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The cold Humboldt Current and the anticyclone of the Pacific are essential to keep the dry climate of the Atacama. Once ejected, these particles move in one of three possible ways, depending on their size, shape and density; suspension, saltation or creep. The ripples are ephemeral and a change in wind direction causes them to reorganise. Wind-blown sand grains striking any solid object in their path can abrade the surface. [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. [68] These include the Great Salt Lake, Utah Lake, Sevier Lake and many dry lake beds. [8] Animals need to keep cool and find enough food and water to survive. At greater wind speeds, some particles are lifted into the air stream. [9] Other regions of the world have cold deserts, including areas of the Himalayas[10] and other high-altitude areas in other parts of the world. Eolian processes are major factors in shaping desert landscapes. [17][18] Arid deserts receive between 25 and 200 mm (1 and 8 in) in a year and semiarid deserts between 200 and 500 mm (8 and 20 in). 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. Deserts have strong temporal variability in the availability of resources due to the total amount of annual rainfall and the size of individual rainfall events. The average precipitation in the Chilean region of Antofagasta is just 1 mm (0.039 in) per year. Many mean annual temperatures range from 20-25° C. The extreme maximum ranges from 43.5-49° C. Minimum temperatures sometim… Daily variations in temperature can be as great as 22 °C (40 °F) or more, with heat loss by radiation at night being increased by the clear skies. The range of temperatures on a daily and annual scale is relatively low, being 11 °C (20 °F) and 5 °C (9 °F) respectively in the Atacama Desert. Our editors will review what you’ve submitted and determine whether to revise the article. Get a Britannica Premium subscription and gain access to exclusive content. This exposes coarser-grained material, mainly pebbles with some larger stones or cobbles,[36][47] leaving a desert pavement, an area of land overlaid by closely packed smooth stones forming a tessellated mosaic. Nomads have moved their flocks and herds to wherever grazing is available, and oases have provided opportunities for a more settled way of life. Most deserts are in basins with no drainage to the sea but some are crossed by exotic rivers sourced in mountain ranges or other high rainfall areas beyond their borders. Both extremely arid and arid lands are considered to be deserts while semiarid lands are generally referred to as steppes when they are grasslands. 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. Welwitschia has only two leaves, which are leathery, straplike organs that emanate from the middle of a massive, mainly subterranean woody stem. Rates of evapotranspiration in cold regions such as Alaska are much lower because of the lack of heat to aid in the evaporation process. Half a million Americans were forced to leave their land in this catastrophe. A semi-arid desert or a steppe is a version of the arid desert with much more rainfall, vegetation and higher humidity. [128], The desert is generally thought of as a barren and empty landscape. Photosynthesis is the key to plant growth. This migration is reflected in close floristic similarities currently observed in these places. [47] Where sand does occur, it is usually in large quantities in the form of sand sheets or extensive areas of dunes. These areas are known as desert pavements, and little further erosion takes place. Temperatures exhibit daily extremes because the atmosphere contains little humidity to block the Sun's rays. [5] Deserts generally receive less than 250 mm (10 in) of precipitation each year. An area with dunes is called a dune system or a dune complex. Such electric fields, which range in size up to 80 kV/m, can produce sparks and cause interference with telecommunications equipment. Desert, any large, extremely dry area of land with sparse vegetation. [4], A desert is a region of land that is very dry because it receives low amounts of precipitation (usually in the form of rain, but it may be snow, mist or fog), often has little coverage by plants, and in which streams dry up unless they are supplied by water from outside the area. [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. This is due in part to intrinsic physiologic characteristics in some widespread desert families that preadapt the plants to an arid environment; it also is a result of plant migration occurring through chance seed dispersal among desert regions. [102], Oil and gas form on the bottom of shallow seas when micro-organisms decompose under anoxic conditions and later become covered with sediment. Only a few primitive plants, which may have been part of the ancient desert vegetation, occur in present-day deserts. This area of deposited clay, silt or sand is known as a playa. [30], As the desert mountains decay, large areas of shattered rock and rubble occur. [57], One of the driest places on Earth is the Atacama Desert. The description of manna in the Bible matches what Danin found in the Sinai Desert. [52], A large part of the surface area of the world's deserts consists of flat, stone-covered plains dominated by wind erosion. Wells are dug to extract water from the porous sandstone that lies underneath. [37] Denser clouds of dust can be formed in stronger winds, moving across the land with a billowing leading edge. Cold deserts often have high concentrations of salt in the soil. Montane definition is - of, relating to, growing in, or being the biogeographic zone of relatively moist cool upland slopes below timberline dominated by large coniferous trees. Many desert reptiles are ambush predators and often bury themselves in the sand, waiting for prey to come within range. The process continues and the end products are either dust or