Yuma Desert | desert, North America | Britannica.com desert, North America Atacama Desert Yuma Desert, arid part of the Sonoran Desert . It lies south of the Gila River and east of the Colorado River in the extreme southwestern corner of Arizona , U.S. , and in the northwestern corner of Sonora , Mexico . The desert south of the Mexican border often is called the Great Desert (Spanish: Gran Desierto). The Yuma Desert is a region of low sandy plains and dunes. The area is nearly barren, with only sporadic outcroppings of creosote bush or burr sage. With the Colorado Desert of southern California , U.S., and Baja California , Mex., the Yuma Desert occupies a landform known as the Salton Trough (Salton Basin). Extensive irrigation works divert water from dams on the Colorado River to support large-scale commercial agriculture in the Colorado and Gila river valleys (winter vegetables, cotton, flax, citrus fruits, dates, and alfalfa); however, the rivers themselves have been greatly disrupted by these and other water-diversion projects and flow only intermittently in their respective lower reaches.

The Yuma Desert’s clear skies and low precipitation favour activities at the U.S. Marine Corps Air Station at the city of Yuma. Learn More in these related articles: Corrections? Updates? Help us improve this article! Contact our editors with your feedback. MEDIA FOR: You have successfully emailed this. Error when sending the email. Try again later. Edit Mode Submit Tips For Editing We welcome suggested improvements to any of our articles. You can make it easier for us to review and, hopefully, publish your contribution by keeping a few points in mind. Encyclopædia Britannica articles are written in a neutral objective tone for a general audience. You may find it helpful to search within the site to see how similar or related subjects are covered. Any text you add should be original, not copied from other sources. At the bottom of the article, feel free to list any sources that support your changes, so that we can fully understand their context. (Internet URLs are the best.) Your contribution may be further edited by our staff, and its publication is subject to our final approval. Unfortunately, our editorial approach may not be able to accommodate all contributions. Submit Thank You for Your Contribution!

Our editors will review what you've submitted, and if it meets our criteria, we'll add it to the article. Please note that our editors may make some formatting changes or correct spelling or grammatical errors, and may also contact you if any clarifications are needed. Uh Oh There was a problem with your submission. Please try again later. Close Date Published: October 26, 2015 URL: Access Date: January 04, 2017 Share The desert shows you nothing; you must find everything. al-Hamada(h) al-Hamra(h) Sahara: Tenere: Tanzerouft, الصحراء The awesome Sahara is the largest desert on the planet earth, with an estimated size of between seven and nine million square kilometres (9,000,000 sq km). Its shortest distance from north to south is about 1000 miles. To imagine the scale of this gigantic size, the Sahara occupies a third of Africa and is as large as the continent of Europe.

It is made of a number of smaller deserts including the Libyan desert in Libya and Egypt, the Central Sahara in Libya and Algeria (including the Ahoggar Mountains, the Tibesti Mountains, the Air Mountains, and Tenere), and the Western Sahara; stretching across the whole of North Africa, from the Red Sea to the Atlantic Ocean and from the Mediterranean to Chad and the Sudan; with Tibesti's Emi Koussi being its highest peak (3,415 m/11,200 ft). Courtesy of Nasa The origin of The Sahara Hundreds of millions of years ago the Sahara was covered by a great sea called the Tethys Sea. Around 40 million years ago the tectonic plates gradually began pushing Africa against Europe for 20 million years. Around 20 million years ago Africa collided with Europe and closed the Tethys Sea. As Africa continued to push against Europe northern Africa began to slowly emerge from the bottom of the sea; leaving behind a tropical swamp. Eventually the swamps turned into massive expanse of searing desert around 3 million years ago. See documentary at the end of this page for details. This image is a screenshot from this documentary .

Around 800,000 years ago, the Sahara was hot, damp and covered with swamps and vegetation everywhere. This period of heavy rain lasted for hundreds of thousands of years; leaving behind wet and lush-green land, covered with rivers and lakes, and teeming with hippopotami, rhinoceroses, crocodiles and elephants; as well as three megalakes (giant lakes of fresh water): one lake was situated in Tunisia (the tiny Chott el Djerid of today, the ancient Lake Tritonis); the second megalake was in southern Libya (the Fezzan lakes of today ); and the third is the Chad megalake in Chad. According to the Sahara Megalakes Project, Megafezzan is the only lake that provides long term record of climate change in the central Sahara. Ever since, the Sahara comes and goes just as ice ages do elsewhere.

However, according to an article published in the Independent Newspaper (September 8, 1999), titled: "Tilt of Earth's axis turned Sahara into a desert", scientists have found that the Sahara was abruptly transformed from fertile land into a desert after the Earth underwent one of its periodic changes in orientation between 9000 and 6000 years ago; during which its tilt lessened from 24.14 degrees off vertical to its present 23.45 degrees, and its closest position to the sun gradually shifted from July to January. This documentary shows the last cycle to have started around 5,500 years ago; after which the inhabitants of the Sahara left to build the great civilisation of all times: the Egyptian civilisation along the Nile. Scientists say 15,000 years from now the tilt of the Earth will turn the Sahara green once more; and therefore each dry-green cycle is around 20,000 years long. Sahara Types The Sahara is not a permanent feature of the landscape, but is a continuously changing phenomenon that comes and goes just as ice ages do across time.

The last visit was about 5000 years ago, when the Sahara began its current cycle after its lakes and rivers dried up into thin air. All it remained are its prehistoric engravings, paintings and rock petroglyphs of extinct life, and some of the lakes. (See Sahara Wildlife page for more on these periods). Contrary to conception, only a quarter of the Sahara is covered with sand and sand dunes, some of which are nearly 200 metres high. Occasionally, sand dust from the Sahara has been carried as far north as Germany and the United Kingdom, and as far west as the Americas. The rest of the Sahara is mainly: Mountains (25%) and dry valleys: like the Hoggar mountains in Algeria, Air mountains in Niger, and Tibesti (also written as Tibisti) in Chad (with a small section in Libya). Rocks, stone plateaux and gravel plains. Oases, like Ghadames and Ghat. Sand Seas: sand with sparse vegetation: as in the Western Sahara, Libyan Desert, Ubari Sand Sea, and Murzuk Sand Sea, and also found in mini rocky deserts, like Acacus and al Hamada.

