Transcript for Unit 2 - OwlTeacher.com

Earth's Physical
Geography
Unit 2
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Our Planet, the Earth
• How does the Earth move
in space?
• Why do seasons change?
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The Earth and the Sun
Days and Nights
• The Earth travels
around the sun in
an oval-shaped
orbit.
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• It takes 365 1/4 days, or one
year, for the Earth to
complete one revolution
around the sun.
• As the Earth revolves, it is
also spinning on its axis.
• Each rotation (or complete
spin on the axis) takes
about 24 hours.
• It is daytime on the side
facing the sun and night on
the side away from the sun.
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The Earth and the Sun
Understanding Seasons
Why are the days longer in some parts of
the year?
• The Earth’s axis is at an angle.
• In about half of the Earth’s orbit, the tilt
causes a region to face toward the sun for
more hours than it faces away from the sun.
• Days are longer.
• In other regions that face away from the sun
for more hours, days are shorter.
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Why does the
temperature change
during the seasons?
• The warmth you feel at
any given time of year
depends on how
directly the sunlight falls
on you.
• Some regions receive a
great deal of direct
sunlight, while others
receive very little.
• This is also a result of
the
Earth’s
tilt
and
orbit.
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Looking at Latitudes
Line of Latitude
Equator
Gets Direct
Where is it? Sunshine on
0º
March 21
September 23
Tropic of Cancer
23 1/2º N
June 21
Tropic of Capricorn
23 1/2º S
December 21
Arctic Circle
66 1/2º N
Never
Antarctic Circle
66 1/2º S
Never
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Seasons
Spring and fall equinoxes: Days and
nights are almost equal everywhere
First day of winter, or winter
solstice, in Northern Hemisphere
Zones of Latitudes
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Looking at Latitudes:
Zones
Low Latitudes: The Tropics
• Area between the Tropic of Cancer and
the Tropic of Capricorn
• In this region, it is almost always hot.
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Middle Latitudes: The Temperate
Zones
• Area between the Tropic of Cancer and
the Arctic Circle
• AND the area between the Tropic of
Capricorn and the Antarctic Circle
• In this region, there are seasons, each
with a distinct pattern of daylight,
temperature, and weather.
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High Latitudes: The Polar Zones
• Area between the Arctic Circle and the
North Pole
• AND the area between the Antarctic
Circle and the South Pole
• In this region it is very cool to bitterly
cold.
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Land, Air, and Water
• What forces shape the land?
• What are the Earth’s major
landforms?
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Forces Inside the Earth
What is the Earth made of?
The Earth’s surface is made up of 75
percent water and 25 percent land.
Continents are unique, in part because of
their landforms, which include mountains,
hills, plateaus, and plains.
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Pangaea: The
Supercontinent
• Geographers
theorize that
millions of years
ago the Earth had
only one huge
landmass, which
they call Pangaea.
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• They believe that 200 million years ago,
some force made Pangaea split into several
pieces and begin to move apart, forming
separate continents.
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• The theory of
plate tectonics
explains why the
continents
separated.
• Continents are
part of plates
that shift over
time.
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The Movement of the Continents
When geographers first began to study world
maps, they realized that the continents look
like pieces of a jigsaw puzzle.
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Volcanoes, Earthquakes, and Shifting Plates
The world’s plates move in different
directions, causing a variety of effects:
Ridges: In some places, plates move apart,
and magma leaks through the cracks in
the crust. In the oceans, over time, the
cooling rock builds up to form lines of
underwater mountains called ridges.
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Volcanoes: In other places, the plates
push against one another, forcing
one plate under the other.
Tremendous pressure and heat
builds up causing molten rock to
explode on the surface.
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Earthquakes:
– Along plate boundaries, there are many weak
places in the Earth’s crust.
– When plates push against each other, the crust
cracks and splinters from pressure.
– These cracks are called faults.
– When the crust moves along faults, it releases
great amounts of energy in the form of
earthquakes.
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Forces on the Earth's Surface
Forces like volcanoes
slowly build up the
Earth. Other forces
slowly break it
down. These forces
may not be as
dramatic, but they
have important and
long-lasting effects.
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The Two Effects of Weathering:
1. Weathering breaks down rocks
into tiny pieces, wearing away the
Earth’s landforms. Many oncesteep mountains are now low and
rounded. Three things cause
weathering: wind, rain, and ice.
2. Weathering helps create soil. Tiny
pieces of rock combine with
decayed animal and plant material
to form soil.
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Erosion
• Once this breaking down has taken
place, small pieces of rock may be
carried to new places by erosion.
Erosion, together with weathering, help
slowly create new landforms.
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Air and Water: Two Ingredients for Life
Air
• The thick layer of gases that surrounds the
Earth is called the atmosphere.
• It provides life-giving oxygen for people
and animals and life-giving carbon dioxide
for plants.
• It also acts as a blanket, holding in enough
heat from the sun to make life possible.
• Winds distribute this heat around the
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globe.
Water
• Roughly 97 percent of Earth’s water is
found in the oceans.
• The rest is fresh water, or water without
salt. Most of that is frozen at the poles.
