Plate Tectonics and Associated Hazards plate movement and earth structure

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  • Created on: 11-09-12 00:21
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Plate Tectonics and Associated Hazards
Earth Structure:
Earth is split into 3 layers: The crust, the mantle and the core
.
Core: made of dense rocks containing iron and nickel alloys
Divided into solid inner core and a molten outer core
Over 5,000 degrees
Mantle: Molten and semimolten rocks containing lighter elements ­ silicon and oxygen
Crust: Light ­ containing silicon, oxygen, aluminium, potassium and sodium
Made of two types ­ continental and oceanic
Further Divisions:
Lithosphere: Crust and upper section of the mantle
Approximately 8090 km thick
Divided into 7 large plates and a number of smaller ones which are sub
divided into oceanic and continental depend on their make up
Asthenosphere: The semimolten material on which the plates float and move
Continental crust Oceanic crust
Thickness 3070 km 610 km
Age Over 1,500 million years Less than 200 million years
Density 2.6 (lighter) 3.0 (Heavier)
Composition Mainly granite silicon, aluminium Mainly basalt silicon, magnesium,
and oxygen (SIAL) oxygen (SIMA)

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Plate Movement:
Theory of Plate Tectonics: (Alfred Wegener 1912)
300 million years ago a single continent existed ­ called Pangaea
Later Split into two continents ­ Laurasia in North and Gondwanaland in the South
Today's continents were formed by further splitting of these two…read more

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Evidence that these areas were once joined
Geological Evidence:
continents seem to fit together well ­ Bulge of South America fitting into the indent
below west Africa
Evidence of glaciations of late Carboniferous period with deposits found in South
America, Antarctica and India ­ suggests they were formed together and then
moved
Striation rocks in Brazil and west Africa suggests they were formed together and
then moved
Rock sequences in Northern Scotland closely agree with those found in Eastern
Canada ­ suggest they were laid…read more

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Examination of the ocean crust on either side of the midAtlantic ridge suggested
seafloorspreading was occurring ­ shown by alternating polarity of the rock that form the
crust
Lava particles in lava erupted on the ocean floor are aligned with the Earth's magnetic
field.…read more

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