Definitions Sahara Eco-Regions 1- North Saharan: (1,675,300 square km): the far northern part of the Sahara, just below the coasts of Egypt, Libya, Algeria, Morocco. A midway point between the Mediterranean climate and the Sahara proper. 2- Sahara Central: (4,639,900 square km): mainly sand dunes, ergs, hamadas and dry valleys, in Libya, Egypt, Chad, Algeria. Mainly dry, rare rain, scarce vegetation.. 3- Atlantic Coastal: (39,000 square km): along the Atlantic coast, in the Western Sahara and Mauritania. Moisture from the Atlantic Ocean sustains a small community of plants. 4- West Saharan: (258,100 square km): Saharo-Mediterranean climate, in Tassili n Ajjer, Air in Niger, Dhar Adrar in Mauritanian, and Iforas Mountain in Mali and Algeria.

5- Saharan Halophytics: (54,000 square km): saline depressions sustain salt-adapted plants, in Swia (in Egypt), and in the western Libyan and southern Tunisian salt marshes and lakes. 6- Tanezrouft ('desert'): dry and totally bare desert region, along the borders of Mali, Niger and Algeria, just west of the Hoggar Mountains. 7- South Saharan: (1,101,700 square km): a narrow strip between the central Sahara and southern sahel savanah. Summer rain sustain some plants and grasses in Sudan, Chad, Mali, Algeria, Mauritania. 8- South-South-East Saharan: Tibesti and Uwaynat Mountains (82,200 square km): more rain and lower temperatures sustain a family of trees and bushes including acacias, palm trees, myrtles and Tamarix, in northern Chad, southern Libya (by the Sudanese border). Temperature In The Sahara Winters in the subtropical north can be very cold where temperatures can fall below freezing point, as opposed to the mild tropical south, where rain falls more during the summer than it does in the north.

Similarly, temperatures are high during the day and low at night. Although in the summer the temperature can reach 50 degrees Celsius in the shade and in the winter can reach -9 (minus nine), the average year round temperature is about 30 degrees Celsius. Between the 27th of December and the 18th of January some area of the Sahara becomes covered with a thin white layer very similar to frost in Europe, which turns the surface white and hence the name: "The White Nights". Wind In The Sahara One of the main features of the wind in the Sahara is its ability to change the surrounding landscape by shifting sand from one area to another; leading to the formation of sand dunes on roads, where driving at night becomes very dangerous. The worst time to visit the Sahara is between March and April largely because of the wind: very windy almost every single day, especially near the end of March and most of April. It is also common to see archaeological artifacts, like flints, stone tools, pottery shreds and bones, exposed by the wind and scattered across the surface of the Sahara. These are part of Libya and the world's heritage and history and therefore should be left where they are. Not doing so could lead to prosecution.

The effects of the wind, exposing stones, flints, and stone-age tools. The Libyan Sahara The Libyan Sahara can be further divided into several smaller deserts or regions. For convenience, Libya may be divided into three sections (from top to bottom): the Western section (starting from the top and all the way down to Acacus); the Middle section (from Surt and all the way down to Sarir Tibesti); and the Eastern section (Cyrenaica and the Libyan desert, all the way to Kufra and down to the border with Sudan. The Western Section Al-Hamada al-Hamra (the Red Plateau): a mixture of sand seas and rocky plains, immediately below the Western Mountain and all the way down to Awbari Sand Sea and Wadi Ash Shati. Often accessed via Daraj and Ghadames. Idhan Ubari (or Awbari Sand Sea): a sand desert of magnificent sand dunes and desert lakes, starting from the Algerian border and extending east to Sabha.

Bordered from the south by Hamadat Zigher (west) and Wadi al Hayat (the Valley of Life), where a strip of oases and settlements cuts through from Sabha to Awaynat near the Algerian border. Ghat: immediately below Idhan Awbari: includes three mountains: Acacus, and Messak Mellet & Messak Settafet, separated by Wan Casa (a narrow strip of sand running along the Acacus mountain from south to north). It is often used to enter the Acacus Mountain either coming down from Serdeles (Awaynat) or from Wadi Metkhandoush via the Messak Settafet. Idhan Murzuq (Murzuk Sand Sea): immediately west of the Messak Millet and all the way east to Jabal Ghunaymah. The Middle Section The Pre-Desert: this term is generally used to refer to the area before the desert proper, just below Misrata and immediately to the west of the Western Mountain, which includes sites like Ghirza.

Sahara Surt (Surt Desert): this mini desert is located below the Gulf of Surt (Syrtis) and between Tripolitania and Cyrenaica, which includes Waddan Mountain and the Black Mountain (Asawda'). The Black Haruj Mountain: right at the centre of Libya, with a summit of 1200 meters (Qaraf as Sabah), and surrounded by a huge area of lava flow, which accounts for its name. Accessed from Zillah (in the north) via a track that cuts through the mountain all the way south to Tmassah and Waw al-Kabir. Sarir Tibesti: from Waw al Kabir one can turn west and enter Sarir as-Sabah and then Bin Ghunaymah mountain (the site of several Garamantean and Stone Age discoveries); or continue south towards Sarir Tibesti (which extends a bit into Chad) and south-west towards Waw an-Namus. Rebiana Sand Sea: from Waw an-Namus one tracks east across the huge Ramlat Rabyanah (Rebiana Sand Sea) towards Tazirbo (in the Eastern Section).

