Transcript The Restless Earth

Unit 1 Physical Geography: The Restless Earth
Unit Lessons
•
Why is the earth’s crust so unstable?
•
What happens at plate margins?
•
How are our highest and deepest places created?
•
How do people use an area of fold mountains?
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How and where are volcanoes created?
•
How do volcanoes affect people?
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How can we monitor volcanoes and predict eruptions?
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What is a supervolcano?
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What are earthquakes and where do they occur?
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What were the causes, effects and responses to the Kobe earthquake?
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What were the causes, effects and responses to the Port au Prince
earthquake?
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Why is a tsunami hazardous?
Independent study
•
An account of the uses of fold mountains and adapting to life in Livigno,
The Alps
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A report of the eruption of Mount St Helens, USA on 18th May 1980
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A comparison of the earthquakes in Kobe, Japan and Port au Prince, Haiti
L
How are our highest and deepest places
created?
Learning Objectives
• To know how and why fold mountains form at collision
boundaries
• To know how and why ocean trenches form at destructive
subduction margins
Key terms: Geosyncline, collision boundary, destructive-subduction boundary
Acting out Margins
• Use your hands to act out
what happens at a
destructive subduction,
constructive and
conservative margins
• Talk each other through
the stages!
• Help? Use your diagrams
Starter
2 mins
Quick Draw…
• You have 10 seconds… to draw the 4 layers of
the earth
• You have 20 seconds… to give two differences
between oceanic and continental crust
• You have 30 seconds… to draw and label a
destructive subduction margin
Our Highest and Deepest Places
• The highest places on Earth are fold mountains.
• The deepest places on Earth are ocean trenches.
• Both fold mountains and ocean trenches result from
plates moving together.
Destructive subduction
•Where fold mountains and ocean
trenches are found together they are a
result of destructive-subduction
•Where fold mountains are found by
Destructive collision
themselves they are a result of
destructive collision
A map to locate the world’s young fold mountains and ocean trenches
Destructive collision
Destructive subduction
Direction of
plate movment
Fold mountains
Ocean trenches
Ocean trenches form at destructive subduction margins (oceanic plate sinks beneath continental plate
e.g. Pacific Plate and North American Plate)
Young fold mountains form at both destructive subduction margins and destructive collision margins
(where two continental plates collide e.g. African plate and Eurasian plate)
Fold mountains in more depth
• Formed in last 65 million
years, young fold mountains
are the highest areas of our
planet.
• Ranges include the
Himalayas, the Rockies, the
Andes and the Alps.
• Older fold mountains like the
Cumbrian mountains have
been worn down via erosion
• Found at destructive
(subduction) and destructive
(collision) plate margins
The Alps, Europe’s highest fold mountains.
Young fold mountains: How they form
1. Geosynclines are
huge depressions
found naturally on
the ocean floor
Ocean
Geosyncline
2. Rivers deposit
sediment in these
geosynclines
4. Plates are forced
together at
destructive margins
(can be subduction
or collision)
Rivers
3. Sediments are
compressed and
turned to
sedimentary rocks
like limestone
5. Sedimentary
layers are forced
upwards into fold
mountains
Ocean trenches in more depth
• Form the deepest parts of the Earth
• Occur at destructive (subduction)
margins
• As oceanic plate is subducted
beneath the continental plate
creates deep ocean trenches. The
deepest ocean trenches are created
by oceanic-oceanic subduction.
Ocean trench
• Mariana trench is deepest part of
the world’s ocean.
• Created by the subduction of the
Pacific plate beneath the
Mariana plate (oceanic-oceanic)
Challenger Deep: The deepest part of Mariana
Trench and the lowest part of the Earth
• Challenger Deep is the lowest
elevation on the Earth’s crust at
11,035 metres deep.
• You can fit Mount Everest in the
Mariana Trench and there would still
be over a mile of water left above it.
Exam Technique Explanation
Explanation is an important technique. It is done best using clear, ordered
sentences. Higher level explanation will include key terms and diagrams.
1.
Explain how fold mountains
are formed? (4 marks)
Fold mountains form when
two plates collide at
destructive margins.
Sediments are deposited on
the ocean floor in
geosynclines. Layers of
sedimentary rock are
created. As the two plates
collide the sedimentary rock
is forced upwards into fold
mountains (e.g. Alps,
Europe)
Sediments deposited
in geosyncline
Layers of sedimentary forced upwards by
plates colliding, forming fold mountains
Exam Technique Explanation
Explanation is an important technique. It is done best using clear, ordered
sentences. Higher level explanation will include key terms and diagrams.
2. Explain how ocean
trenches are formed? (4
marks)
At a destructive
subduction margin the
oceanic plate sinks
beneath the continental
plate. As it subducts, the
seabed forms a deep
trench.
Destructive subduction
Ocean trench