sand. A desert is a barren area of landscape where little precipitation occurs and, consequently, living conditions are hostile for plant and animal life. [71], Many desert plants have reduced the size of their leaves or abandoned them altogether. [35] The sand eventually ends up deposited in level areas known as sand-fields or sand-seas, or piled up in dunes. In order to conserve energy, other desert birds run rather than fly. [44], Many people think of deserts as consisting of extensive areas of billowing sand dunes because that is the way they are often depicted on TV and in films,[45] but deserts do not always look like this. Many, such as the Bushmen in the Kalahari, the Aborigines in Australia and various tribes of North American Indians, were originally hunter-gatherers. Large numbers of slaves were also taken northwards across the Sahara. [58], When rain falls in deserts, as it occasionally does, it is often with great violence. Real definition of desert 2 See answers sarveshcpr sarveshcpr Explanation: In geography, a desert is a landscape form or region that receives very little precipitation. 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. Eggs are laid and the tadpoles grow rapidly as they must reach metamorphosis before the water evaporates. [83] The kangaroo rat for example makes use of this water of metabolism and conserves water both by having a low basal metabolic rate and by remaining underground during the heat of the day,[84] reducing loss of water through its skin and respiratory system when at rest. They share some characteristics of a true desert and are usually located at the edge of deserts and continental dry areas. [107] Traditional means of overland transport declined with the advent of motor vehicles, shipping and air freight, but caravans still travel along routes between Agadez and Bilma and between Timbuktu and Taoudenni carrying salt from the interior to desert-edge communities. Others store water in succulent leaves or stems or in fleshy tubers. [11] Polar deserts cover much of the ice-free areas of the Arctic and Antarctic. However, such factors as the temperature, humidity, rate of evaporation and evapotranspiration, and the moisture storage capacity of the ground have a marked effect on the degree of aridity and the plant and animal life that can be sustained. [103] David Faiman has proposed that "giant" solar plants in the Negev could supply all of Israel's needs for electricity. The juveniles stay on the surface for a while, feeding and growing, but soon dig themselves burrows. Definition of dessert 1 : a usually sweet course or dish (as of pastry or ice cream) usually served at the end of a meal 2 British : a fresh fruit served after a sweet course The Tuareg were traders and the goods transported traditionally included slaves, ivory and gold going northwards and salt going southwards. Generally deserts are defined as areas that receive an average annual precipitation of less than 250 mm (10 inches). [76], Animals adapted to live in deserts are called xerocoles. In addition, many kinds of desert-adapted wildlife will seek water and also take shelter from the blazing sun in local oases. Corrections? Let us know if you have suggestions to improve this article (requires login). [28][29], Deserts usually have a large diurnal and seasonal temperature range, with high daytime temperatures falling sharply at night. 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 … 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. Others, such as brine shrimps, fairy shrimps and tadpole shrimps, are cryptobiotic and can lose up to 92% of their bodyweight, rehydrating as soon as it rains and their temporary pools reappear. [91], Being ectotherms, reptiles are unable to live in cold deserts but are well-suited to hot ones. [77] The emperor penguin has dense plumage, a downy under layer, an air insulation layer next to the skin and various thermoregulatory strategies to maintain its body temperature in one of the harshest environments on Earth. 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 North Slope of Alaska's Brooks Range also receives less than 250 mm (9.8 in) of precipitation per year and is often classified as a cold desert. These types of dune are rare, and only form in closed arid basins that retain the highly soluble gypsum that would otherwise be washed into the sea. It is the hottest desert in the North American continent with air temperatures consistently rising above 118°F (48°C). The sweet liquid hardens to the form of white granules and is still collected from spring to early fall in many … 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. While there’s no one standard definition to go by, food deserts are generally considered to be places where residents don’t have access to affordable nutritious foods like fruits, vegetables, and whole grains. mirage and Vision Synonym Discussion of mirage. [114], The Judean Desert was farmed in the 7th century BC during the Iron Age to supply food for desert forts. [83][85] Herbivorous mammals obtain moisture from the plants they eat. They occur in Namibia, Chile, southern California and Baja California. [72] The stems and leaves of some plants lower the surface velocity of sand-carrying winds and protect the ground from erosion. a census tract-level definition of food deserts—areas with limited access to affordable and healthy food—to the contiguous United States using 2000 Census data. Their self-sufficient skills and knowledge were passed down through the generations by word of mouth. Real-time strategy games are often compared to turn-based strategy games, where each player has time to carefully consider the next move without having to worry about the actions of his opponent. Transverse dunes run at a right angle to the prevailing wind direction. [74][75] In common with cacti, many have developed spines to ward off browsing animals. The grasses that held the soil in place were ploughed under, and a series of dry years caused crop failures, while enormous dust storms blew the topsoil away. In a dust storm, these fine particles are lifted up and wafted aloft to heights of up to 6 km (3.7 mi). [14] The characteristics of hot deserts include high temperatures in summer; greater evaporation than precipitation, usually exacerbated by high temperatures, strong winds and lack of cloud cover; considerable variation in the occurrence of precipitation, its intensity and distribution; and low humidity. Erosion and sedimentation are high due to the sparse vegetation cover and the activities of large mammals and people. 