The Eastern Section Marmarica (al-Butnan): a small desert area starting immediately below the coast and between the Green Mountain and the Egyptian border in Cyrenaica, and extends all the way down to the great sand seas and Al Kufrah. The Great Sand Sea & Calanscio Sand Sea: these great sand seas separate Cyrenaica from the Libyan desert proper in the south and along the Egyptian border; with various oases: Jaghbub (by the border), Awjilah, Jalu, and various oil fields. As-Sah'ra' al-Libiyyah (the Libyan Sahara, also known as the Libyan Desert ): occupying much of south-east Libya and extends into Egypt, which includes: Rebiana Sand Sea (coming from Waw an-Namus), and then Zighan, Buzaymah, Rebiana and al-Jawf; from which one can either head north towards Jalu (via a tarmac road), or track south towards Jebel Uweinat. Jabal al Uwaynat (Jebel Uweinat), close to the Egyptian border: also the site of prehistoric art.

The Languages Spoken in the Sahara The main language spoken in the desert is Tamasheght or Tamazeght (Tamazight), the Berber language of the nomadic Tuareg people, who inhabited the Sahara from immemorial times. The Tuareg tribes are found in several countries including Libya, Chad, Niger, Mali, Algeria, Burkina Faso, northern Nigeria, Mauritania and the Western Sahara. Other none-Tuareg Berber-speaking areas include Siwa (in Egypt), Jalu and Awjilah (in Libya), and other villages in southern Tunisia, Algeria and Morocco. Other languages spoken in the Sahara include: Arabic (of Egypt, Libya, Mauritania and the Western Sahara), Beja (of the Red Sea), Nilo-Saharan (of the western Sudan including the Fur of Darfur, and the Tbawi of the Tebo of Libya), and the Saharan languages (of Niger and Chad including Kanuri, Tedaga and Dazaga). The Berber, Chadic and Arabic languages are members of the Afro-Asiatic linguistic family (originally the Hamito-Semitic Family), of North, Central and North-East Africa.

The Red Sahara Desert Alhamada Alhamra Hammada al Hamada or Alhamadah al Hamra (or al Hamrah) means The Red Plateau, probably in reference to its vibrant, ochry, red colour. In contrast, other districts of the Sahara are strictly golden, particularly with their calcite specks shimmering like desert stars. The Red Hamada is a large area located in north-west Libya, at the entrance to the great desert, coming from the western mountain via Daraj, Ghadames and Qaryat. Hundreds of meteorites smash onto her surface as far north as Daraj. (See our Daraj page for a link to a list of Daraj meteorites). The red plateau is a mixture of rocky terrains, mountains, valleys, tracks, sandy plains and deserts; very popular among Sahara adventure travellers, who often cross it from Daraj to Adiri via Awaynat Wanin, and from there continue into the Awbari Sand Sea towards the famous Fezzan lakes. After the lakes, one briefly returns to civilisation at Sabha, Awaynat and Germa - the home of the ancient civilisation of the Berber Garamantes, before venturing into: Acacus.

The Golden Acacus Entering The Golden Acacus. Somehow one often hears about 'ancient places', like ancient Egypt and the more recent ancient Rome, but only in Acacus that one can actually feel "ancient". You would instantly realise a new alien landscape, hidden back in time and well isolated from the outside world. Secrets of unknown civilisations and episodes of human's distant history withstood the onslaught of time in solitary caves for more that 12,000 years. No visit to the desert is complete without seeing Acacus. Acacus Stone Formations. Sphynx-like natural sculpture from Acacus. The Black Sahara Waw an-Namus volcano is located south-east of the Harouj Alaswad Mountain (The Black Harouj Mountain), and not far from Tibesti Mountain by the Chadian border. The volcanic field of Waw an-Namus is surrounded by an area of black deposit of ash, between 10 and 20 kilometres wide, which accounts for its online nickname: the Dark Spot, as it appeared in Google Earth.

Water Sources in the Sahara The Sahara is green only where there is water, otherwise it is white, beige, yellow, caramel, gold, brown, red or black. Water sources in the desert include several water wells, lakes, underground tables and rain. Water wells in the Acacus desert are clearly marked on the EWP Jebel Acacus map, like Aminanegh, Talwawat, Sughd and Abankur, as well as several gheltas (or water holes), in In Farden, Tin Lalen and Wadi Bubu. Rain: average rainfall: between 0 and 25 mm per annum; scarce but brings the valleys back to life, and hence the name: the Valley of Life in Fezzan. Lakes: there are several lakes in the desert, mostly in the Awbari Sand Sea. These were part of, or left over from, the ancient giant lake known as Megafezzan Lake. The source of this water is usually a water table under the surface of the desert, which intercepts the land surface where the lakes are located.

There are huge water reserves under the Sahara, just like oil, which the Great Man Made River intercepts to pump to the coastal towns and cities of Libya - an idea which may had its origin in the Garamantean "foggaras" - an ancient system of channels used to channel the liquid-of-life from underground reserves to farms. After rain, the dry valleys come to life again to sustain some desert shrubs and bushes. The Sahara Forest Project Covering less than 1% of the world’s deserts with concentrating solar power plants could produce 100% of the electricity used in the whole world. In addition to oil, gas, minerals and underground water reserves, potential investors and governments have set their eyes on the Sahara as a source of infinite energy. The staggering temperature degrees apparently can turn the arid desert into a gigantic storehouse of solar energy. Environmentalists and critics have strongly objected to the project being labeled "green" and "natural", and argue that this kind of expensive energy will not benefit the local poor populations of the Sahel, just as most Europeans nowadays spend the harsh winter nights shivering with hope because their low wages cannot match the staggering costs of energy bills.

