1. Environmental Science
Chapter 7
Sections 1, 2 & 3

2. Deserts 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

3. Deserts
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

4. United States Deserts 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

5. Deserts 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

6. Deserts 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?

7. Formation of Deserts 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)

8. Formation of Deserts 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

9. Formation of Deserts
The transformation of semiarid land into desert is called DESERTIFICATION
How does this occur?

10. Tundra 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

11. Tundra 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

12. Tundra 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

13. Tundra Organisms 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

14. Assignment for Tomorrow
Finish Worksheets for Chapter 7