[131] Antoine de Saint-Exupéry described both his flying and the desert in Wind, Sand and Stars[132] and Gertrude Bell travelled extensively in the Arabian desert in the early part of the 20th century, becoming an expert on the subject, writing books and advising the British government on dealing with the Arabs. Desert environments are so dry that they support only extremely sparse vegetation; trees are usually absent and, under normal climatic conditions, shrubs or herbaceous plants provide only very incomplete ground cover. Competitive interactions are weak. A dune is a landform composed of wind- or water-driven sand.It typically takes the form of a mound, ridge, or hill. They occur in Namibia, Chile, southern California and Baja California. According to some definitions, any environment that is almost completely free of plants is considered desert, including regions too cold to support vegetation—i.e., “frigid deserts.” Other definitions use the term to apply only to hot and temperate deserts, a restriction followed in this account. As the desert dries out, the adult toads rebury themselves. [55] The Tassili Plateau in Algeria is an impressive jumble of eroded sandstone outcrops, canyons, blocks, pinnacles, fissures, slabs and ravines. Welcome to the Desert of the Real is a 2002 book by Slavoj Žižek.A Marxist and Lacanian analysis of the ideological and political responses to the terrorist attacks on September 11, 2001, Zizek's study incorporates various psychoanalytic, postmodernist, biopolitical, and (Christian) universalist influences into a Marxist dialectical framework. Polar deserts (also seen as "cold deserts") have similar features, except the main form of precipitation is snow rather than rain. Some animals remain in a state of dormancy for long periods, ready to become active again during the rare rainfall. [72], Some desert plants produce seed which lies dormant in the soil until sparked into growth by rainfall. When these are extensive, they are known as sand seas or ergs. Please refer to the appropriate style manual or other sources if you have any questions. [47], A sand sheet is a near-level, firm expanse of partially consolidated particles in a layer that varies from a few centimeters to a few meters thick. [63][64] Nevertheless, there is some plant life in the Atacama, in the form of specialist plants that obtain moisture from dew and the fogs that blow in from the Pacific. Other deserts are flat, stony plains where all the fine material has been blown away and the surface consists of a mosaic of smooth stones. They travelled over large areas with their herds, moving to new pastures as seasonal and erratic rainfall encouraged new plant growth. [47], Deserts and semi-deserts are home to ecosystems with low or very low biomass and primary productivity in arid or semi-arid climates. [2] Phrases such as "desert island"[3] and "Great American Desert", or Shakespeare's "deserts of Bohemia" (The Winter's Tale) in previous centuries did not necessarily imply sand or aridity; their focus was the sparse population. Not only do they require food and water but they also need to keep their body temperature at a tolerable level. A mirage is a naturally occurring optical phenomenon in which light rays bend via refraction to produce a displaced image of distant objects or the sky. The Sahara Desert also has the empty space totalling hundreds of square miles required to house fields of mirrors for solar plants. [104], People have been living in deserts for millennia. [89] Jerboas, desert rats, kangaroo rats and other small rodents emerge from their burrows at night and so do the foxes, coyotes, jackals and snakes that prey on them. Items found in most deserts: Dunes , Erg , Oasis and Barchan Definition . [30] During the day the sky is usually clear and most of the sun's radiation reaches the ground, but as soon as the sun sets, the desert cools quickly by radiating heat into space. Further inland, areas receive very little precipitation. The mean particle size was 1.44 μm. In areas that have … / I have it in me so much nearer home / To scare myself with my own desert places. As a steady wind begins to blow, fine particles lying on the exposed ground begin to vibrate. [8] [122] Desertec Industrial Initiative was a consortium seeking $560 billion to invest in North African solar and wind installations over the next forty years to supply electricity to Europe via cable lines running under the Mediterranean Sea. And place upon him rough and jagged rocks, and cover him with darkness, and let him abide there for ever, and cover his face that he may not see light. [112] Geological processes in a desert climate can concentrate minerals into valuable deposits. [88] Carnivores can obtain much of their water needs from the body fluids of their prey. Evapotranspiration is the combination of water loss through