| In this brief introduction we will discuss the | | | | the Sierra Vicuna Mackenna. There are more than 20 |
| geographical location of deserts, some of their main | | | | cactus species in the area, mainly of the genus |
| physical features, flora and fauna, effect on climate | | | | Copiapoa The Guanaco is the main mammal found |
| and human use. | | | | in the park. Other mammals include Culpeo Fox, Chilla |
| Main locations and types of Deserts | | | | Fox and European Hare. The shoreline area is home |
| A desert is a landscape or region that receives an | | | | to marine mammals, such as the Marine Otter and |
| extremely low amount of precipitation, less than | | | | the South American Sea Lion. Among the birds are |
| enough to support growth of plants. Deserts are | | | | the Humboldt Penguin and Peruvian Pelican. Also |
| defined as areas with an average annual precipitation | | | | reptile species of the genera Tropidurus and |
| of less than 250 millimetres (10 in) per year or as | | | | Callopistes inhabit the park. |
| areas where more water is lost by | | | | Human Uses |
| evapotranspiration than falls as precipitation. Deserts | | | | Mineral resources |
| are part of a wide classification of regions that, on an | | | | Deserts may contain great amount of mineral |
| average annual basis, have a moisture deficit (i.e. they | | | | resources over their entire surface. This occurrence in |
| can potentially lose more than is received). Deserts | | | | minerals also determines the color. For example, the |
| are located where vegetation cover is sparse to | | | | red color of many sand deserts is a result of the |
| almost nonexistent and make up about one third | | | | occurrence of laterite. .Some mineral deposits too |
| (33%) of the Earth's land surface. This brief | | | | are formed, improved, or preserved by geologic |
| introduction shall concentrate on hot deserts. Hot | | | | processes that occur in arid lands as a consequence |
| deserts usually have a large diurnal and seasonal | | | | of climate. Ground water leaches ore minerals and |
| temperature range, with high daytime temperatures, | | | | redeposits them in zones near the water table. This |
| and low nighttime temperatures (due to extremely | | | | leaching process concentrates these minerals as ore |
| low humidity). In hot deserts the temperature in the | | | | that can be mined. Evaporation in arid lands enriches |
| daytime can reach 45 °C/113 °F or higher in the | | | | mineral accumulation in their lakes. Lake beds known |
| summer, and dip to 0 °C/32 °F or lower in the | | | | as playas may be sources of mineral deposits |
| winter. Dry desert air is incapable of blocking | | | | formed by evaporation. Water evaporating in closed |
| sunlight during the day or trapping heat during the | | | | basins precipitates minerals such as gypsum, salts |
| night. | | | | (including sodium nitrate and sodium chloride), and |
| Thus, during daylight most of the sun's heat reaches | | | | borates. |
| the ground, and as soon as the sun sets the desert | | | | The minerals formed in these evaporite deposits |
| cools quickly by radiating its heat into space. Urban | | | | depend on the composition and temperature of the |
| areas in deserts lack large (more than 14 °C/25 | | | | saline waters at the time of deposition. Significant |
| °F) daily temperature variations, partially due to the | | | | evaporite resources occur in the Great Basin |
| urban heat island effect. Many deserts are formed | | | | Desert of the United States, mineral deposits made |
| by rain shadows; mountains blocking the path of | | | | famous by the "20-mule teams" that once hauled |
| precipitation to the desert (on the lee side of the | | | | borax-laden wagons from Death Valley to the |
| mountain). Deserts are often composed of sand and | | | | railroad. Boron, from borax and borate evaporites, is |
| rocky surfaces. Sand dunes called ergs and stony | | | | an essential ingredient in the manufacture of glass, |
| surfaces called hamada. Exposures of rocky terrain | | | | enamel, agricultural chemicals, water softeners, and |
| are typical, and reflect minimal soil development and | | | | pharmaceuticals. Borates are mined from evaporite |
| sparseness of vegetation. The soil is rocky because | | | | deposits at Searles Lake, California, and other desert |
| of low chemical weathering. The largest hot desert is | | | | locations. The total value of chemicals that have been |
