Deserts
A desert is a hot area of land that gets very little rain—not more than 200 mm a year. Temperatures during the daytime can get as high as 55° C. At night, deserts cool down, sometimes even below 0° C.
Deserts cover about 20% of the world’s land. The biggest is the Sahara desert, which is about the same size as Europe.
Because deserts are very dry only certain kinds of plants and animals can live there.
Locations of deserts
Most deserts lie between 15° and 35° north and south of the equator. They were created by air that rises over the equator and comes down over the Tropic of Cancer and the Tropic of Capricorn . All over the world many deserts lie in these regions.
- Land over the equator becomes very hot. The hot and wet air rises and it rains a lot in these areas.
- The air cools down and moves north– and southwards. It gets drier.
- The cool air sinks to the ground. It dries out over the Tropic of Cancer in the north and the Tropic of Capricorn in the south.
- Warm air near the surface moves back to the equator. These winds are called trade winds .
Some deserts are formed in regions that are cut off from the ocean by high mountains. Winds carry wet air from the ocean to the land. When the air climbs over high mountains it loses most of its moisture and when it falls down on the other side it becomes very warm and dry. Deserts on the western coast of North America were formed by such winds.
Many areas have become dry because they are too far away from the ocean. Air loses its moisture by the time it reaches places that are thousands of kilometres from the coast.
Deserts can also develop near the coast. Cold water moves from the Antarctic northwards along the African and South American coast. The warm air in these places cools down and mixes with the cool water. There is a lot of fog , but no rain. That’s why the Atacama desert in Chile and the Namib desert in Africa are among the driest deserts in the world.
Landscapes of the desert
Only about 10% of all deserts are made up of sand. Most of them are rocky places that consist of gravel and larger stones. Desert landscapes are formed mostly by the power of the wind and water.
Strong winds form rocks in strange ways. They also build up dunes made of sand. Such dunes can be up to 200 m tall and they can travel large distances every year.
After rainy times, small streams carry water. They cut their paths through the desert and carry sediments with them .These streams often end in lakes where the water evaporates and salt and minerals are left over.
Sometimes underground water comes to the surface . Such a place is called an oasis . It is the only spot where people can live, plant crops and raise animals.
Climate of Deserts
In summer, temperatures may reach up to 55°C during the daytime , but at night they drop below 0° C.
Most deserts get very little rainfall— on average , not more than 20 cm a year. There may be years without any rainfall at all. Sometimes a lot of rain falls during thunderstorms that last for a few hours.
When the desert dries up after heavy rainfall, salt and other minerals are left behind on the ground. Salt lakes are very common in these places. That is why some desert areas have yellow, brown and red colours.
Living in the desert
People who live in deserts must protect themselves from high temperatures during the daytime and low temperatures at night and in the winter.
Some people live in mud houses that are painted white . They keep out the heat during the daytime and protect people from cold evenings. Nomads in Africa live in tents and move around all year in search of areas with water. Many of them wear long coats that protect them from the sun and the wind.
Plant life
Desert plants must change their way of life and get used to the heat and the dryness .
Some flowers only live for a few days . The seeds may be in the desert ground for years and when it rains they start to blossom .
Plants of the desert usually have small leaves that look like needles . Such plants can live with very little water, which they store in the needles or stems . Some plants have long roots that reach up to 80 metres below the surface .
Animals
Many kinds of animals live in the desert: spiders, reptiles , birds and some mammals .
Most animals stay in the shade during the daytime and look for food at night when it gets cooler. They get water from the food they eat or from the water holes in the desert. Some animals sleep during the summer.
Camels are animals that are fit to live in the desert. They can go on for days without drinking water and need only little to eat. They carry their food in their humps . They also give nomads wool and tents are made out of their skin.
The Sahara - The biggest desert in the world
The Sahara is the biggest desert in the world . The landscape is made up of mountain ranges , rocky plateaus and sandy plains called ergs. The Nile is the only river that carries water all year long. It flows through the Sahara in Sudan and Egypt.
The desert reaches from the Atlantic Ocean in the west to the Red Sea in the east –over 3,500 km. The highest peaks are in the Tibesti mountains . They reach a height of about 3,500 metres.