Others even went on to say the project is a European ploy to deploy the Sahara to power future Europe when oil becomes history. While enthusiasts stress that current methods of supplying arid regions with water, such as over-abstraction from underground reserves and diverting water from other regions, are not sustainable and could lead to conflict in the long run. As often is the case fact and fiction are not hard to obfuscate. Covering less than 1% of the world’s deserts with concentrating solar power plants could produce 100% of the electricity used in the whole world. Image from exploration-architecture.com The Sahara Forest Project was first proposed at the third Claverton Energy Group Conference, at Wessex Water Plc headquarters, on April 13, 2008. The SFP was the brainchild of Bill Watts, Charlie Paton and Michael Pawlyn. The name "Sahara" is used here to mean what the word 'Sahara' means: namely 'desert', and therefore it includes any desert in the world, although the focus point is the Sahara herself.

The project aims to provide a source of renewable energy, food and water to desert regions around the world, by using two technologies: Seawater Greenhouse technology (SG) and Concentrated Solar Power (CSP). The former creates fresh water from seawater via especially designed greenhouses, which also provide food-growing environment; while the latter produces electricity from sunlight at a fraction of the cost of photovoltaics, via special mirrors used to condense (or concentrate) sunlight to create heat, which then is used to drive conventional steam turbines to generate the needed electricity. It was estimated that it will cost around $59 billion to begin producing energy by 2020, and that to start sending significant amounts of energy from North Africa to Europe one needs to spend about $465 billion over the next 40 years. Hence it does not come as a surprise when the French President Nicolas Sarkozy proposed the construction of a new solar-power station in the Sahara last year, when he founded the Mediterranean Union: a strategic alliance of 43 countries from Europe, North Africa and the Middle East. Who knows, maybe North African countries will have something more valuable in the future than the oil currently their countries have but which they cannot enjoy.

In contrast to winter fuel-bills in Europe, only some lucky Libyans and Saharans can enjoy the cool breeze of expensive air-conditions seen at the Rixos hotel - where the leaders sit to decide the destiny of the impoverished population(s). It is not a question of what the earth has to offer the country, as much as what the leaders and their policies have to share with people. Oil will certainly run out, and other sources of energy must be found. The Sun is the best source of pure and clean energy in our Solar System, as it is guaranteed to shine for an estimated 5 billion more years - although the last two billion years of its life will be far too-hot to sustain any form of life but lava - just as it started its 10 billion years cycle. Top Ten Largest Deserts in the World | The Wondrous Top Ten Largest Deserts in the World Nature, Top Ten Pinterest0 10. Kara-Kum Desert, Uzbekistan / Turkmenistan In our list of largest deserts in the world at #10 is The Karakum Desert, also spelled Kara-Kum and Gara Gum is a desert in Central Asia.

It occupies about 70 percent, or 350,000 km², of the area of Turkmenistan. Covering much of present day Turkmenistan, the Karakum Desert lies east of the Caspian Sea, with the Aral Sea to the north and the Amu Darya river and the Kyzyl Kum desert to the northeast. In modern times, with the shrinking of the Aral Sea, the extended “Aral Karakum” has appeared on the former seabed, with an estimated area of 15,440 sq. The sands of the Aral Karakum are made up of a salt-marsh consisting of finely-dispersed evaporites and remnants of alkaline mineral deposits, washed into the basin from irrigated fields. The dusts blown on a powerful east-west airstream carry pesticide residues that have been found in the blood of penguins in Antarctica. Lets read about top ten largest deserts in the world. 9. Great Sandy Desert, Australia The Great Sandy Desert is a 360,000 km2 (140,000 sq mi) expanse in northwestern Australia.

Roughly the same size as Japan, it forms part of a larger desert area known as the Western Desert. The vast region of Western Australia is sparsely populated, without significant settlements. The Great Sandy Desert is a flat area between the rocky ranges of the Pilbara and the Kimberley. To the southeast is the Gibson Desert and to the east is the Tanami Desert. The Rudall River National Park and Lake Dora are located in the southwest while Lake Mackay is located in the southeast. Image credit: yaruman5 8. Chihuahuan Desert, Mexico The Chihuahuan Desert is a desert that straddles the U.S.-Mexico border in the central and northern portions of the Mexican Plateau, bordered on the west by the extensive Sierra Madre Occidental range, and overlaying northern portions of the east range, the Sierra Madre Oriental. On the U.S.

side it occupies the valleys and basins of central and southern New Mexico, Texas west of the Pecos River and southeastern Arizona; south of the border, it covers the northern half of the Mexican state of Chihuahua, most of Coahuila, north-east portion of Durango, extreme northern portion of Zacatecas and small western portions of Nuevo León. It has an area of about 140,000 square miles. It is the third largest desert of the Western Hemisphere and is second largest in North America, after the Great Basin Desert. Via: wikipedia 7. Great Basin Desert, USA The Great Basin is the largest watershed of North America which does not drain to an ocean. Water within the Great Basin evaporates since outward flow is blocked. The basin extends into Mexico and covers most of Nevada and over half of Utah, as well as parts of California, Idaho, Oregon and Wyoming. The majority of the watershed is in the North American Desert ecoregion, but includes areas of the Forested Mountain and Mediterranean California ecoregions. The Great Basin includes several metropolitan areas and Shoshone Great Basin tribes. A wide variety of animals can be found in great basin desert.

Look to the rocky slopes around the desert mountain ranges, you may spot a very rare desert bighorn sheep. Other mammals of the desert include kit fox, coyote, skunk, black-tailed jackrabbit, ground squirrels, kangaroo rat and many species of mice. Bird species are very diverse in desert oases. Via: wikipedia 6. Great Victoria Desert, Australia The Great Victoria Desert is a barren, arid, and sparsely populated desert ecoregion in southern Australia. It falls inside the states of South Australia and Western Australia and consists of many small sandhills, grasslands and salt lakes. It is over 700 kilometres (430 mi) wide (from west to east) and covers an area of 424,400 square kilometres (163,900 sq mi). The Western Australia Mallee shrub ecoregion lies to the west, the Little Sandy Desert to the northwest, the Gibson Desert and the Central Ranges xeric shrublands to the north, the Tirari and Sturt Stony deserts to the east, and the Nullarbor Plain to the south separates it from the Southern Ocean. Image credit: Travel Collective 5.

