What causes earthquakes and volcanoes?

To understand the theory of plate tectonics

To be able to explain how convection currents work

Use page 184 to label your cross section with information and distances.

Pictures to help you...

piece

What questions can we ask about our world map?

In 1912, a German scientist called Alfred Wegener proposed that South America and Africa were once joined together and had subsequently moved apart. 

He believed that all the continents were once joined together as one big land mass called Pangaea and this was intact until about 200 million years ago.

The idea that continents are slowly shifting their positions is called continental drift.

What is continental drift?

http://www.youtube.com/watch?v=uGcDed4xVD4

Study of fossilsSimilar fossils are found on different continents. This is evidence that these regions were once very close or joined together.

Shapes of continents Some continents fit together like a jigsaw. Africa

SouthAmerica

Pattern of rocksSimilar pattern of rock layers on different continents is evidence that the rocks were once close together or joined.

Evidence for continental drift

African

Indo-Australian Plate

North American

South American

Eurasian

Pacific

Nazca

Antarctic

Pacific

Plate names – the study of these plates is referred to as plate tectonics

Can you name plates A and B?

A

BAfrican Plate

Indo-Australian Plate

Plate names

Some plates are continental (like the North American Plate)

Some are oceanic (like the Pacific Plate)

It is at the MARGINS/ BOUNDARIES of

these plates where the action usually

happens

Tasks: pg 186

• Draw onto your map the plate boundaries.• Put arrows onto your map to show the

direction that the plates are moving in.

So why do the plates move?

Using only pencils, try to move the book across two tables. Now answer this

question! Use page 187 to help you and include a diagram.

http://www.youtube.com/watch?v=ryrXAGY1dmE

Want proof of convection currents?

• http://www.youtube.com/watch?v=ncut0iTnOgI

You can actually see

them working!

Why are some volcanoes more violent than others?

Structure of volcanoes

Types of volcano

Hazards associated with them

True or false?• One in 10 people in the world live within 'danger range' of

an active volcano. • Magma is dangerous on the surface of the earth.• There are around 1510 'active' volcanoes in the world. • 1510 volcanoes have erupted in the last 10,000 years,

which means they are active in the world of volcanoes. • There are thought to be many more volcanoes on the sea

bed. • Russia has the worlds tallest volcano at 3050m• The biggest volcano in the world is Mauna Loa in Hawaii.

Its whole volume is about 80,000 cubic kilometres. • Sometimes lightning is seen in volcanic clouds. It's not

clear why this happens but it could be to do with lots of hot particles bashing into each other, causing static charges.

T

T

TT

T

T

F

FLava

Cornflour Experiment

• This will explain why some volcanoes are tall and steep and others are wide and flat.

Destructive (Subduction Zone) volcanoes

• http://www.absorblearning.com/media/item.action?quick=12s

• http://www.absorblearning.com/media/item.action?quick=12y

At ……………. boundaries, when oceanic crust pushes down underneath …………….. crust it is known as a subduction …………. Friction causes the oceanic crust to……….. The newly formed hot …………… rises up and erupts violently. The volcanoes formed here are called …………..volcanoes, meaning they are tall and …………. sided. An example of this type of volcano is ………………………. in the USA.

destructive

continental

zone

melt composite

steep Mount St Helens

magma

Constructive Margin Volcanoes

• http://www.science-resources.co.uk/KS3/Chemistry/Earth_Structure/volcanoes.html

• Using page 198 and 188, make your own notes to explain how shield volcanoes form at these margins.

• KEY TERMS TO USE: shield, less viscous, not explosive, less gas trapped, wide and gentle, moving apart, plates.

Quick Revision Test

• You have 10 minutes to complete this test on the sheet on your own.

• I will start the time when the majority of people are in the lesson and ready to go.

• I will put your marks on the blog.

Hotspot Volcanoes

• http://education.sdsc.edu/optiputer/flash/hotSpots.htm

• Draw the diagram and use the book to explain how these are formed.

Name the HazardSwissEduc: Stromboli Online - Etna 1999

SwissEduc: Stromboli Online – Montserrat

Lahars

Lava

• Lava is magma which has escaped to the surface

Pyroclastic Flow/ Nuée ardentes

These are fast moving destructive clouds of hot gas, and ash. They can travel up to 320km/h km per hour. Mt Pelee produced a pyroclastic flow in 1902 which killed 29 000 people.

Lahars A mixture of water and rock flowing down the volcano slope. A lahar looks like a mass of wet concrete that can carry rock debris more than 10 m in diameter and move up to 95km/h.

Tephra• Tephra is a general term for fragments of

volcanic rock and lava that are blasted into the air by explosions.It can travel thousands of kilometers downwind from a volcano.

Summary sheet

• Complete the summary sheet to show how volcanoes can differ from each other.

Why are some volcanoes more violent than others?

Structure of volcanoes

Types of volcano

Hazards associated with them