Download They believe that 200 million years ago, some force made Pangaea

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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Divergent
 Occurs when two plates move away from each other
 What kind of landforms do you think this creates?
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Valleys
•Forces are strong
enough to cause the
plate to split apart
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Convergent
 When two plates move towards each other, they would
collide.
 What does this cause?
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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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Transform
 Movement when two plates slide laterally past each
other.
 When there is sufficient buildup of pressure, rocks in
the plates break and get jerked apart.
 What landforms does this cause?
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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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Brain Break!
Stand up and practice your hand
movements for Divergent,
Convergent, and Transform with
your elbow partner.
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Land, Air, and Water
What forces shape the land?
What are the Earth’s major
landforms?
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The Two Effects of Weathering:
1. Weathering breaks down rocks into
tiny pieces, wearing away the
Earth’s landforms. Many once-steep
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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Plate Tectonics
• This theory says that the Earth’s crust is
made of huge, slowly moving slabs of
rocks called plates.
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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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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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Ocean Currents: Hot and Cold
The Earth’s rotation creates ocean currents. Warm water from the
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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Physical Features
 Erosion


 Plate Tectonics


 Ocean Currents


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On a separate sheet of
paper, list at least two
physical features that
can be created by
those environmental
processes.