Patagonia Desert, Argentina The Patagonian Desert, also known as the Patagonia Desert or the Patagonian Steppe, is the largest desert in America and is the 7th largest desert in the world by area, occupying 260,000 square miles (673,000 km). It is located primarily in Argentina with small parts in Chile and is bounded by the Andes, to its west, and the Atlantic Ocean to its east, in the region of Patagonia, southern Argentina. The Patagonian Desert is the largest continental landmass of the 40° parallel and is a large cold winter desert, where the temperature rarely exceeds 12°C and averages just 3°C. The region experiences about seven months of winter and five months of summer. Image credit: Melissa Toledo 4. Kalahari Desert, Southern Africa The Kalahari Desert is a large arid to semi-arid sandy area in Southern Africa extending 900,000 square kilometers (350,000 sq), covering much of Botswana and parts of Namibia and South Africa, as semi-desert, with huge tracts of excellent grazing after good rains.

The Kalahari Desert is the southern part of Africa, and the geography is a portion of desert and a plateau. The Kalahari supports some animals and plants because most of it is not a true desert. There are small amounts of rainfall and the summer temperature is very high. It usually receives 3–7.5 inches (76–190 mm) of rain per year. The surrounding Kalahari Basin covers over 2,500,000 square kilometers (970,000 sq mi) extending farther into Botswana, Namibia and South Africa, and encroaching into parts of Angola, Zambia and Zimbabwe. The only permanent river, the Okavango, flows into a delta in the northwest, forming marshes that are rich in wildlife. Via: wikipedia 3. Gobi Desert, Mongolia / N.E China The Gobi is a large desert region in Asia. It covers parts of northern and northwestern China, and of southern Mongolia.

The desert basins of the Gobi are bounded by the Altai Mountains and the grasslands and steppes of Mongolia on the north, by the Hexi Corridor and Tibetan Plateau to the southwest, and by the North China Plain to the southeast. The Gobi is made up of several distinct ecological and geographic regions based on variations in climate and topography. This desert is the fifth largest in the world. The Gobi is most notable in history as part of the great Mongol Empire, and as the location of several important cities along the Silk Road. Image Credit: PnP 2. Arabian Desert, peninsula Arabian Desert or Eastern Desert, c.86,000 sq mi (222,740 sq km), E Egypt, bordered by the Nile valley in the west and the Red Sea and the Gulf of Suez in the east. It extends along most of Egypt’s eastern border and merges into the Nubian Desert in the south. The Arabian Desert is sparsely populated; most of its inhabitants are based around wells and springs. Today most of the desert can be accessed by roads.

Since ancient times Egypt has used the porphyry, granite, limestone, and sandstone found in the desert mountains as building materials. Oil is produced in the north. The name Arabian Desert is also commonly applied to the desert of the Arabian Peninsula. Image Credit: Nick Leonard 1. Sahara Desert, North Africa The Sahara is the world’s largest desert. At over 9,000,000 square kilometers (3,500,000 sq mi), it covers most of Northern Africa, making it almost as large as the United States or the continent of Europe. The desert stretches from the Red Sea, including parts of the Mediterranean coasts, to the outskirts of the Atlantic Ocean. To the south, it is delimited by the Sahel: a belt of semi-arid tropical savanna that comprises the northern region of central and western Sub-Saharan Africa. Causes of Aridity, and Geography of the Worldï¿½s Deserts Causes of Aridity, and Geography of the Worldï¿½s Deserts Study a physical map of the world.

As you follow the Tropics of Cancer and Capricorn, thirty degrees on either side of the equator, you will see, distributed with suspicious regularity, a brown band of drylands circling the planet, a sere belt warding off greener climes: the deserts of the world. They lie in the so-called Horse Latitudes, where constant high-pressure systems drive away the rain clouds, and swirl above the earth to the music of global temperature variations and the Coriolis Effect produced by the earthï¿½s rotation in space. Most deserts are hot. Within the latitudes of the Tropics of Cancer and Capricorn, the sun appears directly overhead at noon on at least one day of the year. To the north or south of them, the sun is never directly overhead, and not as concentrated as the beam that reaches the tropical areas. Deserts are not scattered haphazardly over the earth; the pattern of their occurrence is shaped by the factors that produced them. The major world deserts occur in these two discontinuous belts ringing the globe. Because more land surface occurs in the Northern Hemisphere in the latitudes described, more deserts occur in the Northern than the Southern Hemisphere.

Not all deserts are hot. Some of these drylands, like the Atacama of Chile, the Namib and Kalahari of southern Africa , and the western Australian desert, are the result of cold oceanic currents that divert rain-laden air away from coastlines. , and the deserts of central and eastern Australia are caused by the ï¿½rainshadow effectï¿½, through which coastal mountains milk rain from the air before it passes inland. and Takla Makan deserts of Mongolia and China , are simply so far away from the ocean that the winds lose any moisture they may hold long before reaching the far off continental interior, even what little moisture remains in the Indian-born clouds after they have scraped over the jagged Himalayas 1.ï¿½ Atmospheric high pressure zones (Hadley Cells) Earthï¿½s atmosphere moves in general, somewhat predictable patterns that are largely driven by the sunï¿½s rays and the earthï¿½s rotation. At the Equator, the sunï¿½s rays are perpendicular with the Earthï¿½s surface; solar heating is intense. Air is heated at the equator, ascends, and is replaced by inrushing air.