| the Sahara in northern Africa, covering 9 million | | | | produced from Searles Lake substantially exceeds |
| square kilometres and 12 countries. Other large hot | | | | US$ 1 billion The Atacama Desert of Chile is unique |
| deserts include the Arabian Desert, Kalahari Desert, | | | | among the deserts of the world in its great |
| Great Victoria Desert, Great Basin Desert and the | | | | abundance of saline minerals. Sodium nitrate has been |
| Syrian Desert. Deserts are also classified by their | | | | mined for explosives and fertilizer in the Atacama |
| geographical location and dominant weather pattern | | | | since the middle of the 19th century. Nearly 3 million |
| as trade wind, mid-latitude, rain shadow, coastal, | | | | metric tons were mined during World War 1. See our |
| monsoon, or polar deserts. Former desert areas | | | | group Chile Mining and Power on and our other mining |
| presently in non-arid environments are paleodeserts | | | | articles on Articles Base. |
| e.g Nebraska Sand Hills. Montane deserts are arid | | | | Valuable minerals located in arid lands include |
| places with a very high altitude; the most prominent | | | | copper in the United States, Chile, Peru, and Iran, |
| example is found north of the Himalaya especially in | | | | iron and lead zinc ore in Australia; and gold, silver and |
| Ladakh region of Jammu and Kashmir, in parts of the | | | | uranium deposits in Australia and the United States. |
| Kunlun Mountains and the Tibetan Plateau. | | | | Nonmetalic mineral resources and rocks such |
| Many locations within this category have elevations | | | | as beryllium, mica, lithium, clays, pumice, |
| exceeding 3,000 meters (10,000 ft) and the thermal | | | | and scoria also occur in arid regions. Sodium |
| regime can be hemiboreal. These places owe their | | | | carbonate, sulfate, borate,nitrate, |
| profound aridity (the average annual precipitation is | | | | lithium, bromine, iodine, calcium, |
| often less than 40 mm or 1.5 in) to being very far | | | | and strontium compounds come from sediments |
| from the nearest available sources of moisture. | | | | and near-surface brines formed by evaporation of |
| Montane deserts are normally cold. Rain shadow | | | | inland bodies of water, often during geologically |
| deserts form when tall mountain ranges block clouds | | | | recent times. The Green River |
| from reaching areas in the direction the wind is going. | | | | Formation of Colorado, Wyoming, |
| As the air moves over the mountains, it cools and | | | | and Utah contains alluvial fan deposits and playa |
| moisture condenses, causing precipitation on the | | | | evaporites created in a huge lake whose level |
| windward side. When that air reaches the leeward | | | | fluctuated for millions of years. Economically significant |
| side, it is dry because it has lost the majority of its | | | | deposits of trona, a major source |
| moisture, resulting in a desert. The air then warms, | | | | of sodium compounds, and thick layers of oil |
| expands, and blows across the desert. The warm, | | | | shale were created in the arid environment. |
| desiccated air takes with it any remaining moisture in | | | | Some of the more productive petroleum areas on |
| the desert. An example of a rain shadow desert is | | | | Earth are found in arid and semiarid regions of Africa |
| Death Valley which lies in the rain shadow of the | | | | and the Mideast, although the oil fields were |
| Pacific Coast Ranges of California and the Sierra | | | | originally formed in shallow marine environments. |
| Nevada Mountains. | | | | Recent climate change has placed these reservoirs in |
| Main Physical Features | | | | an arid environment. It's noteworthy that Ghawar, |
| Sand covers only about 20 percent of Earth's | | | | the world's largest and most productive oilfield is |
| deserts. Most of the sand is in sand sheets and sand | | | | mostly under theEmpty |
| seas—vast regions of undulating dunes. In general, | | | | Quarter and Al-Dahnadeserts. For more oil |
| there are six forms of deserts: 1) Mountain and basin | | | | information please check out Other oil reservoirs, |
| deserts 2) Hamada deserts, which consist of plateau | | | | however, are presumed to be eolian in origin and |
| landforms 3) Regs, which consist of rock pavements | | | | are presently found in humid environments. |
