Plate TectonicsPlate Tectonics

Aims:Aims:To understand the four To understand the four

different types of plate different types of plate boundaries and the natural boundaries and the natural hazards associated with hazards associated with them.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 TectonicsPlate 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 BoundariesPlate 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 movementPlate 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 boundariesConstructive plate boundariesConstructive plate boundaries are caused when two plates Constructive plate boundaries are caused when two plates move away from each other (diverge). When they move move away from each other (diverge). When they move apart from each other a ‘gap’ is created. The gap is filled apart from each other a ‘gap’ is created. The gap is filled with hot, molten lava that solidifies when it reaches the with hot, molten lava that solidifies when it reaches the surface (meeting either the sea or air). Land is therefore surface (meeting either the sea or air). Land is therefore formed. Earthquakes and volcanoes are associated with formed. Earthquakes and volcanoes are associated with constructive plate margins.constructive plate margins.

Destructive Plate MarginsDestructive Plate Margins

At a destructive plate margin, the heavier oceanic At a destructive plate margin, the heavier oceanic crust slides under the lighter, less dense crust slides under the lighter, less dense continental crust.continental crust.

This results in both volcanoes and earthquakes, due This results in both volcanoes and earthquakes, due to land being lost (destroyed).to land being lost (destroyed).

Collision Plate MarginsCollision Plate Margins

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

Conservative Plate MarginsConservative Plate Margins

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

Copy and complete the tableCopy and complete the table

Plate Margin Example ofPlates

Earthquake/volcano?

Constructive

Destructive

Collision

Conservative

Ext: Why do only weak earthquakes occur at constructive margins?

GCSE questions (contd)GCSE questions (contd)

1. What is the ‘Pacific Ring of Fire’? (2)1. What is the ‘Pacific Ring of Fire’? (2)2. Briefly explain how volcanoes are created 2. Briefly explain how volcanoes are created

at a) Constructive and b) destructive plate at a) Constructive and b) destructive plate margins (6)margins (6)

3. Name one volcano from: North America, 3. Name one volcano from: North America, South America, Europe and AsiaSouth America, Europe and Asia

4. What are plates? What causes them to 4. What are plates? What causes them to move?move?

5. 5. Give three differences between Give three differences between continental and oceanic crust Ext.continental and oceanic crust Ext.

Pages 210-211 will help youPages 210-211 will help you

AnswersAnswers

Plate Margin Example ofPlates

Earthquake/volcano?

Constructive Eurasian plate/NorthAmerican

Volcanoes and weakearthquakes

Destructive SouthAmerican/Pacific

Violent volcanoes andstrong earthquakes

Collision Indo-Autralian/Eurasian

Strong earthquakes

Conservative NorthAmerican/Pacific

Strong earthquakes

HomeworkHomework

Explain what the following words Explain what the following words mean:mean: plate, plate, plate boundary/marginplate boundary/margin, , mantle, mantle, oceanic crustoceanic crust, continental , continental crust, crust, collision zonescollision zones, constructive , constructive margin, margin, destructive margindestructive margin, , conservative margin, conservative margin, Pacific Ring of Pacific Ring of FireFire, continental drift., continental drift.

Ext - Research a volcano or Ext - Research a volcano or earthquake earthquake

Useful website:Useful website:

www.bbc.co.uk/gcsebitesizewww.bbc.co.uk/gcsebitesize