As the heated air moves upward, it is gradually cooled. Cool air, with a lower saturation point, is capable of holding less moisture within than warm air. (Equatorial air is very moist). (Oceans cover most of the equator and the high equatorial surface temperature allows large amounts of water to evaporate. So it is not simply warm air that rises at the equator; it is warm, moist air. As the air cools, it releases the excess moisture it contains, helping to produce the moist tropics. i. As the air rises, it cools; the water condenses and precipitation is common. Water returns to the surface as rain. ii. (Deserts do not occur near the Equator, tropics occur there). Higher in the atmosphere, the now cold, dry air rises and moves away from the equator. At about 30 degree latitudes in both hemispheres (north and south), the air descends. As it does, it warms. As it warms, the air expands, condensation and precipitation are infrequent. (Horse latitudes).

To the north and south of these desert latitudes, the air once again ascends, producing moisture for the land; finally, over the poles, the air descends againï¿½ï¿½ Desert formation in these particular latitudes is primarily due to complex global air-circulation patterns caused by the rotation of the earth on its axis (earth moves at great speed near the equator and slowly near the poles), the seasonal tilting of the earth in relation to the sun, and other factors. 2. Continentality or (Distance from oceans) ï¿½ a. Most water in atmosphere is evaporated from the sea, and this water eventually precipitates on land. b. Land closer to the sea generally receives much of this moisture. c. As air moves inland, it gets depleted of moisture and precipitation drops. ï¿½ d. Areas lying deep within a continent may become desert simply because air currents reaching them have already traversed vast land distances; by the time they arrive over the deserts, these currents have already lost the moisture they once carried. e. This is true of some of the Asian deserts., the Gobi , 500 miles inland, receives still less, 11ï¿½ annually.

Coastal Cooling:ï¿½ Deserts may result if air is cooled, and then rewarmed, prior to reaching the region. a. Cool air holds less moisture than warm air. b. When warm, moist air is cooled, excess water condenses and falls as precipitation. If it is subsequently re-warmed, it will be drier than it was previously. 1. Air at 30 C (86 F) can hold 30.4 grams of water per cubic meter (m3). 2. If saturated air (100% relative humidity) was cooled from 30 C to 10 C (50 F), 21 grams of water would condense and precipitate because this cold can only hold 9.4 grams of water per cubic meter. 3. If the air were then re-warmed to 30 C, it would have just a fraction (31%) of the moisture it did originally. 4. (31% relative humidity is fairly dry, and further precipitation is unlikely). 5.

Winds that blow onshore tend to do so across cold currents produced by movement of water from high latitudes (poles) to low latitudes (equator), and associated with the upwelling of cold waters from the ocean's depth. 6. Cold or cool winds have relatively small moisture-bearing capacity and, when warmed during their passage over the land, they become stable and, thereby, reinforce the stability produced by the global stability of these latitudes. (Subtropical highs). c. This occurs along coastal areas where there are cold coastal seas ( Baja CA ), and in rain shadows (adiabatic heating and cooling). d. Air moving across the frigid currents is cooled to a low temperature; thus the air holds little moisture when it arrives over land, where it may provide fog or mist, but rarely rain. (Namib and Atacama). 4. Rainshadow effects ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ a. Moisture-laden air encounters a mountain mass and is moved upward. ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ b.

The ascending air is cooled and releases moisture on the windward side of the range. ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ c. Once over the summit, the air descends the lee side of the range, warming as it does so, and hence increasing its evaporative power. ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ d. The windward side of a range may support a heavy well-watered forest, while the leeward side and the area far below it, robbed of moisture, is occupied by a desert or steppe plant community. The rain-shadow effect produced by great mountains can create arid areas in the lee of the mountains even when continentality is not particularly marked, such as in Patagonia Why are deserts hotter than tropics?ï¿½ (Specific heat capacity). 1. Sand and rock heat up much more rapidly than water, and they also lose heat more quickly. a. On a hot summer day in the Sahara , sand and rock can heat up to 170o F). 2.

When a substance is exposed to heat, its surface temperature rises, but different substances heat up at different rates. 3. The amount of heat that must be applied to a substance to make its temperature rise by 1o is called the specific heat capacity (shc) of that substance. a. the specific heat capacity of water at 59 F is 4.19. b. the specific heat capacity of sand and most solid rocks between 68-212 F, is about 0.8. c. This mean it requires more than 5 times more heat energy to raise the temperature of water 1o than to raise the temperature of rock or sand by the same amount. 4. As the sun climbs higher in the sky, the dry ground heats much faster than water, and much faster than the ground would if it were wet. (Its s.h.c. would then be 1.48). 5. Sand and rock heat more quickly than water, and for the same reason, it cools more quickly, also. 6. The ground temperature falls sharply, reaching a minimum shortly before dawn, but the temperature of water falls much more slowly. 7.

Over the ocean in subtropical latitudes, the difference in day and night air temperatures (diurnal temperature range) is about 0.4 F (0.2C). Over the desert at the same latitude the diurnal temperature range is about 72 F (40C). Sand is a poor conductor of heat (many air spaces), as is air.ï¿½ Radiant heat raises the surface temperature, but heat is not conducted very far below the surface. The upper, heated layer gets continually hotter, while just below the surface the temperature changes very little. Some heat is conducted below the surface, but at a very slow rate. Heat reaches a certain depth before the daily peak temperature is passed. Beyond this depth, the temperature does not alter. This is called the damping depth. ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ In dry sand it is about 3ï¿½ (7.6 cm) below the surface. Because heat penetrates so slowly, the peak temperature is reached at the damping depth several hours later than it is reached at the surface. Microclimates 1.

Conditions (climates) below ground are very different from those at the surface. 2. A local climate of this type is called a microclimate, within the macroclimate of the region as a whole. a. Many living organisms exploit the advantages afforded by microclimates. 3. The subsurface climate is not the only desert microclimate. a. Hollows that are shaded most of the time are cooler than exposed, sun-lit surfaces b. Shelter from (or exposure to) prevailing winds can also create microclimates. c. Above ground air is much cooler than surfaces of sand or rack. At a height of 6.5ï¿½ (2m) the midday temperature may be 55 F (30 C) lower than the temperature at ground level. 4. Fertile islands Desert Geography Study a physical map of the world. As you follow the Tropics of Cancer and Capricorn, thirty degrees on either side of the equator, you will see, distributed with suspicious regularity, a brown band of drylands circling the planet, a sere belt warding off greener climes: the deserts of the world.

