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Earth's Deserts: Definition, Distribution & Location

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  • 0:03 What Is a Desert?
  • 2:14 Desert Location in…
  • 3:14 Desert Distribution
  • 4:54 Lesson Summary
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Lesson Transcript
Instructor: Margaret Cunningham

Margaret has taught many Biology and Environmental Science courses and has Master's degrees in Environmental Science and Education.

Imagine a place where rain rarely falls and plants and animals are specially adapted to survive. In this lesson, we'll learn why deserts form and how their location is determined by the atmosphere, the hydrosphere and geology.

What Is a Desert?

Think about all of the different types of habitats you have been to or have seen on television. The earth is covered in many different types of habitats that vary by climate and by the animals and plants that live there.

One very interesting and unique type of habitat is a desert. Deserts are defined as regions with very low rainfall, usually less than 25 centimeters of rain per year. Due to the limited rainfall, deserts often have very dry soil or sand that is easily moved around by wind. This results in a continuously changing landscape.

Although deserts are characteristically dry, in some regions, when it rains, it pours. In many desert regions, it will rain once or twice per year but will dump more than 13 centimeters of rain in a short time period. The landscape cannot absorb the large amount of rain and the result is often a flash flood - when large quantities of water flow over the land for a short period of time.

Another unique characteristic of deserts is the unique organisms and plants that live there. Although at first glimpse a desert may look sparse or abandoned, there is actually a great deal of life present. There are many specialized plants that have developed adaptations that make it possible for them to live in such a harsh and dry climate. These plants survive by storing water in large root systems and by having small, waxy leaves to reduce water loss. A cactus is a great example of a desert plant that has adapted to life with limited water. There are even some plants in the desert that look dead for most of the year, but will become green and flower when it rains!

There are also many animals that live in desert habitats. Similar to plants, these animals have developed adaptations to help them survive. Many desert organisms live in deep, cool burrows underground. They use these burrows to avoid the heat and some even hibernate in the ground during periods of extreme drought. Some desert animals are only active at night when it's cooler. Camels survive life in the desert by drinking large amounts of water when it is available and storing it in their body for later use. Due to this adaptation, some camels can survive for weeks without drinking.

Desert Location in Relation to Atmosphere

The location of deserts is directly related to the atmosphere, which is the combination of the gases that surround the earth. The hydrosphere, which is the water on the earth's surface, is also involved in the creation of deserts. Water from the hydrosphere evaporates and travels into the atmosphere. The air above oceans and lakes is often very moist due to the large amount of water that is in the air. The atmosphere can cause the air and water particles to move around the globe.

The global pattern of air circulation controls where air moves around the planet. If the moist air travels over land near the equator, it will rise, expand and cool, which causes precipitation. Due to the large volume of precipitation that occurs, the air becomes dry as it travels north or south of the equator. This air will later sink, compress and warm and will not be able to form precipitation over the land. Additionally, the dry air will cause increased evaporation, contributing to the formation of a desert.

Desert Distribution

Due to the global pattern of air circulation and the relation to the atmosphere, most deserts are found within a belt centered on the 30° North and 30° South latitude lines. These regions are characterized by having a great deal of sunlight, minimal rain and high levels of evaporation.

Although most deserts are within this latitudinal belt, there are some exceptions. There are deserts found in other regions of the world that are created due to interactions with the land and geological setting. Some deserts are formed within rain shadow zones, which are the downwind sides of mountains that receive limited rainfall. As moist air passes over a mountain range, it often causes precipitation, leaving the air that moves down the other side of the mountain to be void of moisture. This creates a dry habitat.

Some deserts are formed because they are an extreme distance from oceans. Land deep within the interior of a continent receives very dry air that has already lost the majority of its moisture while traveling from a distant ocean. Deserts can also be formed on tropical coasts that receive cold ocean currents. Colder air cannot carry as much moisture as warm air, so when the cold ocean currents cool the air above, the air becomes very dry. When this air reaches land, it causes more evaporation than precipitation, which results in the formation of a desert.

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