| 4) Ergs, which are formed by sand seas 5) | | | | The Rotliegendes, a hydrocarbon reservoir in |
| Intermontane Basins and 6) Badlands, which are | | | | the North Sea, is associated with extensive |
| located at the margins of arid lands comprising | | | | evaporite deposits. Many of the major U.S. |
| clay-rich soil Nearly all desert surfaces are plains | | | | hydrocarbon resources may come from eolian sands. |
| where eolian deflation—removal of fine-grained | | | | Ancient alluvial fan sequences may also be |
| material by the wind—has exposed loose gravels | | | | hydrocarbon reservoirs. |
| consisting predominantly of pebbles but with | | | | Solar energy resources |
| occasional cobbles. The remaining surfaces of arid | | | | Deserts are increasingly seen as sources for solar |
| lands are composed of exposed bedrock outcrops, | | | | energy. The Negev Desert and the surrounding |
| desert soils, and fluvial deposits including alluvial fans, | | | | area, including the Arava Valley, are the sunniest |
| playas, desert lakes, and oases. Bedrock outcrops | | | | parts of Israel and little of this land is arable, which is |
| occur as small mountains surrounded by extensive | | | | why it has become the center of the Israeli solar |
| erosional plains. Several different types of dunes | | | | industry. David Faiman, a world expert on solar |
| exist. Barchan dunes are produced by strong winds | | | | energy, feels the energy needs of a country |
| blowing across a level surface and are | | | | like Israel could be met by building solar energy |
| crescent-shaped. Longitudinal or seif dunes are dunes | | | | plants in the Negev. Faiman also feels the technology |
| that are parallel to a strong wind that blows in one | | | | now exists to supply all of the world's electricity |
| general direction. Transverse dunes run at a right | | | | needs with 10 per cent of the Sahara. Solel has nine |
| angle to the constant wind direction. Star dunes are | | | | fields of solar collectors in the Mojave Desert of |
| star-shaped and have several ridges that spread out | | | | California It recently signed a contract to build |
| around a point. Oases are vegetated areas | | | | the Mojave Solar Park, which will be the world's |
| moistened by springs, wells or by irrigation. Many are | | | | largest solar generating plant. |
| artificial. Oases are often the only places in deserts | | | | Human life in deserts |
| that support crops and permanent habitation. | | | | A desert is a hostile, potentially deadly environment |
| Flora and Fauna | | | | for unprepared humans. In hot deserts, high |
| Deserts have a reputation for supporting very little | | | | temperatures cause rapid loss of water due to |
| life, but in reality deserts often have high biodiversity, | | | | sweating, and the absence of water sources with |
| including animals that remain hidden during daylight | | | | which to replenish it can result in dehydration and |
| hours to control body temperature or to limit | | | | death within a few days. In addition, unprotected |
| moisture needs. Some fauna for example in the | | | | humans are also at risk from heatstroke. Humans |
| Mojave desert includes the brush mouse, cactus | | | | may also have to adapt to sandstorms in some |
| mouse, gray fox, porcupine, kangaroo rat, coyote, | | | | deserts, not just in their adverse effects |
| jack rabbit and many kinds of lizards. In the Australian | | | | on respiratory systems and eyes, but also in their |
| deserts we have the Bilby, Perentie, Thorny Devil, | | | | potentially harmful effects on equipment such |
| Bearded Dragon, Red Kangaroo and Dingo as | | | | as filters, vehicles and communication equipment. |
| examples. These animals adapted to live in deserts | | | | Sandstorms can last for hours, sometimes even days. |
| are called xerocoles. Many desert animals (and plants) | | | | This makes surviving in the desert quite difficult for |
| show especially clear evolutionary adaptations for | | | | humans. Despite this, some cultures have made hot |
| water conservation or heat tolerance, and so are | | | | deserts their home for thousands of years, including |
| often studied in comparative physiology, | | | | the Bedouin, Tuareg and Pueblo people. |
| ecophysiology and evolutionary physiology. | | | | Modern technology, including |
| One well-studied example is the specializations of | | | | advanced irrigation systems, desalinization and air |
