Plate Tectonics

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Plate Tectonics

• Aims
• To understand the four different types of plate
  boundaries and the natural hazards associated
  with them.

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• The Location of volcanoes and earthquakes around
  the world
• Volcanoes occur
• In narrow bands
• Most often at destructive plate margins
• Along constructive plate margins e.g. Mid
  Atlantic Ridge
• They do not occur at collision margins and
  conservative margins.
• There is a concentration of volcanoes around the
  Pacific Ring of Fire

Ext Suggest a reason why there are no active
volcanoes in Britain.
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• Earthquakes occur
• In long narrow bands
• In a dense ring around Pacific ocean
• Down the entire length of the Mid-Atlantic ocean
• Along all types of plate margin
• Close to volcanoes
• On land or underwater
• Earthquakes and volcanoes have a similar but not
  identical global distribution.

Ext What do you think continental drift is about
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Plate Tectonics
Millions of years ago it is believed that the
world was once one huge super continent named
Pangea Through the process of continental drift,
the world became what we know today.
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Plate Boundaries
The black indicates the position of the
continents today. Each of the coloured parts are
the plates.
Around the pacific plate (green) is the pacific
ring of fire many volcanoes and earthquakes
are located here.
The plates move at different speeds and in
different directions. This is because of the
convection currents that operate underneath the
earth.
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Plate movement
The diagram shows the different convection
currents at work within the earth. Convection
currents flow in different directions according
to where the plate is.
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Constructive plate boundariesConstructive plate
boundaries are caused when two plates move away
from each other (diverge). When they move apart
from each other a gap is created. The gap is
filled with hot, molten lava that solidifies when
it reaches the surface (meeting either the sea or
air). Land is therefore formed. Earthquakes and
volcanoes are associated with constructive plate
margins.
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Destructive Plate Margins

• At a destructive plate margin, the heavier
  oceanic crust slides under the lighter, less
  dense continental crust.
• This results in both volcanoes and earthquakes,
  due to land being lost (destroyed).

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Collision Plate Margins

• Collision plate margins occur where two
  continental crust plates meet. As they are the
  same density neither is able to slide under the
  other one. Therefore, fold mountains are created.
  Earthquakes are common at collision plate
  boundaries.

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Conservative Plate Margins

• Earthquakes are associated with conservative
  plate margins. They are caused by the friction as
  the plates rub next to each other.

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Copy and complete the table
Ext Why do only weak earthquakes occur at
constructive margins?
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GCSE questions (contd)

• 1. What is the Pacific Ring of Fire? (2)
• 2. Briefly explain how volcanoes are created at
  a) Constructive and b) destructive plate margins
  (6)
• 3. Name one volcano from North America, South
  America, Europe and Asia
• 4. What are plates? What causes them to move?
• 5. Give three differences between continental and
  oceanic crust Ext.
• Pages 210-211 will help you

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Answers
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Homework

• Explain what the following words mean plate,
  plate boundary/margin, mantle, oceanic crust,
  continental crust, collision zones, constructive
  margin, destructive margin, conservative margin,
  Pacific Ring of Fire, continental drift.
• Ext - Research a volcano or earthquake

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Useful website

• www.bbc.co.uk/gcsebitesize