1 hrly gs ch 05 deserts

Deserts

Desert

Definition:– Desert is a place which receives very little rain,

and have an evaporation rate that exceeds precipitation

• Receives less than 10 inches (25 cm) a year– Although the amount varies from year to

year

• Deserts cover about 20% of the surface of the Earth

• They are found on every continent.

• Desert have a large temperature variance– Daytime 55OC– Nighttime Freezing cold at night

• Consists of distinctive and specialized vegetations and animals

• Few large mammals in the deserts – Because they are not capable of

storing sufficient water and withstanding the heat

• Yet more than one billion people, one-sixth of the Earth's population, actually live in desert regions

Types of Deserts

• Following are the major classifications of desert:– Cold desert

• Polar desert• Tundra or Temperate desert

– Hot desert Arid desert– Coastal desert

Cold Deserts

Polar

Tundra

• Also known as Arctic Tundra

• Located near the polar regions

• These deserts are covered with snow and ice

• They have extremely cold temperatures year-round– A cold desert never rises above

10 oC in the summertime

Pola

r D

esert

• Instead of sand dunes, there are snow dunes

• Following are Polar deserts:– Antarctic Largest– Arctic Second largest– Greenland desert– Nearctic Realm

• Northern Canada• Northern Russia

Antarctic

Arctic

Tu

nd

ra

Desert

• Also known as Alpine Tundra

• Located at higher altitudes on mountains where trees do not grow

• Climate– Summers Hot and dry

– Winter Brutally cold, dry winters with temperatures far below the freezing point

• Characteristics– It is often treeless

• The snow underground makes it difficult or impossible for trees to root down into the ground

– Receives little precipitation

– Reaches extremely frigid temperatures, especially in the winter when it receives little to no sunlight

• Following are few tundra deserts:– Gobi desert Asia– Kyzyl Kum desert Asia– Taklamakan desert Asia– The Great Basin Desert North

America– Patagonian Desert South

America– Karakum Desert Asia – Dasht-e Kavir Asia

• Animals that live in cold deserts have special adaptations:

An

imals

livin

g in

Cold

D

esert

– Polar Bear– Walrus– Arctic Wolf– Arctic Hare– Emperor

Penguins

– Rock Ptarmigan – Caribou or Reindeer– Musk Ox– Arctic Ground Squirrel– Least Weasel– Arctic Wolverine– Yak– Harp Seal– Blue Whale

Penguin

Polar Bear

Walrus

Seal

Arctic Wolf

Arctic Hare

Rock Ptarmig

an

Arctic Ground Squirrel

Caribou

Arctic Lemmin

g

Arctic Wolveri

ne

Arctic Lemmin

g

Musk Ox

Yak

White Siberian

Tiger

Siberian Tiger

Husky Sled Dogs

Hot Desert

• A true desert climate

• Covers 12 % of the Earth's land surface

• Located at low altitudes

• Soil nature Saline or Alkaline

Ari

d D

esert

• Topography – Sand dunes – Rocks

• Hot and dry all year round– Because receive very little rainfall– High evaporation rate compared

to rainfall Rainfall evaporates before it reaches the ground

• Temperature Exhibit extremes– Day Very hot

• Because no clouds to shield the earth from the sun's rays

• The atmosphere contains little humidity to block the rays of the sun.

– Night Very cold – Drop below freezing

• Following are some hot deserts:– Sahara Desert Asia– Arabian Peninsula Asia– Great Sandy Desert Australia– Kalahari Africa– Syrian Desert Asia

• Adaptations to cope with the lack of water and the extreme temperatures – To avoid daytime heat

• Nocturnal animals • Burrow beneath the surface • Hide in the shade during the day

– Desert animals drink no or very little water• Get all the water they need from their

food• Most animals are small

• Physiological adaptations:– Aestivation (dormancy during

summer)– The absence of sweat glands– Localized deposits of fat in tails or

humps– Reptiles with their waterproof

skin

• Animals that live in hot deserts:– Desert Bighorn Sheep – Kangaroo Rat– Scorpion– Coyote– Tarantula– Camel– Greater Roadrunner– Addax Antelope – Ibex– Egyptian Vulture – Dingo

Bighorn Sheep

Kangaroo Rat

Desert Scorpion

Tarantula

Addax Antelope

Ibex

Coyote

Mountain Lion

Egyptian Vulture

Great Roadrunn

er

• Only specialized plants can survive in these deserts which have few of the following characteristics:

– Vegetation consists mainly of shrubs and small trees

– Reduction of leaves Spines

– Those which have leaves, retain water

– Extensive underground root systems• Grow straight down to groundwater• Spread out extensively under the

surface of the desert  – Elimination of competitors' roots

by injecting toxic chemicals into the soil known as allelopathy

• Following are few of the plants:– Cactus– Date– Prickly Pears – False Mesquite – Turpentine Bush– Yucca Plant– Ocotillo– Agave Plant– Brittlebush

Cactus

Date Palm

False Mesquite

Prickly Pears

Yucca Plant

Agave Plant

• These deserts are dry but not hot– Because of frigid ocean currents

• Seasons– Summers

• Warm and mild• Longer than winters

– Winters • Cool• Shorter than summers

Coasta

l D

esert

• Following are twp coastal deserts:– Atacama, Chile South America– Namib Africa

• Not as harsh as the hot and dry deserts– More types of animals can live

here

• Vegetations:– Black sage – Rice grass – Salt bush