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Plate Tectonics and Associated
Hazards.…read more

Slide 2

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The Earth's structure
· Core:
­ Dense rocks.
­ Contains iron and nickel alloys.
­ Solid inner core and molten outer core.
­ Temp over 5000°C
­ Approx 6371km below surface.
· Mantle:
­ Made up of molten and semi-molten rocks. Lighter elements; oxygen, silicon.
­ Magnesium and iron
· Crust:
­ Varies in thickness ­ thicker under continents than sea.
­ Lightest.
­ Made up of silicon, oxygen, aluminium, potassium, sodium.…read more

Slide 3

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Plate Tectonics Theory Lithosphere ­
Crust and upper
part of mantle.
· 1912 ­ Alfred Wegener ­ Continental Drift
­ Coal is found in UK but needs warm, wet conditions to form.
­ Continents fit together.
­ Fossils in South America and South Africa.
­ Pangaea was the name of the original single continent. He said it then split
into two continents ­ one in the north and one in the south.
· 1940s to 1960s ­ Plate tectonic theory
­ Lithosphere divided into plates which are moved by convection currents
­ Three main driving forces ­ Gravity, earths rotation, mantle convection.
­ Sea floor spread occurring.
­ Plates move due to convection cells in the mantle
­ Margins are the areas between the tectonic plates. Margins of converging
plates are called destructive margins while margins of diverging plates are
called constructive margins. Margins where the plates slide against each other
are called conservative margins.…read more

Slide 4

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Convection currents
· The plates move due to convection currents in
the mantle. These are hot currents of molten
rock that slowly move within the mantle and
cause the plates above them to move, usually
by as little as one or two cm each year.…read more

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Slide 6

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Destructive (convergent) plate
· Cause violent volcanoes and earthquakes.
· An oceanic plate and continental plate move towards each
· The denser (oceanic) plate dives under the continental one,
creating a deep ocean trench
· As the oceanic plate goes deeper into mantle it melts in the
subduction zone, due to friction and the increased
· The lighter molten rock will rise to the surface and create
· The continental crust is crumpled by the collision of the
plates which creates fold mountains.
· E.g. the Nazca plate dives under the South American plate.…read more

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