• Fresh water comes from lakes, rivers, and
rain. Much fresh water, called
groundwater, is stored in the soil.
• People need fresh water—the Earth has
enough, but some places have too much,
and others have too little.
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The World: Wind Patterns
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Climate and What Influences It
• What is climate?
• How do landforms and bodies of
water affect climate?
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Weather or Climate?
Weather
• What you check before you go
outside in the morning
• Day-to-day changes in the air
• Measured primarily by temperature
and precipitation
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Climate
• What you know from experience
happens from year to year
• The average weather over many
years
• The Earth has many climate regions.
• Climates are different in low, middle,
and high altitudes because latitude
affects temperature.
• Landforms, wind, and water also
affect climates.
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The Blowing Winds
• Wind and water help spread the
sun’s heat and keep the Earth from
overheating.
• Winds blow east–west and west–
east in part because of Earth’s
rotation.
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Winds blow north–south and south–
north because:
• Hot air rises and circulates toward
regions where the air is not as hot.
• Hot, moist air from the Equator rises
and moves toward the North Pole or
South Pole.
• Cold air sinks and moves toward
regions where the air is warmer.
• Cold, dry air from the poles moves
toward the Equator.
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Ocean Currents: Hot and Cold
The Earth’s rotation creates ocean currents. Warm water from the
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Equator
flows north or south to colder parts and cold water from the
poles flows toward the warm areas near the Equator.
The Ocean's Cooling and Warming Effects
Bodies of water affect climate in another
way too:
Why is a beach on a hot summer day cooler
by the ocean?
• Water takes longer to heat or cool than land.
• In the summer, a place near the ocean or a
lake will be cooler than an area farther away.
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• The water currents are colder than
the air, so the current absorbs heat,
making the temperature fall.
• In the winter, that area will be warmer.
• The water currents are warmer than
the air, so the current gives off its
warmth and the air temperature rises.
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Raging Storms
Wind and water can make climates milder,
but they also can create storms. Some storms
create great destruction.
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Hurricanes
•
•
•
Wind and rain storms that form in the
tropics in the Atlantic Ocean
The winds at the center travel over 73
miles per hour.
They produce huge waves called storm
surges, which flood over shorelines and
can destroy homes and towns.
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Typhoons
• Similar to hurricanes, they
take place in the Pacific
Ocean.
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Tornadoes
•
•
•
•
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Swirling funnels of wind
that can reach 200
miles per hour.
The powerful winds can
wreck almost anything
in a tornado’s path.
However, they only
average about one half
mile in diameter.
Therefore they affect a
more limited area than
hurricanes.
How Climate Affects Vegetation
• Where are the
Earth’s major
climate regions?
• What kinds of
vegetation grow
in each climate
region?
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Climate and Vegetation
• Plants have features, called adaptations, that
enable them to live in a particular climate.
• Over a very long time, small, accidental
changes in a few individual plants made them
better able to survive in a particular place.
• Therefore, geographers can predict the kinds of
plants they will find in a climate.
• Each climate has its unique vegetation, or
plants that grow there naturally.
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Geographers discuss five broad
types of climates:
1. Tropical
2. Dry
3. Moderate
4. Continental
5. Polar
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Tropical and Dry Climates
Tropical Climates
Dry Climates
Tropical Wet
Tropical Wet and Dry
Arid
Semiarid
Temperature
Hot
Hot
Moisture
Wet
Dry
Tropical rain forest: Because
there is so much light, heat,
and rain, thousands of kinds
of plants grow here. The
uppermost branches of tall
trees create a canopy, and
plants more adapted to
shade grow beneath.
Sparse: Because there is so
little rain, plants grow far
apart and have shallow
roots adapted to absorb
scarce water before it
evaporates. Some plants
flower only when it rains.
Types
Vegetation
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Moderate Climates
Moderate Climates
Types
Temperature
Moisture
Vegetation
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Mediterranean, Marine West Coast, Humid Subtropical
Seasonal, but almost never below freezing
Moderate rain
In General: A wide variety—forests of deciduous trees,
tall shrubs, low bushes, a variety of grasses
Humid Subtropical: Has the most heat and
precipitation and many types of vegetation
Marine West Coast: Mountainous and cooled by ocean
currents—supports more forests than grasses
Mediterranean: Rainy winters and hot, dry summers
lead to plants with leathery leaves, which hold in
moisture during the dry summers.
A Vertical Climate
• A mountain is an example of a vertical
climate, where the climate changes according
to the mountain’s height.
• A hike up a tall mountain in a moderate
climate would go something like this:
– Grasslands surround the base, and
temperatures are warm.
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• You soon enter
a region with
less
precipitation
than below—
there are short
grasses, as in a
continental
climate.
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• Next, you move through deciduous forests
where it is cooler and drier.
• Slowly the forests change to coniferous
forests.
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• Then, you find only scattered, short trees
and finally only low shrubs and short
grasses.
• Soon it is too cold and dry even for them
and you begin to see mosses and lichens
of a tundra.
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• At the mountaintop is an icecap
climate, with no vegetation.
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