They lie in the so-called Horse Latitudes, where constant high-pressure systems separate the westerlies and trade winds, driving away the rain clouds, swirling above the earth to the music of global temperature variations and the Coriolis effect produced by the earthï¿½s rotation in space. Some of these drylands, like the Atacama of Chile, the Namib and Kalahari of southern Africa , and the western Australian desert, are the result of cold oceanic currents that divert rain-laden air away from coastlines. Others, like the Mojave and Sonoran of the American southwest, and Mexico are caused by the ï¿½rainshadow effectï¿½, through which coastal mountains milk rain from the air before it passes inland. Mountains , an extinct volcano, rises to 10,712ï¿½ (3,265m). 5. At various times what is now desert lay beneath ancient seas. This led to a deposition of sand and calcareous deposits that now form sandstone and limestone. 6. Sahara is a hot desert, with summer daytime temperatures exceeding 90F for 8 months of the year, and often exceeding 100F. a.

The high temperature record, recorded at Al-Aziziya in northern Libya , reached 1236.4F (58C). b. At night the temperatures drop sharply, by as much as 50F: nights can be cold and temperatures often fall below freezing in winter. c. Precipitation ï¿½ rainfall is sparse, <2ï¿½ per year. 7. There are 3 types of lands surfaces in the Sahara : erg, reg, and hammada. a. erg ï¿½ ï¿½sand seasï¿½, composed of dunes that have formed basins and depressions from the sand carried into them by rivers of earlier times. i. The large area of dunes are in the northern Sahara Egypt . ii. Surface temperatures can reach 180 F (85C) Air heated by contact with the surface expands and rises. This produces an area of low pressure near ground level. Denser air rushes in to compensate and its movement causes strong, gusty winds. These are called thermal winds because they are caused by temperature differences. b. Reg ï¿½ name given to ground covered by boulders and gravel.

The reg is fairly level, and the areas are generally bleak, windswept, and monotonous. i. Reg is formed by wind action. Small particles are blown from around and between the larger, heavier stones, in a process called ï¿½deflationï¿½. ii. The wind keeps the surface clean, and the finest particles are carried very long distances: Saharan dust has been identified in the United States . c. Hammada ï¿½ is the rocky desert. i. No sand or small particles on the surface ï¿½ just rock, either as large boulders or bedrock. ii. Hammadas are found in northern Libya , and there resembles a vast and uneven parking lot. Probably the most inhospitable type of desert surface. Very little can live on it. 8. Vegetative cover very sparse. a. Susceptibility to wind erosion is very high, b. Water infiltration rates are good, depressions fill with saline water. c. Herbs, small shrubs,with larger shrubs and trees where moisture is abundant (oases). d. Succulents not common. Iran ); a.

An empty quarter in the southern part of the desert is too hot and dry even for desert nomads (similar to the Sahara i. Includes the largest sand desert in the world (south of Najd ), called the Rubï¿½ al-Khali (the empty quarter), covering 230,000 square miles (595,700 sq kilometers). ii. Despite its name, it includes many watering holes and, is therefore, ï¿½crossableï¿½ to those familiar with the desert. b. Arid or extremely arid, < 4ï¿½ per year. a. Hot desert, averaging between 100-107 F from May-Sept. b. ï¿½Most of the plants are annuals; most of the perennials are halophytes. The Saharan and Arabian deserts lie mainly within the Tropics. They are hot deserts produced by descending air on the poleward side of Hadley cells, producing a belt of fairly permanent high pressure. Farther north, the deserts of Central Asia are also caused by persistent high pressure, but they are well-clear of the Tropics and much cooler. South Africa . 2.

Very dry (much drier than its inland neighboring desert, the Kalahari), but not too hot because of coastal fog. 3. High humidity and fog (like Atacama), with less than 2ï¿½ (51 mm) annual precipitation. 4. Very little vegetation: Lichens on the leeward side of rocks, leafless, stem-succulent plants, and halophytes. 5. The Benguela Current, is a cold current that flows northward along the coast. It flows from the edge of the Antarctic Ocean as a stream of water blown in an easterly direction by the West Wind Drift and turning north just south of the southern African continent. 6. Despite having crossed the ocean, winds and air bring no rain because it was chilled as it crossed the cold water of the Benguela Current and its water condensed. It condenses as low clouds and fog, rather than rain and fog. ï¿½ covers an area of about 275,000 sq. miles (712,250 sq. kilometers). 1. Inland desert from the Namib; southwestern Botswana 2. Notable for its deep subsurface sands. 3.

Landscape dominated by gentle dunes. 4. Precipitation in the northern Kalahari reaches 25ï¿½ annually; precipitation in the southern Kalahari, 10ï¿½ annually. 5. The rate of evaporation is high enough to remove much of the surface water before it can be absorbed by the ground. 6. Temperatures range from 90F (32C) in summer to 70 F (21C) in winter, but frosts are common in winter nights. ï¿½ 140,000 sq miles (363,000 sq kilometers) in northern Chile . The Tropic of Capricorn passes thru its center. 1. Narrow strip, 600 miles along (parallel to) coast of Chile . 2. World's driest coastal desert; 0.04" (10 mm) precipitation; most of it from coastal condensation (fog). Rain can be expected no more than 2-4 times per century. Rain is rare, but the relative humidity is 75% - bare iron rust rapidly there. 3.

