Chapter 7Sections 1, 2 & 3

All deserts have one thing in common… very little rainfall.

Rainwater moving through soil carries minerals deeper into the soil through a process called LEACHING

Very little leaching occurs in deserts Upper levels of soil is rich in minerals Not a lot of organic matter = little topsoil

If loose soil is removed, a lower layer of soil, called PAVEMENT is exposed

Pavement is the desert floor The desert floor is made up of hard-baked

sand and/or bare rock particles

Cool Deserts Found on eastern

side of Sierra Nevada and Rocky Mountains

Main plant is the sagebrush

Hot Deserts Found in south

west, particularly Arizona, New Mexico and western Texas

Main plant is the cactus

Desert Climate Rarely get more

than 25 cm of rain per year

Precipitation is the limiting factor of the desert

Most deserts receive less than 10 cm of rain

Hot days and cold nights

Desert Organisms(Plants)

Cactus spines are actually leaves

Cacti are SUCCULENTS, meaning they store water

Aloe vera is also a succulent

Desert Plants cont. Most plants have

shallow roots but some have long roots, like the mesquite tree which has roots 20m deep.

Desert Animals Insects, birds,

reptiles, and mammals

Insects and reptiles have an outer coating to reduce water loss

Most animals are NOCTURNAL meaning they are active at night. Why?

Deserts cover over 30% of Earth’s surface Deserts of the northern belt are found near

the Tropic of Cancer (23ºN) Deserts of the southern belt are found near

the Tropic of Capricorn (23ºS)

Winds move from west to east As they move, moisture is drawn up The newly formed clouds then move up

over the mountains and drop their moisture

The air now is very dry (on the east side), resulting in the formation of a desert OR

A SEMIARID region (not as dry as a desert)

The drying of the eastern side is called the RAINSHADOW EFFECT

The transformation of semiarid land into desert is called DESERTIFICATION

How does this occur?

The Tundra is cold, windy, dry region Tundra is located in Northern Hemisphere in

Alaska, Canada, Greenland, Iceland, Scandinavia and Russia

Takes up 10% of Earth’s Surface Lack of biodiversity makes Tundra unstable

Tundra receives 25cm of precipitation per year

Temp rarely reaches above 10ºC Temperature is limiting factor of Tundra Tundra soil has an ACTIVE ZONE, which may

only be 8cm thick Below that, where the ground never thaws

is the PERMAFROST

Mosses and grasses cover the active zone in the summer

Water cannot drain in Tundra This causes the formation of bogs, marshes,

and small streams This gives mosquitoes and black flies

chances to breed, keeping the food chain intact

Tundra Plants Very small, grow

close to ground

Tundra Animals MIGRATION or

seasonal travel brings in animals

Birds, Arctic Fox, Caribou

Musk oxen, coastal polar bears, and wolverines

Finish Worksheets for Chapter 7