A desert is defined as a barren area that receives little precipitation, making living conditions difficult for organisms. About one-third of the Earth's land is arid or semi-arid, including polar regions called "cold deserts". Deserts can be classified by factors like precipitation, temperature, causes of desertification, and location. Plants and animals in deserts have adaptations like small leaves, spines, staying underground or dormant to survive the harsh environment. The Atacama Desert in Chile is one of the driest places on Earth, with some weather stations never receiving rain.

2. DEFINITION
A desert is a barren area of land where little precipitation occurs and
living conditions are hostile for human, plant and animal life.

3. DENUDATION
The lack of vegetation exposes the unprotected surface of the ground
to the processes of denudation.

4. ARID AND SEMI-ARID REGIONS
About one third of the land surface of the world is arid or semi-arid.
This includes much of the polar regions where little precipitation occurs
and which are sometimes called "cold deserts".

5. DESERT CLASSIFICATION
Deserts can be classified by:
• the amount of precipitation that falls
• the temperature that prevails
• the causes of desertification
• their geographical location

6. ROCKS AND WEATHERING
Deserts are formed by weathering processes as large variations in
temperature between day and night put strains on the rocks which
consequently break in pieces.

7. PLANTS
Plants living in the desert need special adaptations to survive in the
harsh environment. Plants tend to be tough and wiry with small or no
leaves, water-resistant cuticles and often spines to deter herbivory.

8. ANIMALS
Animals need to keep cool and find enough food and water to survive.
Many are nocturnal and stay in the shade or underground during the
heat of the day. They are efficient at conserving water. Some animals
remain in a state of dormancy for long periods, ready to become active
again when the rare rains fall. They then reproduce rapidly while
conditions are favorable before returning to dormancy.

9. HUMAN IMPACT
People have struggled to live in deserts and the surrounding semi-arid
lands for millennia. Nomads have moved their flocks and herds to
wherever grazing is available and oases have provided opportunities for
a more settled way of life. Many trade routes have been forged across
deserts, especially across the Sahara Desert, and traditionally were
used by caravans of camels carrying salt, gold, ivory and other goods.
Large numbers of slaves were also taken northwards across the Sahara.

10. ETYMOLOGY (NAME ORIGIN)
The word desert come from the Latin
dēsertum which translates "an
abandoned place“.

11. 10 LARGEST DESERTS IN THE WORLD
1. Antarctic Desert (Antarctica) 14,200,000 km²
2. Arctic Desert (Arctic) 13,900,000 km²
3. Sahara Desert (Africa) 9,100,000 km²
4. Arabian Desert (Middle East) 2,600,000 km²
5. Gobi Desert (Asia) 1,300,000 km²
6. Patagonian Desert (South America) 670,000 km²
7. Great Victoria Desert (Australia) 647,000 km²
8. Kalahari Desert (Africa) 570,000 km²
9. Great Basin Desert (North America) 490,000 km²
10. Syrian Desert (Middle East) 490,000 km²

12. ATACAMA DESERT
One of the driest places on Earth is the Atacama Desert. It is virtually
devoid of life because the average precipitation in the Chilean region
of Antofagasta is just 1 mm per year. Some weather stations in the
Atacama have never received rain. Evidence suggests that the
Atacama may not have had any significant rainfall from 1570 to 1971.
Amazingly there is some plant life in the Atacama, plants that obtain
moisture from dew and the fogs that blow in from the Pacific.