Unit 1 Physical Geography: The Restless EarthUnit 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? • How and where are volcanoes created? • How do volcanoes affect people? • How can we monitor volcanoes and predict eruptions? • What is a supervolcano? • What are earthquakes and where do they occur? • What were the causes, effects and responses to the Kobe earthquake? • What were the causes, effects and responses to the Port au Prince

earthquake? • Why is a tsunami hazardous? Independent study• An account of the uses of fold mountains and adapting to life in Livigno,

The Alps• A report of the eruption of Mount St Helens, USA on 18th May 1980• A comparison of the earthquakes in Kobe, Japan and Port au Prince, Haiti

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

L

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 2 mins

Starter

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 themselves they are a result of destructive collision

Destructive collision

A map to locate the world’s young fold mountains and 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)

Direction of plate movmentFold mountains

Ocean trenches

Destructive subduction

Destructive collision

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

2. Rivers deposit sediment in these geosynclines

1. Geosynclines are huge depressions found naturally on the ocean floorGeosyncline

Ocean

3. Sediments are compressed and turned to sedimentary rocks like limestone

Rivers

4. Plates are forced together at destructive margins (can be subduction or collision)

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

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)

Explanation is an important technique. It is done best using clear, ordered sentences. Higher level explanation will include key terms and diagrams.

Sediments deposited in geosyncline

Layers of sedimentary forced upwards by plates colliding, forming fold mountains

Exam Technique Explanation

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.

Explanation is an important technique. It is done best using clear, ordered sentences. Higher level explanation will include key terms and diagrams.

Destructive subduction

Ocean trench