In this lesson, you'll learn about:
Deserts are typically areas that receive extremely low amounts of rain. They generally get 10 inches or less rain in a year. Around one-third of the Earth’s surface is covered in desert. The original meaning of the word desert is ‘an abandoned place’. They are characterized by an overall lack of water. They have dry soil, little to no surface water, and high evaporation. Big mountains like piles of sand that get collected in a desert are called sand dunes.
Sand dunes
Deserts are extremely dry with very low humidity. They have no “blanket” to help insulate the ground. As a result, they get very hot during the day but can get quickly cold once the sun sets in. Some deserts can reach temperatures of well over 100°F during the day and then drop below freezing (32°F) during the night.
Although most deserts such as the Sahara of North Africa and the deserts of the southwestern US, Mexico, and Australia, occur at low latitudes, another kind of desert, cold deserts, occur in the basin and range area of Utah and Nevada and in parts of western Asia. The desert biome can be found on every continent except Europe.
Desert that receives rain as the main form of precipitation is called hot deserts while those which receive snow as their main form of precipitation are called cold deserts. Many of the ice-free regions of the Arctic and Antarctica are known as polar deserts. Only around 20% of the deserts on Earth are covered in sand.
The largest cold desert on Earth is Antarctica. The largest hot desert on Earth is the Sahara. It covers over 300 million square miles. The Sahara Desert is located in northern Africa, spanning 12 different countries. The Arabian Desert in the Middle East is the second-largest hot desert on Earth. Other large deserts include the Gobi Desert in Asia, the Kalahari Desert in Africa, the Patagonian Desert in South America, the Great Victoria Desert in Australia, the Syrian Desert in the Middle East, and the Great Basin Desert in North America.
Hot Desert versus Cold Desert
| Hot Desert | Cold Desert |
| It refers to a desert with an extremely hot climate. | It refers to a desert with an extremely cold climate. |
| Has a high temperature. | Has a low temperature. |
| Hot deserts are found in the tropical and sub-tropical regions (western coasts of continents). | Cold deserts are mostly found in temperate regions at higher latitudes. |
| It has high sun and sandy soil. | It has ice and snow on the ground. |
| It is red or orange in color. | It is gray in color. |
| Precipitation levels are generally lower than in cold deserts. | They tend to have higher precipitation levels than hot deserts. |
| Evaporation is higher than precipitation. | Precipitation is higher than evaporation. |
| Situated at the Tropic of Cancer and Tropic of Capricorn. | Situated north of the Tropic of Cancer and south of the Tropic of Capricorn. |
| Commonly found animals include fennec foxes, camels, snakes, coyotes, etc. | Commonly found animals include polar bears, deer, jackrabbits, kangaroo rats, pocket mice, badgers, etc. |
| Vegetation is very rare and mostly includes ground-hugging shrubs and short woody trees. | Vegetation is scattered with needle-like leaves. |
| Example: Sahara, Arabian, Thar, Kalahari. | Examples: Antarctic, Greenland, Iran, Turkestan, Northern, and Western China. |
Desert biomes can be classified according to several characteristics. There are four major types of deserts:
1. Subtropical Deserts - Subtropical deserts are hot and dry year-round. These are the hottest deserts. They are found in Asia, Australia, Africa, and North and South America. Subtropical deserts are very hot and dry in the summer and cooler but still dry in the winter. Rainfall happens in short bursts. The air is so hot and dry in these deserts that sometimes rain evaporates before it even has a chance to hit the ground. The soil in subtropical deserts is usually either sandy or coarse and rocky.
Plants and animals in subtropical deserts must be able to withstand the hot temperatures and lack of moisture. Shrubs and small trees in the subtropical desert usually have leaves adapted to retain moisture. Animals in subtropical deserts are usually active at night when it is cooler.
2. Coastal Deserts – Coastal deserts occur in cool to warm areas along the coast. They have cool winters and long, warm summers. Coastal deserts are located on the west coasts of continents between 20° and 30° latitude. Winds off the coast blow in an easterly pattern and prevent the moisture from moving onto the land. The Namib Desert in Africa and the Atacama Desert in Chile are coastal deserts.
3. Cold Winter Deserts – Cold winter deserts are also known as semi-arid deserts. They have long, dry summers and cold winters with low rain or snowfall. In the United States, the Great Basin, the Colorado Plateau, and the Red Desert are all cold winter deserts. Other cold winter deserts include the Gobi desert in China and Mongolia and the Patagonian Desert in Argentina. The lack of rainfall in cold winter deserts is often caused by the rain shadow effect. The rain shadow effect happens when a high mountain range stops moisture from reaching an area. The Himalayan Mountains prevent rainfall from reaching the Gobi Desert.
4. Polar Deserts – Polar desert is found in the Arctic and Antarctica regions. Like warmer deserts, they also get very little precipitation. Despite the extreme conditions, deserts are home to a range of well-suited plant and animal life.
Only certain types of plants can survive the harsh environment of the desert. These include cacti, grasses, shrubs, and some short trees. You won’t see a lot of tall trees in the desert. Most of these plants have a way to store water in their stems, leaves, or trunks so they can survive a long time without water. They also tend to spread out from each other and have a large root system so they can gather up all the water possible when it does rain. Many desert plants are armed with sharp spines and needles to help protect them from animals.
Animals have adapted to survive in the desert despite its extreme temperatures and lack of water. Many of the animals are nocturnal – they sleep during the heat of the day and come out when it is cooler at night. These animals sleep in burrows, and tunnels under the ground, during the day in order to stay cool. Desert animals include meerkats, camels, and reptiles such as the homed toad, scorpions, and grasshoppers.
Animals that live in the desert also have adapted to needing little water. Many get all the water they need from the food they eat. Other animals store up water that they can use later. The camel stores up fat in its hump while other animals store up reserves in their tails.
Because the desert is so dry, the wind will grind pebbles and sand into dust. Occasionally, a big wind storm will gather up this dust into a huge storm. Dust storms occur when the wind picks up dust from the surface. Dust storms can be over 1 mile high and so thick with dust you can’t breathe. They can travel for over a thousand miles, too.
The desert area in the world is getting bigger. Desertification is the expansion of the desert into the surrounding areas. It usually happens on the edge of deserts and is caused by a variety of factors. There are many causes of deserts spreading:
Desertification is a significant global ecological and environmental problem. The main regions currently threatened by desertification are the Sahel region lying to the south of the Sahara desert in Africa, parts of eastern, southern, and northwestern Africa, and large areas of Australia, south-central Asia, and central North America.
Drylands occupy approximately 40-41% of Earth's land area and are home to more than 2 billion people. It has been estimated that some 10-20% of drylands are already degraded, the total area affected by desertification being between 6 and 12 million square kilometers, that about 1-6% of the inhabitants of drylands live in desertified areas, and that a billion people are under threat from further desertification.
Effects of desertification
In 1977 the worldwide consequences of desertification were the subject of a United Nations Conference on Desertification
What actions can be taken to prevent desertification?
