The second-largest desert is the Arctic Polar Desert. It has a surface area of about 5. The Canada Glacier is in the background. The rest of Earth's deserts are outside of the polar areas. The largest is the Sahara Desert, a subtropical desert in northern Africa. It covers a surface area of about 3. A list of more than twenty of the largest non-polar deserts can be found below. When most people think of a desert, they imagine a landscape covered with sand and sand dunes.
Although many deserts are sand-covered, most are not. Many desert landscapes are rocky surfaces. They are rocky because any sand-size or smaller particles on the surface are quickly blown away. Rocky deserts are barren wind-swept landscapes. Most deserts receive so little precipitation that surface streams usually only flow immediately after rainfall - unless the stream has a source of water outside of the desert.
Streams that enter a desert usually suffer major water losses before they exit. Some of the water is lost to evaporation. Some is lost to transpiration taken up by plants and then released to the atmosphere from the plants. The third-largest desert in the world and the largest non-polar desert is the Sahara. The Arabian Desert is the fourth largest desert in the world, with an area of about , square miles. Both the Sahara and Arabian Deserts are known for their sand and dunes, which are typical images of desert landscapes.
Situated in northwestern China and southern Mongolia, the Gobi Desert was created as a rain shadow from the tall Himalayan Mountains, which prevent rain from reaching the Gobi. The Kalahari Desert ranks sixth in terms of largest deserts by area in the world. The Great Victoria Desert is next on the list, ranking eighth. It spans about , square miles of Australia. The plant life in the Sahara is sparse, due to the harsh climatic conditions. Approximately plant species are known to grow in the region.
Plants must be able to adapt to hot and dry conditions, or able to live in areas with salt water. Given the immensity of the desert, the biodiversity is remarkably low.
Acacia trees, grasses, spiny shrubs, and palms, for example, have adapted to the Saharan climate by growing closer to the ground to avoid water loss from strong winds. They can also store moisture in their stems and have roots that branch out horizontally to maximize the area they cover for moisture collection.
Thick leaves and needles prevent evaporation. Along the Atlantic coast, there is enough moisture to sustain plants like lichens, succulents, and shrubs. In the highlands of the Tibesti Mountains and Jebel Unweinat Mountains, rainfall is more plentiful and temperatures are lower, so plants such as tamarix, myrtle, oleander, acacias, and palms can be found in the woodlands. Approximately 70 different animal species live in the Sahara. Mammal species include those that can survive for an extended period without water intake, such as the fennec fox, pale fox, African wild dog, Saharan cheetah, and the dorcas gazelle.
The addax, a species of white antelope, is known to survive for as long as a year without drinking water. Several species of lizards, snakes, and scorpions also live in the desert. There are even desert crocodiles in parts of Mauritania and Chad. Saharan birds include the African silverbill and the black-throated Firefinch. The Berbers still inhabit much of the Sahara, and the only domesticated animals seen in the desert are camels and goats. The hot, dry climate of the Sahara is especially harsh.
Because the air contains very little humidity to hold the heat in, there is a great difference between daytime and nighttime temperatures. At night, the temperature regularly falls below freezing. In terms of rainfall, about half of the Sahara receives less than 0.
A strong wind called the Sirroco originates in the Sahara. Winds may be as strong as 62 miles per hour km and are responsible for the hot and dry climate in Northern Africa. In fact, sand storms in the Sahara can be so big that they are visible from outer space! It is no surprise therefore that this desert has much in common with the Sahara desert and its sands have the same orange colouration due to the presence of iron […].
Interesting adjunct to that: 6 million years ago the mediteranean was nothing but salt lakes and marshes. That lasted until around , yrs ago. Then right down French Equatorial Africa.
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