Chapter 7
Desert and Tundra
DESERTS
 RECEIVE LITTLE RAIN – 10-25
cm per year
 SOIL IS RICH IN MINERALS –
but poor in organic material
(nutrients) because there is NO
LEACHING – rain that carries
minerals deeper into the soil
 SOIL is loose and dry and
blows away easily in the wind
 PAVEMENT – hard desert floor
is exposed (hard-baked sand
and rock)
DESERT TYPES
TWO TYPES IN NORTH AMERICA
Badlands National Park, South Dakota
 COOL DESERTS –to the east of
mountain ranges in the north
western U.S. Ex: Sierra
Nevada, Rocky Mountains
 HOT DESERTS – in the
southern U.S. (Ex: Arizona,
New Mexico, western Texas,
Mexico)
Anza-Borrego Desert State Park, Texas
DESERT CLIMATE
 Very Low Rainfall – 10-25 cm in
any single year
 Most deserts receive less than
10 cm
 Few short thunderstorms with
long dry periods
 Temperature Variation – great
variation due to lack of
moisture in the air Ex: freezing
cold at night and searing hot
during the day
DESERT PLANTS
 Must be able to Absorb and
Hold Water in thick spongy
tissues (Ex: Cacti or Aloe vera
which are succulents)
 Adapt to Prevent Water Loss
(spines on cactus are modified
leaves)
 Have broad shallow roots
(cacti) or very deep tap roots
(mesquite and Joshua tree)
DESERT ANIMALS
 Many types of animals: insects
reptiles, birds and mammals.
 Insects and reptiles have thick
outer shells (scorpion, tarantula)
or scales (gila monster) to
protect them from the harsh
climate and retain water
 Mammals either stay
underground during the day
(kangaroo rat) or have
adaptations like the long ears of
the fennec which help to release
heat from their bodies
DESERT FORMATION
 Deserts are on every continent
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except Antarctica
Desert belts form on either
side of the equator
Sun rays heat the air at the
equator causing rapid
evaporation followed by
repeated rainfall
The dry air that’s left after the
rain moves towards the poles
This causes deserts to form
DESERT FORMATION
RAINSHADOW EFFECT –
 In the U.S. winds move from the
west coast toward the east coast
 Moist air from the Pacific passes
over the Sierra Nevada
mountains - the cold air forces
the water out and leaves cool
dry air to continue towards the
east.
 The cool dry air takes any
moisture from the soil east of
the mountains and causes
deserts to form
DESERTIFICATION
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Regions near deserts that are not as
dry are called SEMIARID (partially
dry).
HUMAN ACIVITY such as
overgrazing, deforestation, bad
farming practices all cause
vegetation loss. Climate change and
drought also cause desertification.
Lack of vegetation causes soil
erosion, leaving hard packed dirt
and rocks exposed.
This changes weather patterns,
heats the air and land and starts
desert formation.
Spreading deserts are found in
Africa, China, Europe (Spain), South
America, the Caribbean and the U.S.
Results in between 6 and 12 million
square kilometers of soil loss.
TUNDRA
 COLD, WINDY DRY REGION
 LOCATED JUST BELOW THE
NORTH POLE
 ALASKA, CANADA,
GREENLAND, ICELAND,
NORWAY, SIBERIA, ASIA
 LARGEST BIOME IN AREA –
10% OF THE EARTH’S
SURFACE
 LIMITED BIODIVERSITY –
FRAGILE AND UNSTABLE
ECOSYSTEM
TUNDRA FACTS
 Less than 25 cm precipitation
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(mostly snow and ice) per year
Air temperature rarely rises
above 10oC (50o F) which is the
limiting factor for this biome
PERMAFROST – only the top
layer (~ 8 cm) of soil ever
defrosts - the rest stays frozen
Rainfall can’t soak into the
ground forms marshes and
bogs instead
Plants stay low to the ground
and do not recover quickly
TUNDRA PLANTS
 Short growing season (60
days)
 Mosses, lichens, low shrubs
and grasses – few trees
(willows and birch) are very
small
 Roots are shallow, because of
PERMAFROST
 Have to be able to survive long
cold winters with no light for 6
months
TUNDRA ANIMALS
 Many tundra animals migrate
(long-distance seasonal travel)
with the weather and the food
sources like migrating birds.
 Arctic hare, lemmings, ground
squirrel, caribou, musk oxen,
puffin, snow goose, arctic loon
 Few predators: Arctic fox,
polar bears, snowy owl,
wolverines, wolves,
CHAPTER 7 VOCABULARY
 LEACHING
 PREMAFROST
 PAVEMENT
 MIGRATION
 SUCCULENT
 CLIMATOGRAM
 NOCTURNAL
 RAINSHADOW EFFECT
 DESERTIFICATION