The Restless Earth
Plate Tectonics
Map of Plate Boundaries
Plate tectonics is the theory that Earth's outer shell is divided into several plates that glide over the mantle.
Constructive Plate Margin
How is it formed?
Convection currents cause the plates to move apart
As the plates move apart the magma wells up from the mantle to form new basaltic oceanic crust (new plate area is formed).
The Earth’s surface area increases due to the formation of new oceanic crust – sea floor spreading
Destructive Plate Margin
How is it formed?
The thicker, denser oceanic plate slides beneath the continental plate (subduction)
The oceanic plate melts as it reaches the hot mantle
Folding of the continental plate forms mountains
As the plates slide past each other, friction stores energy in rocks – energy is released in earthquakes
Collision Plate Margin
Conservative Plate Margin
How is it formed?
As the plates slide horizontally past each other pressure builds up in the rocks either side of the fault.
Fault surface often rough – friction creates large strains along the faults.
An earthquake happens when the built up pressure and energy are released in a sudden, jerky movement.
Click on the link to open a summary of the different plate boundaries
Fold Mountains & Ocean Trenches
Our Case Studies:
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Bam, Iran 26th December 2003
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Tohoku, Japan 11th March 2011
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Japan Tsunami 11th March 2011
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Mount St Helens, USA 18th May 1980
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Sourfriere Hills, Montserrat 25th June 1997
Useful Websites:
Living on Fold Mountains
Bam Earthquake
Mt St Helens Eruption
Japan Tsunami in Numbers
Exam Questions:
http://www.bbc.co.uk/bitesize/ks3/geography/physical_processes/plate_tectonics/revision/3/
http://www.s-cool.co.uk/gcse/geography/tectonics/revise-it/plate-boundaries
2012
1 (c) Describe how earthquakes are measured using the Mercalli Scale.
1 (d) Describe how the effects of an earthquake in a richer area of the world are different from the effects of an earthquake in a poorer area o the world.
2011
1 (c) (i) Describe the size and shape of a supervolcano.
1 (c) (ii) Describe the likely worldwide effects of a supervolcano eruption.
2010
1 (c) (i) Explain why a tsunami is a secondary effect of plate movement
1 (c) (ii) Use a case study of a tsunami to describe its effects on coastal areas.