There are about 90 bigger oases in the Sahara desert, where water comes up from underground rivers or wells . People here live in small villages and grow crops.
The Sahara also has important raw materials . Oil and gas lie under the Algerian and Libyan desert. There are also other minerals, like copper and iron ore .
About 2 million people live in the desert. Most of them are Arabs or Berbers . The Tuareg are a tribe that live in the mountainous areas of the central Sahara. Most of them are nomads who raise sheep , goats or camels and travel around all year.
In desert oases people can live the whole year. They grow dates , wheat and other crops . But, they must also fight against sand storms and wandering dunes that threaten to cover the oases with sand.
The Sahara was not always a desert. During the Ice Age , when many parts of the world were covered with snow and ice, northern Africa had a much wetter climate. The Sahara had many lakes and rivers and elephants and giraffes lived in the grasslands and forests. At about 5000 BC the climate started to become drier and the Sahara turned into a desert. Many people moved south.
Today the desert is growing because people destroy fertile land. They raise too many animals that eat all the grass or they cut down trees that still exist.
Downloadable PDF Text- and Worksheets
Related Topics
Words
- among =together with
- average =normal, usual
- BC = Before Christ
- Berber = people who live in Northern Africa
- blossom = to produce flowers
- carry = to take with it
- certain =special
- common = you can find something very often
- consist of =to be made up of
- copper = a metal that shines yellow and brown
- cover =to spread over
- create = make
- crops =a plant like wheat or corn that farmers grow for food
- cut =hack, chop
- cut off =separate
- date = a sweet, sticky brown fruit with a long hard stone inside
- destroy =damage completely, ruin
- develop =build up
- distance =the area from one place to another
- drop = go down
- dryness =the situation of being dry, without any water
- dune = a hill made of sand
- evaporate = water changes into gas
- fertile =good, productive
- fit =good enough; the right ones
- fog = cloudy air near the ground. It is difficult to see through it
- get used to =here: to be in a new place so long that you can live there without any problems
- gravel = small stones
- heat =high temperatures
- heavy = very strong
- height =how high something is
- hump = the high part of a camel
- in search of = to look for
- iron ore =rock from which you can make iron
- landscape =an area or countryside of a special type
- little = not very much
- lose = it doesn’t have something any more
- mammal = an animal that drinks milk from its mother’s body when it is young
- moisture = small parts of water that exist in the air or on the ground
- mountain range = a group of mountains
- mud = wet earth that is soft and sticky
- needle =special kind of leaf that is very sharp
- nomad = a person who travels from place to place to find grass and water for animals
- northwards = to the north
- oasis = a place with water and trees in a desert
- path = way
- peak = the sharp top of a mountain
- plains = a large area of flat land
- plant crops =to grow plants like wheat or corn which farmers use as food
- plateau = a large area of flat land that is higher than the land around it
- protect =defend , guard
- raise = to look after animals
- raw material =things that exist in nature and which we use every day, like coal, oil, water
- reptile = an animal that changes its body temperature, like a snake
- rise = go up
- rocky =stony, full of rocks
- root = the part of a plant or a tree that grows under the ground and gets water there
- sediment = small stones and sand that rivers carry with them
- seed = a small hard object of a plant. A new plant can grow from this
- shade = out of the sunlight
- spot = place, area
- stem = the long, thin part of a plant
- store = to put away until you need it
- stream = a very small river
- surface =the top layer of an object
- tent =a shelter you put up when you go camping; it is covered with cloth and you hang it to the ground with ropes and poles
- threaten =endanger, put at risk
- thunderstorm = a storm with thunder and lightning
- trade wind = a tropical wind that blows to the equator from the northeast or the southeast
- tribe = a group of people who have the same skin colour, language and religion. They live in a small area
- Tropic of Cancer = a line around the world that lies 23 ½ ° north of the equator
- Tropic of Capricorn = a line around the world that lies 23 ½ ° south of the equator
- wandering dunes = mountains of sand that move from one place to another
- water holes = a small place where animals drink
- well = a deep hole in the ground that has water in it
- wheat =a plant that you make white bread from
- wool = the soft thick hair of some animals