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The Restless Earth
Unit 1 Physical Geography: The Restless Earth
Unit Lessons
•
Why is the earth’s crust so unstable?
•
What happens at plate margins?
•
How are our highest and deepest places created?
•
How do people use an area of fold mountains?
•
How and where are volcanoes created?
•
How do volcanoes affect people?
•
How can we monitor volcanoes and predict eruptions?
•
What is a supervolcano?
•
What are earthquakes and where do they occur?
•
What were the causes, effects and responses to the Kobe earthquake?
•
What were the causes, effects and responses to the Port au Prince
earthquake?
•
Why is a tsunami hazardous?
Independent study
•
An account of the uses of fold mountains and adapting to life in Livigno,
The Alps
•
A report of the eruption of Mount St Helens, USA on 18th May 1980
•
A comparison of the earthquakes in Kobe, Japan and Port au Prince, Haiti
L
Why is the earth’s crust so unstable?
Learning Objectives
• To know the structure of the Earth
• To understand the crust is unstable, especially at plate margins
• To contrast oceanic and continental crust
• To describe the distribution of plate margins and tectonic activity
Key terms: Crust, plate, plate margin, mantle, oceanic crust, continental crust,
convection currents, destructive-subduction boundary, destructive-collision boundary,
constructive boundary, conservative boundary
The structure of the Earth
•
•
•
Convection
currents operate
in the mantle.
These determine
which way the
plates move.
•
Inner core - the centre and
hottest part of the Earth. Its solid
and made up of iron and nickel.
Temperatures up to 5500°C. Its
immense heat energy acts like
the engine room of the Earth.
Outer core - surrounds the inner
core. A liquid layer, also made up
of iron and nickel. Still extremely
hot, temperatures similar to inner
core.
Mantle - widest section of the
Earth. Diameter of approximately
2900km. Made up of semi-molten
rock called magma. In the upper
parts of the mantle the rock is
hard, but lower down the rock is
soft and beginning to melt.
Crust - outer layer of the earth. A
thin layer between 0-60km thick.
The crust is split into solid
tectonic plates, upon which we
live.
Contrasts between oceanic and
continental crust
Oceanic crust
• Newer, most
less than 200
million years
old
• Denser
• Can be
subducted
(sink)
• Can be
renewed and
destroyed
Continental crust
• Older, most
over 1500
million years
old
• Less dense
• Cannot be
subducted
(sink)
• Cannot be
renewed and
destroyed
Direction of plate
movement
North
American
The Plates
Eurasian
Pacific
African Plate
Nazca
South
American
Indo Australian
Plate
Antarctic
Remember the plates move (shown by the arrows). They move at the
TASK
map.
rateLabel
your your
fingerplates
nails grow.
Exam Technique Describing Distributions
Figure 1 below is a map of the earth’s tectonic plates and the places where
earthquakes occur worldwide. Describe how the distribution of earthquakes is linked
to the earth’s tectonic plates (3 marks)
Highest frequency of
earthquakes around
the Pacific Plate.
Earthquakes occur
most where plates are
moving towards or
sliding past another
Less earthquakes at
this between the
North America Plate
and the Eurasian
Less earthquakes
when the plates are
moving apart
Describing distributions is very important in Geography. You need to be able to use
this skill in all your GCSE units. When describing a distribution use the acronym
H.L.GT.A (highest, lowest areas, general trend, anomalies).
Plate margins – types, direction & examples
TASK Study map C on page 9. Fill in the table below.
Plate Margin
Direction of plate
Movement
Example of plate margin
Destructive subduction
Oceanic plate moves into and
subducts beneath continental
plate
Juan de Fuca Plate (oceanic)
subducts beneath North American
Plate (continental)
Destructive –
collision
Two continental plates collide,
both forced upwards (forming
fold mountains)
Indo-Australian Plate (continental)
collides with the Eurasian Plate
(forms Himalayas)
Constructive
Two plates move away from
each other (new land created
by rising magma)
North American Plate and the
Eurasian Plate (forms Mid Atlantic
Ridge)
Conservative
Two plates slide past one
another (neither is destroyed)
North American Plate slides past
the Pacific Plate (forms San
Andreas Fault)
Click to reveal the answers…
Questions
Use pages 8 and 9 to help you with these questions
1. Draw simple labelled diagram contrasting oceanic
and continental crust. Be sure to give three
differences between oceanic and continental crust.
(4 marks)
2. What are convection currents? How do they drive
the movement of plates above? (3 marks)
3. Describe how the distribution of earthquakes is
linked to the earth’s tectonic plates (3 marks)
4. At which plate margins do earthquakes occur at
most frequently? (2 marks)