroyos or
wadis, can quickly fill after heavy rains, and
flash floods make these channels dangerous.
A flash flood in the Gobi
Though little rain falls in deserts, deserts receive runoff from ephemeral, or short-lived, streams fed considerable quantities of sediment for a day or two. Although most deserts are in basins with closed or interior drainage, a few deserts are crossed by 'exotic' rivers that derive their water from outside the desert. Such rivers infiltrate soils and evaporate large amounts of water on their journeys through the deserts, but their volumes are such that they maintain their continuity. The
Nile River, the
Colorado River, and the
Yellow River are exotic rivers that flow through deserts to deliver their sediments to the sea. Deserts may also have underground springs, rivers, or reservoirs that lie close to the surface, or deep underground. Plants that have not completely adapted to sporadic rainfalls in a desert environment may tap into underground water sources that do not exceed the reach of their root systems.
While deserts are well-known for their lack of water, some groups have adapted ways to find water in this harsh environment. The
Bedouin, for example, turn over half-buried stones just before dawn so dew forms on them.
[17]
Lakes form where rainfall or meltwater in interior drainage basins is sufficient. Desert lakes are generally shallow, temporary, and salty. Because these lakes are shallow and have a low bottom gradient, wind stress may cause the lake waters to move over many square kilometers. When small lakes dry up, they leave a salt crust or
hardpan. The flat area of clay, silt, or sand encrusted with salt that forms is known as a
playa or a sink. There are more than a hundred playas in North American deserts. Most are relics of large lakes that existed during the last
ice age about 12,000 years ago.
Lake Bonneville was a 52,000-square-kilometer (20,000 mi²) lake almost 300 meters (1000 ft) deep in Utah, Nevada, and Idaho during the Ice Age. Today the remnants of Lake Bonneville include Utah's
Great Salt Lake,
Utah Lake, and
Sevier Lake. Because playas are arid landforms from a wetter past, they contain useful clues to climatic change.
When the occasional precipitation does occur, it erodes the desert rocks quickly.
The flat terrains of hardpans and playas make them excellent racetracks and natural runways for airplanes and spacecraft. Ground-vehicle speed records have been established on the flat lakebeds of the
Black Rock Desert in Nevada and
Bonneville Speedway in Utah. Space shuttles and flight-test aircraft land on Rogers Lake Playa at
Edwards Air Force Base in California.
[edit] Formation of hot deserts
There are four main, interlinked causes of hot deserts:
[citation needed]
- The formation of the subtropical high-pressure cell.
- The rain shadow effect in the belt of easterly trade winds.
- The effect of the cold currents off the west coast of the continents at these latitudes.
- The depositing sands of a desert along its border into the fertile land
It must be noted that also hot deserts (like cold deserts) may result in average temperature cooling
[18] because they reflect more of the incoming light (their
albedo is higher than that of water or forests).
[edit] Mineral resources
Deserts may contain great amounts of mineral resources over their entire surface. This occurrence in minerals also determines the color. For example, the red color of many sand deserts is a result of the occurrence of
laterite.
[19]
Some
mineral deposits are formed, improved, or preserved by geologic processes that occur in arid lands as a consequence of climate.
Ground water leaches ore minerals and redeposits them in zones near the
water table. This leaching process concentrates these minerals as ore that can be mined.
Evaporation in arid lands enriches mineral accumulation in their lakes. Lake beds known as
playas may be sources of mineral deposits formed by evaporation. Water evaporating in closed basins precipitates minerals such as
gypsum, salts (including
sodium nitrate and
sodium chloride), and
borates. The minerals formed in these
evaporite deposits depend on the composition and temperature of the saline waters at the time of deposition.
Significant evaporite resources occur in the
Great Basin Desert of the United States, mineral deposits made famous by the "20-mule teams" that once hauled borax-laden wagons from
Death Valley to the
railroad.
Boron, from
borax and borate evaporites, is an essential ingredient in the manufacture of glass, enamel, agricultural chemicals, water softeners, and pharmaceuticals. Borates are mined from evaporite deposits at
Searles Lake, California, and other desert locations. The total value of chemicals that have been produced from Searles Lake substantially exceeds
US$1
billion.
The
Atacama Desert of
Chile is unique among the deserts of the world in its great abundance of saline minerals. Sodium nitrate has been mined for
explosives and
fertilizer in the Atacama since the middle of the 19th century. Nearly 3 million
metric tons were mined during
World War I.
Valuable minerals located in arid lands include
copper in the United States, Chile,
Peru, and
Iran;
iron and
lead-
zinc ore in
Australia; and
gold,
silver, and
uranium deposits in Australia and the United States. Nonmetallic mineral resources and rocks such as
beryllium,
mica,
lithium,
clays,
pumice, and
scoria also occur in arid regions.