Coastal cooling: Air reaching the coast from the ocean loses most of its moisture at sea, where it is chilled. It is dry when arrives on land. Any remaining moisture is lost as the air rises to cross the coastal ranges, forming clouds that rarely bring rain, although may be low enough to be calledï¿½ fog. 4. Air from the southwest crosses South American continent, then loses the moisture it carries during its ascent over the Andes Mountains . The combination of coastal cooling from the west, and rainshadow from the southwest accounts for the extreme aridity of the Atacama. 5. Average elevation is about 2,000ï¿½; its height contributing to its moderate temperature. 6. A cool (little seasonal variation ï¿½ about 65 F), very dry climate in a coastal region suggests the presence of a cool ocean current. South America fought over part of the Atacama Desert . The War of the pacific lasted from 1879-1884, and ended with Chile in control of the area, and made Bolivia i. The desert has rich deposits of sodium nitrate and copper. ii. Sodium nitrate is the raw material for commercial fertilizer and explosive manufacture.

ï¿½ occupying the whole of Argentina ; 300,000 sq miles (770,000 sq kilomteres) 1. Cold, rainshadow desert, average annual temperature is 7C. 2. Average rainfall < 10ï¿½ annually. 3. There is no other desert in the world lying on the eastern side of the continent in a latitude north of 40d S. 4. Highest precipitation in the winter, April - Aug. 5. Bleak desert, but in the north there are tough grasses and shrubs; the grasses providing pasture for sheep. 6. Little vegetation farther south, where climate is colder and drier. 1. The Tropic of Capricorn passes thru the center of Australia . This means the country lies close enough to trade wind latitudes for the prevailing windsï¿½ to be from the southeast. These bring maritime conditions, with abundant rain, to the coast of New South Wales Queensland . 2. Inland lies the Great Dividing Range, a mountain range running the length of the country parallel to the east coast. 3. Lands to the west of the mountains lie in a rain shadow. 4.

40% of Australia ï¿½s land mass is classified as desert (3.4 million square miles). Of all the continents, Australia Australia is alarge island with a continental climate). 5. No succulents, very few spiny plants. Prevalent desert plants are the perenial evergreen tussock grasses (spinifex) and small trees or shrubs belonging to the genus Acacia. 6. has 5 deserts: 4 on the west side, one in the center. a. ï¿½ southeast corner of the Northern Territories ; < 500ï¿½ asl; stony desert b. Great ï¿½ north part of western Australia ; < 600ï¿½ above sea level. c. Great South Africa: Major Landforms Major Landforms -covers 1/3 of the whole continent -largest desert in the world -almost as large as the United States -approximately 3,500,000 sq.

miles -Rock-strew plains, rolling sand dunes, many sand seas -regional deserts are the Libyan, Nubian and Western desert of Egypt -all deserts lie west of the Nile • Kalahari desert -covers the southwestern region of South Africa and all of western Namibia -approximately 100,000 sq. miles -lies between the Orange and Zambezi rivers -consists of dry lake beds -Yearly rainfall averages about 5 in. in the southwest where there are active sand dunes and 20 in.

of rainfall in the northeast -can rain heavily one day, then be dry as ever the next -grazing and agriculture is possible in certain areas -popular tourist spot for the Kgalagadi Transfrontier park -considered one of Africa’s last “wildlife paradises” -includes meerkats, hyenas, lions, many species of antelope, birds, reptiles -first inhabitants of Kalahari are called the the “San” or “bushmen” -today, only a small amount of bushmen follow traditional ways of living -modern civilizations threaten natural resources -coal, copper and nickel deposits were discovered by mineral companies • Congo River -also known as “the Zaire” -dominates the landscape of the Democratic Republic of the Congo and Congo -flows into Angola, Cameroon and the Central African Republic and Zambia -approximately 1,400,000 sq.

miles -second longest river in Africa -fifth longest river in the world -discharge of 1,500,000 cubic feet of water per second -consists of freshwater fish that is an important source of protein for the people of central Africa -best known as a mystical land of mythical beasts, plagues and cannibals -called “the heart of darkness” by Joseph Conrad • Atlas Mountains -located in Tunisia and Morocco -approximately 1,500 miles -provides a route between the coast and the Sahara Desert -lies in northwestern Africa -highest range found in the southern part of Morocco is called the High Atlas -highest peak is found in central Morocco which is 11,000 feet -slopes of the High and Middle atlas have dense forests that include cedar, cork, pine, oak trees -fertile valleys -tracts of land where livestock feed -wide range of mineral deposits that have been rarely touched -lead, zinc, manganese, iron, antimony, phosphates, gold, silver -traditionally considered as Berber territory • Great Rift Valley -approximately 4,000 miles in length -expand from the Red Sea area to the South African country of Mozambique -cent

uries ago, volcanic eruptions caused chain of geological faults which later created what we call now the Ethiopian Highlands -also created chains of mountain ridges, perpendicular cliffs, deep lakes, rugged valleys -Africa’s highest mountains – Mt.

Kilimanjaro, Mt. Kenya and Mt. Margherita all front rift valley -rich source of human fossils that allow the study of human evolution -bones of hominid (apes) ancestors from modern humans are found • Nile River -longest river in the world -runs about 4,160 miles in length -drains in the Mediterranean sea -series of streams, dams, swamps, waterfalls and rapids -made of major rivers – Albert, Blue, Victoria and White Nile -average discharge is about 300 million cubic meters per day -farming, tourism and fishing happens on the Nile River -you will see traditional Egyptian sailing boats/luxury cruisers traveling up and down -hundreds of farms along the river, farmers use boats to transfer wheat, cattle, hay, etc.

-fishing is a main source of income and wealth, tons of fish are caught each year • Sahel -wide range of land that runs across north-central Africa on the southern edges of the Sahara Desert -it is the transition zone between tropical places of the south and dry places of the north -receives very little rain, 6-8 inches a year -most of the land is a growth of grasses and shrubs -approximately 2,400 miles -mainly flat, most of the region lies between 200-400 meters elevation -home to large populations of endangered mammals -several kinds of gazelles, cheetahs, lions, African wild dogs, etc. By Cherry

Question: What desert lies to the south of Fukah
Answer: The Sahara