1. What causes earthquakes and
volcanoes?
To understand the theory of plate
tectonics
To be able to explain how convection
currents work
2. Use page 184 to label your cross section with information
and distances.
Pictures to help you...
piece
3.
4. 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=uGcDed
4xVD4
5. Study of fossils
Similar 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
South
America
Pattern of rocks
Similar pattern of rock layers on different continents is evidence that the rocks
were once close together or joined.
Evidence for continental drift
7. Can you name plates A and B?
A
B
African Plate
Indo-Australian Plate
Plate names
8. 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
9. 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.
10. 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/w
atch?v=ryrXAGY1dmE
13. • 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
Lava
14. • This will explain why some volcanoes are
tall and steep and others are wide and flat.
15. • 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
18. 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.
23. 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.
24. 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.
25. 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.
26. • Complete the summary sheet to show how
volcanoes can differ from each other.