atmospheric evaporation and through the life processes of plants. [37] In a really severe steady blow, 2 m (6 ft 7 in) is about as high as the sand stream can rise as the largest sand grains do not become airborne at all. [50] Dunes are sometimes solitary, but they are more often grouped together in dune fields. Sand dunes in the Sahara, near Merzouga, Morocco. [38] The electric fields are caused by the collision between airborne particles and by the impacts of saltating sand grains landing on the ground. Bottomlands may be salt-covered flats. The High Desert at sunset in Johnson Valley, along CA State Route 247. [76], Animals adapted to live in deserts are called xerocoles. [72] The giant saguaro cacti of the Sonoran Desert form "forests", providing shade for other plants and nesting places for desert birds. A desert is a geographical region that receives little rain. This is believed to be caused by the stresses put on the rock by repeated thermal expansions and contractions which induces fracturing parallel to the original surface. The sandgrouse is an expert at this and nests on the open desert floor dozens of kilometers (miles) away from the waterhole it needs to visit daily. Wells are dug to extract water from the porous sandstone that lies underneath. In deserts, trees are usually absent, and shrubs or herbaceous plants provide only very incomplete ground cover. But more than that, she's interested in the way things that are near each other are similar. Here, rivers, such as the Colorado, have cut their way over the millennia through the high desert floor, creating canyons that are over a mile (6,000 feet or 1,800 meters) deep in places, exposing strata that are over two billion years old. Tanks and armoured vehicles were able to travel large distances unimpeded and land mines were laid in large numbers. Potential evapotranspiration, then, is the amount of water that could evaporate in any given region. The lack of vegetation exposes the unprotected surface of the ground to the processes of denudation. [30], As the desert mountains decay, large areas of shattered rock and rubble occur. [103] David Faiman has proposed that "giant" solar plants in the Negev could supply all of Israel's needs for electricity. They usually receive precipitation from 250 mm (10 in) to 500 mm (20 in) but this can vary due to evapotranspiration and soil nutrition. [11] Polar deserts cover much of the ice-free areas of the Arctic and Antarctic. The upwind slope typically has a gradient of 10° to 20° while the lee slope is around 32°, the angle at which loose dry sand will slip. This migration is reflected in close floristic similarities currently observed in these places. When the lakes dry up, they leave a crust or hardpan behind. In fact, with a very few exceptions, their basal metabolic rate is determined by body size, irrespective of the climate in which they live. Orographic lift occurs as air masses rise to pass over high ground. This may have happened when drought caused the death of herd animals, forcing herdsmen to turn to cultivation. [72], Cacti are present in both North and South America with a post-Gondwana origin. [5] Deserts generally receive less than 250 mm (10 in) of precipitation each year. For perennial plants, reproduction is more likely to be successful if the seed germinates in a shaded position, but not so close to the parent plant as to be in competition with it. Some major oilfields such as Ghawar are found under the sands of Saudi Arabia. [66] Seepages may occur in the walls of canyons and pools may survive in deep shade near the dried up watercourse below. He soon discovered that the white drops on the shrub’s stems were the digestive byproduct of insects that feed on the plant’s sap, known as honeydew. About one-third of the land surface of the world is arid or semi-arid. Aziz Ali Dad. [83][85] Herbivorous mammals obtain moisture from the plants they eat. The Sahara Desert is of this type. Plants and animals living in the desert need special adaptations to survive in the harsh environment. These larger particles anchor the other particles in place and may also be packed together on the surface so as to form a miniature desert pavement. When there are two directions from which winds regularly blow, a series of long, linear dunes known as seif dunes may form. [8], Deserts are also classified, according to their geographical location and dominant weather pattern, as trade wind, mid-latitude, rain shadow, coastal, monsoon, or polar deserts. [102] Evaporites are found in the USA's Great Basin Desert, historically exploited by the "20-mule teams" pulling carts of borax from Death Valley to the nearest railway. Once fertility has been built up, further crop production preserves the soil from destruction by wind and other forms of erosion. The sand streams along above the surface of the ground