| mammalian kidneys shown by desert-inhabiting | | | | conditioning have made deserts much more |
| species. Many examples of convergent | | | | hospitable. In the United States and Israel for |
| evolution have been identified in desert organisms, | | | | example, desert farming has found extensive use |
| including between cacti and Euphorbia, kangaroo rats | | | | and locations such as Las Vegas owe much to air |
| and jerboas, Phrynosoma and Moloch lizards. Some | | | | conditioning. In cold |
| flora includes shrubs, Prickly Pears, Desert Holly, and | | | | deserts, hypothermia and frostbite are the chief |
| the Brittlebush. Most desert plants are drought- or | | | | hazards, as well as dehydration in the absence of a |
| salt-tolerant, such as xerophytes. Some store water | | | | source of heat to melt ice for drinking. Falling through |
| in their leaves, roots, and stems. Other desert plants | | | | pack-ice or surface ice layers into freezing water is a |
| have long taproots that penetrate to the water | | | | particular danger requiring emergency action to |
| table if present, or have adapted to the weather by | | | | prevent rapid hypothermia. Starvation is also a |
| having wide-spreading roots to absorb water from a | | | | hazard; in low temperatures the body requires much |
| greater area of the ground. Another adaptation is | | | | more food energy to maintain body heat and to |
| the development of small, spiny leaves which shed | | | | move. As with hot deserts, some people such as |
| less moisture than deciduous leaves with greater | | | | the Inuit have adapted to the harsh conditions of |
| surface areas. | | | | cold deserts. Most traditional human life in deserts |
| The stems and leaves of some plants lower the | | | | is nomadic. It depends in hot deserts on finding |
| surface velocity of sand-carrying winds and protect | | | | water, and on following infrequent rains to obtain |
| the ground from erosion. Even small fungi and | | | | grazing for livestock. In cold deserts, it depends on |
| microscopic plant organisms found on the soil surface | | | | finding good hunting and fishing grounds, on sheltering |
| (so-called cryptobiotic soil) can be a vital link in | | | | from blizzards and winter extremes, and on storing |
| preventing erosion and providing support for other | | | | enough food for winter. Permanent settlement in |
| living organisms. Deserts typically have a plant cover | | | | both kinds of deserts requires permanent water and |
| that is sparse but enormously diverse. The giant | | | | food sources and adequate shelter, or the |
| saguaro cacti of the Sonoran Desert provide nests | | | | technology and energy sources to provide it. Many |
| for desert birds and serve as "trees" of the desert. | | | | deserts are flat and featureless, lacking landmarks, or |
| Saguaro grow slowly but may live up to 200 years. | | | | composed of repeating landforms such as sand |
| When 9 years old, they are about 15 centimeters (6 | | | | dunes or the jumbled ice-fields of glaciers. Advanced |
| in) high. After about 75 years, the cacti develop their | | | | skills or devices are required to navigate through such |
| first branches. When fully grown, saguaro cacti are 15 | | | | landscapes and inexperienced travellers may perish |
| meters tall and weigh as much as 10 tons. They dot | | | | when supplies run out after becoming lost. In addition |
| the Sonoran and reinforce the general impression of | | | | sandstorms or blizzards may cause disorientation in |
| deserts as cactus-rich land. Although cacti are often | | | | severely reduced visibility. |
| thought of as characteristic desert plants, other | | | | The danger represented by wild animals in deserts |
| types of plants have adapted well to the arid | | | | has been featured in explorers' accounts but does |
| environment. They include the pea and | | | | not cause higher rates of death than in other |
| sunflower families. Cold deserts have grasses and | | | | environments such as rain forests or savanna |
| shrubs as dominant vegetation. | | | | woodland, and generally does not by itself affect |
| Biodiversity Case Study - The Atacama | | | | human distribution. Defence against polar bears may |
| Atacama is the driest place on Earth and is virtually | | | | be advisable in some areas of the Arctic, as may |
