Download Plate Tectonics

Plate Tectonics
Aims:
To understand the four
different types of plate
boundaries and the natural
hazards associated with
them.
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.
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
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.
Plate Boundaries
The black
indicates the
position of the
continents today.
Each of the
coloured parts are
the ‘plates’.
The plates move at different speeds
and in different directions. This is
because of the convection currents
that operate underneath the earth.
Around the pacific
plate (green) is the
‘pacific ring of fire’ –
many volcanoes and
earthquakes are
located here.
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.
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.
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).
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.
Conservative Plate Margins
Earthquakes are associated with
conservative plate margins. They are
caused by the friction as the plates rub
next to each other.
Copy and complete the table
Plate Margin Example of Earthquake/
Plates
volcano?
Constructive
Destructive
Collision
Conservative
Ext: Why do only weak earthquakes occur at
constructive margins?
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
Answers
Plate Margin Example of Earthquake/
Plates
volcano?
Eurasian plate/North Volcanoes and weak
Constructive American
earthquakes
Destructive
South
American/Pacific
Violent volcanoes and
strong earthquakes
Collision
IndoAutralian/Eurasian
Strong earthquakes
Conservative
North
American/Pacific
Strong earthquakes
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
Useful website:
www.bbc.co.uk/gcsebitesize