Sodium carbonate,
sulfate, borate,
nitrate, lithium,
bromine,
iodine,
calcium, and
strontium compounds come from sediments and near-surface brines formed by evaporation of inland bodies of water, often during geologically recent times.
The
Green River Formation of
Colorado,
Wyoming, and
Utah contains
alluvial fan deposits and playa evaporites created in a huge lake whose level fluctuated for millions of years. Economically significant deposits of
trona, a major source of
sodium compounds, and thick layers of
oil shale were created in the arid environment.
Some of the more productive
petroleum areas on Earth are found in arid and semiarid regions of Africa and the Mideast, although the
oil fields were originally formed in shallow marine environments. Recent climate change has placed these reservoirs in an arid environment. It's noteworthy that
Ghawar, the world's largest and most productive oilfield is mostly under the
Empty Quarter and
Al-Dahna deserts.
Other oil reservoirs, however, are presumed to be
eolian in origin and are presently found in humid environments. The
Rotliegendes, a
hydrocarbon reservoir in the
North Sea, is associated with extensive evaporite deposits. Many of the major U.S. hydrocarbon resources may come from eolian sands. Ancient
alluvial fan sequences may also be hydrocarbon reservoirs.
[edit] Solar energy resources
Deserts are increasingly seen as sources for
solar energy. The
Negev Desert and the surrounding area, including the
Arava Valley, are the sunniest parts of Israel and little of this land is
arable, which is why it has become the center of the
Israeli solar industry.
[20] David Faiman, a world expert on solar energy, feels the energy needs of a country like
Israel could be met by building solar energy plants in the Negev.
[21] Faiman also feels the technology now exists to supply all of the world's electricity needs with 10 percent of the
Sahara.
[21] Solel has nine fields of solar collectors in the
Mojave Desert of California.
[22] It recently signed a contract to build the
Mojave Solar Park, which will be the world's largest solar generating plant.
[23][24]
[edit] Human life in deserts
Mahktesh Gadol, an erosional basin in the
Negev Desert of southern Israel
A desert is a hostile, potentially deadly environment for unprepared humans. In hot deserts, high temperatures cause rapid loss of water due to
sweating, and the absence of water sources with which to replenish it can result in
dehydration and death within a few days. In addition, unprotected humans are also at risk from
heatstroke.
Humans may also have to adapt to
sandstorms in some deserts, not just in their adverse effects on
respiratory systems and eyes, but also in their potentially harmful effects on equipment such as
filters, vehicles and communication equipment. Sandstorms can last for hours, sometimes even days. This makes surviving in the desert quite difficult for humans.
Despite this, some cultures have made hot deserts their home for thousands of years, including the
Bedouin,
Tuareg and
Pueblo people. Modern technology, including advanced
irrigation systems,
desalinization and
air conditioning have made deserts much more hospitable. In the
United States and
Australia for example,
desert farming has found extensive use.
In cold deserts,
hypothermia and
frostbite are the chief hazards, as well as
dehydration in the absence of a source of heat to melt ice for drinking. Falling through pack-ice or surface ice layers into freezing water is a particular danger requiring emergency action to prevent rapid hypothermia. Starvation is also a hazard; in low temperatures the body requires much more
food energy to maintain body heat and to move. As with hot deserts, some people such as the
Inuit have adapted to the harsh conditions of cold deserts.
Most traditional human life in deserts is
nomadic. It depends in hot deserts on finding water, and on following infrequent rains to obtain grazing for livestock. In cold deserts, it depends on finding good hunting and fishing grounds, on sheltering from blizzards and winter extremes, and on storing enough food for winter. Permanent settlement in both kinds of deserts requires permanent water and food sources and adequate shelter, or the technology and energy sources to provide it.
Many deserts are flat and featureless, lacking landmarks, or composed of repeating landforms such as sand dunes or the jumbled ice-fields of glaciers. Advanced skills or devices are required to navigate through such landscapes and inexperienced travellers may perish when supplies run out after becoming lost. In addition sandstorms or
blizzards may cause disorientation in severely reduced visibility.
The danger represented by wild animals in deserts has been featured in explorers' accounts but does not cause higher rates of death than in other environments such as rain forests or savanna woodland, and generally does not by itself affect human distribution. Defense against
polar bears may be advisable in some areas of the Arctic, as may precautions against
venomous snakes and
scorpions in choosing sites at which to
camp in some hot deserts.
[edit] See also
[edit] References
- ^ a b c d "What is a desert?". Pubs.usgs.gov. http://pubs.usgs.gov/gip/deserts/what/. Retrieved 2010-10-16.
- ^ According to What is a desert?, the 250 mm threshold definition is attributed to Peveril Meigs.
