1. Higher Plate Tectonics
Aims:
To understand the four different types of plate boundaries and the natural hazards associated with them.
ELL Dec 2002

2. 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.

3. 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

4. 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.

5. 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.

6. 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.

7. Constructive plate boundaries Constructive 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.

8. 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).

9. 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.

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

11. Copy and complete the table
Ext: Why do only weak earthquakes occur at constructive margins?

12. 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 will help you

13. Answers

14. 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

15. Useful website: