The Restless Earth AQA Geography GCSE

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  • Created on: 04-05-14 18:54
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The Restless Earth
Tectonic Plates
The Earth's Surface is Separated into Tectonic Plates
1) At the centre of the Earth is a ball of solid iron and nickel called the core
2) Around the core is the mantle, which is semi-molten rock that moves very slowly.
3) The outer layer of the earth is the crust. It's very thin (about 20km).
4) The crust is divided into lots of slabs called tectonic plates (they float on the mantle). Plates
are made of two types of crust- continental and oceanic:
Continental crust is thicker and less dense.
Oceanic crust is thinner and denser.
5) The plates are moving because the rock in the mantle below them is moving.
6) The places where plates meet are called boundaries or plate margins.
There are Three Types of Plate Margin
Destructive Margins
Destructive margins are where two plates are moving
towards each other, e.g. along the east coast of Japan.
1) Where an oceanic plate meets a continental
plate, the denser oceanic plate is forced down
into the mantle and destroyed. This often
creates volcanoes and ocean trenches (very deep sections of the ocean floor where
the oceanic plate goes down).
2) Where two continental plates meet, the plates smash together, but no crust is
Constructive Margins
Constructive margins are where two plates are moving
away from each other, e.g. at the mid- Atlantic ridge.
Magma (Molten rock) rises from the mantle to fill the
gap and cools, creating new crust.
Conservative margin
Conservative margins are where two
plates are moving sideways past each
other, or are moving in the same direction but at different speeds, e.g. along the west coast of the
USA. Crust isn't created or destroyed.

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Fold Mountains
Fold Mountains are formed when Plates Collide at Destructive Margins
1) When tectonic plates collide the sedimentary rocks that have built up between them are
folded and forced upwards to form mountains.
2) This means Fold Mountains are formed at destructive plate margins and places where there
used to be destructive margins.
3) You get Fold Mountains when oceanic and continental plates collide.
4) You also get Fold Mountains where two continental plates collide.…read more

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Some volcanoes also form over parts of the mantle that are really hot (called hotspots).
There are Different types of Volcano
1) Composite volcanoes (e.g. Mount Fuji in Japan)
Made up of ash and lava that's erupted, cooled and hardened
into layers.
The lava is usually thick and flows slowly. It hardens quickly to
form a steep-sided volcano.
2) Shield volcanoes (e.g. Mauna Loa on the Hawaiian islands)
Made up of only lava
The lava is runny.…read more

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Flat (unlike normal volcanoes, which are mountains)
Cover a large area (much bigger than normal volcanoes)
Have a caldera (unlike normal volcanoes where there's just a crater at the top)
When a Supervolcano Erupts there will be Global Consequences
1) A supervolcanic eruption will throw out thousands of cubic kilometres of rock, ash and
lava (much more than normal volcanoes, which usually produce a couple of cubic kilometres).…read more

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Earthquakes can be measured using two different scales:
1) The Richter scale:
This measures the amount of energy released by an earthquake called the
Magnitude is measured using a seismometer- a machine with an arm that moves
with the vibrations of the earth.
The Richter scale doesn't have an upper limit and it's logarithmic ­ this means that
an earthquake with a magnitude of 5 is ten times more powerful than one with a
magnitude of 4.…read more


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