like a fluid, often rising to heights of about 30 cm (12 in). [105], The desert nomads were also traders. Rounded mounds of sand without a slip face are the rare dome dunes, found on the upwind edges of sand seas. They represent the most extreme result of the progressive cooling and consequent aridification of global climates during the Cenozoic Era (65.5 million years ago to the present), which also led to the development of savannas and scrublands in the less arid regions near the tropical and temperate margins of the developing deserts. By knowing back routes and the locations of oases and by utilizing camels, Muslim Arab forces were able to successfully overcome both Roman and Persian forces in the period 600 to 700 AD during the expansion of the Islamic caliphate. Few make it to adulthood. This is because they reflect more of the incoming light and their albedo is higher than that of forests or the sea. 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 even evaporate ice. Migration between discrete desert regions also has been relatively easier for those plants adapted to survival in saline soils because such conditions occur not only in deserts but also in coastal habitats. In addition, many kinds of desert-adapted wildlife will seek water and also take shelter from the blazing sun in local oases. Some plants have resolved this problem by adopting crassulacean acid metabolism, allowing them to open their stomata during the night to allow CO2 to enter, and close them during the day,[70] or by using C4 carbon fixation. Desert fever: A disease also called coccidioidomycosis (CM) due to a fungus called Coccidioides immitis. It minimizes its water loss by producing concentrated urine and dry dung, and is able to lose 40% of its body weight through water loss without dying of dehydration. It seems probable that with the onset of virtual life, the orientation of people and the very definition of ‘human’ will transform. As an example, Tucson, Arizona receives about 300 mm (12 in) of rain per year, however about 2,500 mm (98 in) of water could evaporate over the course of a year. In hot deserts, gliding birds can remove themselves from the over-heated desert floor by using thermals to soar in the cooler air at great heights. These regions feature a semi-arid climate and are less extreme than regular deserts. By signing up for this email, you are agreeing to news, offers, and information from Encyclopaedia Britannica. When rain falls, the water is rapidly absorbed by the shallow roots and retained to allow them to survive until the next downpour, which may be months or years away. [26], Polar deserts such as McMurdo Dry Valleys remain ice-free because of the dry katabatic winds that flow downhill from the surrounding mountains. Resources are often ephemeral or episodic, and this triggers sporadic animal movements and ‘pulse and reserve’ or ‘boom-bust’ ecosystem dynamics. [48] Small ripples form on the sand sheet when the wind exceeds 24 km/h (15 mph). Other areas are arid by virtue of being a very long way from the nearest available sources of moisture. Opening stomata to allow in the carbon dioxide necessary for the process causes evapotranspiration, and conservation of water is a top priority for desert vegetation. [32] Exfoliation also occurs when the outer surfaces of rocks split off in flat flakes. [8] For example, Phoenix, Arizona, receives less than 250 mm (9.8 in) of precipitation per year, and is immediately recognized as being located in a desert because of its aridity-adapted plants. However, this would have been primarily before the evolution of angiosperms (flowering plants, the group to which most present-day plants, including those of deserts, belong). While there they shed their skins a number of times and retain the remnants around them as a waterproof cocoon to retain moisture. Vegetation plays a major role in determining the composition of the soil. [17], Cold deserts, sometimes known as temperate deserts, occur at higher latitudes than hot deserts, and the aridity is caused by the dryness of the air. While present day desert cities like Las Vegas, 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. The word comes to English via the French (se) mirer, from the Latin mirari, meaning "to look at, to wonder at".. Mirages can be categorized as "inferior" (meaning lower), "superior" (meaning higher) and "Fata Morgana", one kind of superior mirage consisting of a … Montane deserts are normally cold, or may be scorchingly hot by day and very cold by night as is true of the northeastern slopes of Mount Kilimanjaro. Let us know if you have suggestions to improve this article (requires login). Please select which sections you would like to print: While every effort has been made to follow citation style rules, there may be some discrepancies. Many, such as the Bushmen in the Kalahari, the