Geography: The Restless Earth - Revision Guide

This is the Revision Guide I made to help me through The Restless Earth Section in AQA GCSE Geography

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  • Created by: Gabby2805
  • Created on: 02-07-14 21:24
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The Restless Earth
The Structure of the earth:
At the centre of the earth, there is a ball of solid iron
and nickel called the core. Around the core is the
mantle, which is semimolten rock that moves very
slowly. The outer layer of the Earth is the crust which
is very thin (approx. 20km). The crust is divided into lots of slabs called tectonic
plates they float on the mantle. Plates are made up of two types of crust: oceanic
and continental. Continental crust is thinner and less dense oceanic crust is
thicker and more dense. The plates are moving because the rock in the mantle
underneath them is moving. Convection currents within the mantle determine the
direction of plate movement. The places where plates meet are called
boundaries or plate margins.
4 Types of Plate Margins:
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Destructive Margins
A destructive margin is when
oceanic crust moves towards
continental crust, for example
the Nazca plate moving towards
the South American plate. As the
oceanic crust is heavier, it is
forced downwards. As it is
forced downwards, pressure
increases which can trigger extremely violent earthquakes. At the same time, the
heat produced by friction turns the descending crust back into liquid rock called
magma. This happens in the subduction zone (an ocean trench) zone. Hot
magma tries to rise to the surface.…read more

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Fold Mountains
Young fold mountains are formed along the
plate margins where great earth movements
take place.
There were long periods of quiet between Earth
movements during which sedimentary rocks
thousands of meters thick formed in huge
depressions called geosynclines. Rivers
carried sediments and deposited them into the
depressions. Over millions of years the sediments
were compressed into sedimentary rocks such as
sandstone and limestone. These sedimentary
rocks were then forced upwards into a series of
folds by the movement of tectonic plates.…read more

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Austria and Slovenia. The highest peak is Mont Blanc near the FrancoItalian
border at 4810 meters, but there are many other peaks above 3800 meters.
Human activity...
Farming & Forestry: Most farms are located on the sunnier and warmer
southfacing slopes. The traditional pattern of farming is dairy farming using a
system called transhumance, the seasonal movement of animals.…read more

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Hydroelectric power (HEP) and Industry: The steep slopes, high
precipitation and summer melting of the glaciers produce fastflowing rivers that
are ideal for generating HEP. The narrow valleys are easy to dam and there are
lakes in which to store water. Some of the cheap HEP is used by industries which
require a high input of electricity such as sawmills, electrochemicals and fertiliser
manufacture and aluminium smelting. Some of the electricity is also exported to
other regions to supply towns and cities.
Population...…read more

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Volcanoes are divided into two main types, depending upon the material thrown
out in an eruption and the form (height and shape) of the volcanic cone produced:
Type Shield Composite Cone
Plate margin Constructive Destructive
Formation As the plates move apart, When the plates collide, the
magma rises to fill the denser oceanic plate is
gap. This adds new rock pushed down into the mantle.
to the spreading plates.…read more

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Examples Hekla & Surtsey, Iceland Etna & Vesuvius, Italy
Mauna Loa & Kilauea, Krakatoa, Indonesia
Hawaii Mount St. Helens, USA
Nyriagongo, the Congo
(Africa)
Why people live near volcanoes...
It has been estimated that 500 million people now live in areas that are likely to be
affected by earthquakes and volcanic eruptions. People are even migrating there
with this knowledge and the populations of some of these places are increasing.
The main reasons...…read more

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Other reasons:
They may believe that they are safe to be near a volcano that has been dormant
for a long time
It is much cheaper to live in these areas and people may not be able to afford to
live anywhere else
They trust the scientific information and feel adequately prepared
They have always lived here and do not want to break family traditions
For many people it would seem that the advantages of living in a danger zone far
outweigh the risk of…read more

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Residents had been told to leave and visitors were not allowed
inside an 8km exclusion zone around the crater.
The expected, yet unpredictable, eruption happened at 8:32am on 18th May.
An earthquake measuring 5.1 on the Richter scale caused a landslide on the
northeast side of the mountain. This was the biggest landslide ever recorded and
the sideways blast of pulverised rock, glacier ice and ash wiped out all living
things up to 27km north of the crater.…read more

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