DESERTS

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

DENUDATIONThe lack of vegetation exposes the unprotected surface of the ground to the processes of denudation.

ARID AND SEMI-ARID REGIONSAbout 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".

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

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

PLANTSPlants 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.

ANIMALSAnimals 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.

HUMAN IMPACTPeople 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.

ETYMOLOGY (NAME ORIGIN)The word desert come from the Latin

dēsertum which translates "an abandoned place“.

10 LARGEST DESERTS IN THE WORLD

1. Antarctic Desert (Antarctica) 14,200,000 km² 2. Arctic Desert (Arctic) 13,900,000 km²3. Sahara Desert (Africa) 9,100,000 km²4. Arabian Desert (Middle East) 2,600,000 km²5. Gobi Desert (Asia) 1,300,000 km²6. Patagonian Desert (South America) 670,000 km²7. Great Victoria Desert (Australia) 647,000 km²8. Kalahari Desert (Africa) 570,000 km²9. Great Basin Desert (North America) 490,000 km²10. Syrian Desert (Middle East) 490,000 km²

ATACAMA DESERTOne 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.