Aborigines in Australia and various tribes of North American Indians, were originally hunter-gatherers. For arid climate, see, Area of land where little precipitation occurs, International Center for Agricultural Research in the Dry Areas, "How mountains influence rainfall patterns", "CHAPTER 8: Introduction to the Hydrosphere (e) Cloud Formation Processes", "The formation of fine particles in sandy deserts and the nature of 'desert' loess", 10.1306/74d71a69-2b21-11d7-8648000102c1865d, "Physics, Mechanics and Processes of Dust and Sandstorms", "Retrieval of mass and sizes of particles in sandstorms using two MODIS IR bands: A case study of April 7, 2001 sandstorm in China", 10.1175/1520-0450(1969)008<0032:GCODD>2.0.CO;2, "The electrification of snowstorms and sandstorms", "Misconceptions surround desert terrain, vegetation", "Desert varnish: evidence for cyclic deposition of manganese", "Geology of Grand Canyon National Park, North Rim", "Even the Driest Place on Earth Has Water", "Two dry for life: the Atacama Desert and Mars", "Too dry for life: The Atacama Desert and Mars", "Colonel Qaddafi and the Great Man-made River", "Nature's green revolution: the remarkable evolutionary rise of C4 plants", "How Plants Cope with the Desert Climate", "Adaptation to cold in arctic and tropical mammals and birds in relation to body temperature, insulation, and basal metabolic rate", "Kidney mass and relative medullary thickness of rodents in relation to habitat, body size, and phylogeny", "A method for the calculation of metabolic water", "What secrets lie within the camel's hump? [31], Such large temperature variations have a destructive effect on the exposed rocky surfaces. The Thar Desert, also known as the Great Indian Desert, is a large, arid region in the northwestern part of the Indian subcontinent that covers an area of 200,000 km 2 (77,000 sq mi) and forms a natural boundary between India and Pakistan.It is the world's 17th-largest desert, and the world's 9th-largest hot subtropical desert.. About 85% of the Thar Desert is located within India, and the remaining 15% is in … [40], Sandstorms occur with much less frequency than dust storms. [122], The Arabs were probably the first organized force to conduct successful battles in the desert. [36], Sand and dust storms are natural events that occur in arid regions where the land is not protected by a covering of vegetation. Temporary lakes may form and salt pans may be left when waters evaporate. Like other desert birds, it is well-camouflaged by its coloring and can merge into the landscape when stationary. Lizards and snakes are the most numerous in arid regions and certain snakes have developed a novel method of locomotion that enables them to move sidewards and navigate high sand-dunes. The desert of the real . Welwitschia has only two leaves, which are leathery, straplike organs that emanate from the middle of a massive, mainly subterranean woody stem. How to use barren in a sentence. something, as a period of history, phase of existence, or locality, that is spiritually or intellectually barren. [24] They include the Tengger and Sonoran Deserts. In the process they cool and lose much of their moisture by precipitation on the windward slope of the mountain range. The arctic weasel has a metabolic rate that is two or three times as high as would be expected for an animal of its size. Desertification is a type of land degradation in drylands in which biological productivity is lost due to natural processes or induced by human activities whereby fertile areas become increasingly arid. [128], The desert is generally thought of as a barren and empty landscape. [102], Oil and gas form on the bottom of shallow seas when micro-organisms decompose under anoxic conditions and later become covered with sediment. [91], Being ectotherms, reptiles are unable to live in cold deserts but are well-suited to hot ones. A dessert is the sweet course at the end of a meal. Both extremely arid and arid lands are considered to be deserts while semiarid lands are generally referred to as steppes when they are grasslands. [47] A hamada is a type of desert landscape consisting of a high rocky plateau where the sand has been removed by aeolian processes. About one-third of the land surface of the world is arid or semi-arid. Deserts can be classified by the amount of precipitation that falls, by the temperature that prevails, by the causes of desertification or by their geographical location. These leaves grow perpetually from their bases and erode progressively at their ends. There may be underground sources of water, in the form of springs and seepages from aquifers. [116], A modern example of desert farming is the Imperial Valley in California, which has high temperatures and average rainfall of just 3 in (76 mm) per year.
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