- ^ "desert". Encyclopædia Britannica online. http://www.britannica.com/eb/article-70815/desert. Retrieved 2008-02-09.
- ^ Fredlund, D.G.; Rahardjo, H. (1993) (PDF). Soil Mechanics for Unsaturated Soils. Wiley-Interscience. ISBN 978-0471850083. http://www.soilvision.com/subdomains/unsaturatedsoil.com/Docs/chapter1UST.pdf. Retrieved 2008-05-21.
- ^ Glossary of Meteorology. Megathermal Climate. Retrieved on 2008-05-21.
- ^ 1911 Encyclopedia Britannica
- ^ Heinrich Walter; Siegmar-W. Breckle (2002). Walter's Vegetation of the earth: the ecological systems of the geo-biosphere. Springer. pp. 457–. ISBN 9783540433156. http://books.google.com/?id=SdaCSwxK5bIC&pg=PA457. Retrieved 24 July 2010.
- ^ S.S. Negi (1 March 2002). Cold Deserts of India. Indus Publishing. pp. 9–. ISBN 9788173871276. http://books.google.com/?id=54RgJ6FgMl0C&pg=PA9. Retrieved 24 July 2010.
- ^ Robert V. Rohli; Anthony J. Vega (2008). Climatology. Jones & Bartlett Learning. pp. 207–. ISBN 9780763738280. http://books.google.com/?id=Zhbqbrg2XswC&pg=PA207. Retrieved 25 July 2010.
- ^ David Neville Thomas; Gordon Elliott Fogg; P. Convey; C.H. Fritsen, J.-M. Gili (2008). The biology of polar regions. Oxford University Press. pp. 64–. ISBN 9780199298136. http://books.google.com/?id=-ErSVcvhI4oC&pg=PA64. Retrieved 24 July 2010.
- ^ W. Berry Lyons; C. Howard-Williams; Ian Hawes (1997). Ecosystem processes in Antarctic ice-free landscapes: proceedings of an International Workshop on Polar Desert Ecosystems : Christchurch, New Zealand, 1–4 July 1996. Taylor & Francis. pp. 3–. ISBN 9789054109259. http://books.google.com/?id=VKtCnLa5uaYC&pg=PA3. Retrieved 25 July 2010.
- ^ Al-kahtani, M.A.; C. Zuleta, E. Caviedes-Vidal, and T. Garland, Jr. (2004). "Kidney mass and relative medullary thickness of rodents in relation to habitat, body size, and phylogeny". Physiological and Biochemical Zoology 77 (3): 346–365. doi:10.1086/420941. PMID 15286910. http://www.biology.ucr.edu/people/faculty/Garland/Al-kahtaniEA2004.pdf.
- ^ a b "Nationalgeographic.com". Ngm.nationalgeographic.com. http://ngm.nationalgeographic.com/ngm/0308/feature3/. Retrieved 2010-10-16.
- ^ "Extremescience.com". Extremescience.com. http://www.extremescience.com/DriestPlace.htm. Retrieved 2010-10-16.
- ^ "NASA.gov" (PDF). http://quest.nasa.gov/challenges/marsanalog/egypt/AtacamaAdAstra.pdf. Retrieved 2010-10-16.
- ^ Boehm, Richard G.; Editors and writers of The World and Its People (2006). The World and Its People (2005 ed.). Columbus, Ohio: Glencoe. p. 276. ISBN 0-07-860977-1.
- ^ "PBS.org". PBS.org. http://www.pbs.org/lawrenceofarabia/revolt/water.html. Retrieved 2010-10-16.
- ^ "Celsias.com". Celsias.com. 2008-12-26. http://www.celsias.com/article/all-about-albedo-lighter-world-cooler-world/. Retrieved 2010-10-16.
- ^ Tsjaad by Dorrit van Dalen
- ^ Head of Kibbutz Movement: We will not be discriminated against by the government, Ehud Zion Waldoks, Jerusalem Post, March 10, 2008.
- ^ a b Giant solar plants in Negev could power Israel's future, John Lettice, The Register, January 25, 2008
- ^ "Israel21c.org". Israel21c.org. 2007-07-26. http://www.israel21c.org/bin/en.jsp?enDispWho=Articles^l1721&enPage=BlankPage&enDisplay=view&enDispWhat=object&enVersion=0&enZone=Technology. Retrieved 2010-10-16.
- ^ Looking to the sun, Tom Parry, Canadian Broadcasting Corporation, August 15, 2007.
- ^ Sandler, Neal (2006-02-14). "Businessweek.com". Businessweek.com. http://www.businessweek.com/technology/content/feb2006/tc20060214_533101.htm. Retrieved 2010-10-16