| sterile because it is blocked from moisture on both | | | | precautions against venomous |
| sides by the Andes mountains and by the Chilean | | | | snakes and scorpions in choosing sites at which |
| Coastal Range. The cold Humboldt Current and the | | | | to camp in some hot deserts. However, it is hard to |
| anticyclone of the Pacific are essential to keep the | | | | overestimate the importance of deserts in our |
| dry climate of the Atacama. The average rainfall in | | | | cultural and historical background. Three of the |
| the Chilean region of Antofagasta is just 1 mm per | | | | World's largest religions Christianity, Islam and Judaism |
| year. Some weather stations in the Atacama have | | | | began and are set against a desert backdrop. All |
| never received rain. Evidence suggests that the | | | | three religions are monotheistic, and today have |
| Atacama may not have had any significant rainfall | | | | enormous geopolitical influence extending far beyond |
| from 1570 to 1971. It is so arid that mountains that | | | | their area of origin -see articles on Christianity here |
| reach as high as 6,885 meters (22,590 feet) are | | | | on Articles Base and Biblon Deserts are also now a |
| completely free of glaciers and, in the southern part | | | | major source of tourism and travel interest e.g. |
| from 25°S to 27°S, may have been glacier-free | | | | Joshua Tree, Death Valley National Parks as well as |
| throughout the Quaternary, though | | | | vital to the movie industry. |
| permafrost extends down to an altitude of 4,400 | | | | Deserts are also vital areas for scientific interest. - |
| meters and is continuous above 5,600 meters. | | | | specific examples include Deep Canyon on the |
| Some locations in the Atacama do receive a marine | | | | western edge of the Colorado Desert is associated |
| fog known locally as the Camanchaca, providing | | | | with the University of California, Riverside located in |
| sufficient moisture for hypolithic algae, lichens and | | | | the P.L. Boyd Deep Canyon Desert Research Center. |
| even some cacti. But in the region that is in the "fog | | | | It receives a variety of visiting scientists and |
| shadow" of the high coastal crest-line, which | | | | students and, in addition to research, addresses |
| averages 3,000 metres (10,000 ft) m height for | | | | conservation issues of the surrounding environment |
| about 100 kilometres (60 mi) south of Antofagasta, | | | | such as the fate of the fringe-toed lizard. Another |
| the soil has been compared to that of Mars. Due to | | | | desert centre established by one visionary biologist, |
| its otherworldly appearance, the Atacama has been | | | | the Gobabeb Training and Research Centre, is located |
| used as a location for filming Mars scenes. The desert | | | | in Namibia within the driest part of the coastal Namib |
| was also primarily featured in the 2008 James Bond | | | | Desert in the Namib-Naukluft Park. As the United |
| film Quantum of Solace. In 2003, a team of | | | | Nations Environment Program concludes "People have |
| researchers published a report in Science | | | | lived in deserts for millennia, as hunter-gatherers, |
| Magazine titled "Mars-like Soils in the Atacama | | | | agriculturalists and pastoralists, and some people |
| Desert, Chile, and the Dry Limit of Microbial Life" in | | | | continue to do so today. But other people now live in |
| which they duplicated the tests used by the Viking 1 | | | | urban developments situated in deserts, or enjoy |
| and Viking 2 Mars landers to detect life, and were | | | | deserts temporarily for tourism or recreation. Yet |
| unable to detect any signs in Atacama Desert soil. | | | | others are extracting profits from mining or other |
| The region may be unique on Earth in this regard and | | | | non-renewable resources. Deserts are a large and |
| is being used by NASA to test instruments for | | | | probably growing environment globally and their |
| future Mars missions. Let us take a closer look at | | | | future will be best supported if it is based on a |
| some of the biology of a particular region of the | | | | thorough understanding of their structure and |
| Atacama - the nearby Pan de Azucar National Park. | | | | function, and the influence of people's activities in the |
| Pan de Azúcar NP is divided into two ecosystems: | | | | past, present and future. |
| the coastal desert of Taltal and the steppe desert of | | | | |