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 Turks were defeated by the British, who had the backing of irregular Arab forces that were seeking to revolt against the Turks in the Hejaz, made famous in T.E. In areas that have … 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. [139] The surface of Titan, a moon of Saturn, also has a desert-like surface with dune seas. The smaller dune fields occupy the bottom of many of the craters situated in the Martian polar regions. They are mostly in areas remote from the sea where most of the moisture has already precipitated from the prevailing winds. And again the Lord said to Raphael: 'Bind Azazel hand and foot, and cast him into the darkness: and make an opening in the desert, which is in Dudael, and cast him therein. The victors in a battle would advance and their supply chain would necessarily become longer, while the defeated army could retreat, regroup and resupply. [109], Similar damage is being done today to the semi-arid areas that rim deserts and about twelve million hectares of land are being turned to desert each year. 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. [1] 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. Deserts of this type are often long and narrow and bounded to the east by mountain ranges. As this wind-induced movement of sand grains takes place, the dune moves slowly across the surface of the ground. Saguaro grows slowly but may live for up to two hundred years. As a steady wind begins to blow, fine particles lying on the exposed ground begin to vibrate. 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. Shallow caves are sometimes formed at the base of cliffs by this means. The surface of the trunk is folded like a concertina, allowing it to expand, and a large specimen can hold eight tons of water after a good downpour. [121], The potential for generating solar energy from the Sahara Desert is huge, the highest found on the globe. To encroach upon something means to advance past its usual or natural limits, so when we pair the words “encroachment” and “desert,” we refer to the spread of a desert into surrounding lands.Though “desert” usually conjures up an image of sand, camels, or Lawrence of Arabia; a desert is really any place, regardless of temperature, where average annual precipitation is less than 250mm (about … Orographic lift occurs as air masses rise to pass over high ground. It has been portrayed by writers, film-makers, philosophers, artists and critics as a place of extremes, a metaphor for anything from death, war or religion to the primitive past or the desolate future. They developed skills in the manufacture and use of weapons, animal tracking, finding water, foraging for edible plants and using the things they found in their natural environment to supply their everyday needs. At high wind speeds, sand grains are picked up off the surface and blown along, a process known as saltation. For these reasons, the front line moved back and forth through hundreds of kilometers as each side lost and regained momentum. [113] However, the size and harshness of the terrain meant that all supplies needed to be brought in from great distances. [34], As the mountains are eroded, more and more sand is created. [78] Many examples of convergent evolution have been identified in desert organisms, including between cacti and Euphorbia, kangaroo rats and jerboas, Phrynosoma and Moloch lizards. A dune is a landform composed of wind- or water-driven sand.It typically takes the form of a mound, ridge, or hill. [81] Oxidising a gram of carbohydrate produces 0.60 grams of water; a gram of protein produces 0.41 grams of water; and a gram of fat produces 1.07 grams of water,[82] making it possible for xerocoles to live with little or no access to drinking water. Vegetation plays a major role in determining the composition of the soil. Opinion. Historical Significance . The air is very cold and carries little moisture so little precipitation occurs and what does fall, usually snow, is carried along in the often strong wind and may form blizzards, drifts and dunes similar to those caused by dust and sand in other desert regions. Reptiles cannot survive at this temperature and lizards will be prostrated by heat at 45 °C (113 °F). In some places the wind has carved holes or arches, and in others, it has created mushroom-like pillars narrower at the base than the top. [47], Deserts and semi-deserts are home to ecosystems with low or very low biomass and primary productivity in arid or semi-arid climates. [110] Desertification is caused by such factors as drought, climatic shifts, tillage for agriculture, overgrazing and deforestation. The seed of the mesquite tree, which grows in deserts in the Americas, is hard and fails to sprout even when planted carefully. However, a significant degree of commonality exists among the plant families that dominate different desert vegetations. [7] Polar deserts are a particular class of cold desert. Many solar power plants have been built in the Mojave Desert such as the Solar Energy Generating Systems and Ivanpah Solar Power Facility. This includes much of the polar regions, where little precipitation occurs, and which are sometimes called polar deserts or "cold deserts".
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