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Plate Tectonics (Plate Tectonics Theory (continental drift (Pangaea - '…
Plate Tectonics
Plate Tectonics Theory
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plate boundaries - conservative, destructive, constructive & collision
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Convection Currents
core heats the lava in the lower mantle, causing it become less dense and rise , when it reaches the cooler lithosphere, it cools down, becomes more dense and falls, beginning a cyclical process
Sea Floor Spreading - Harry Hess 1962 - used carbon dating to date the rocks, the youngest rocks were found in the middle of the mid atlantic ridge, proving the the sea floor spreads and continental drift is moving the plates apart
continental drift
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Laurasia - north american plate, asian plate and european plate
Gondwanaland - India, south america, africa, australasia, antarctica
Biological evidence
mesosaurus fossils were found in south american and african sediments of the same age, the mesosaurus was a freshwater fish that could not fly or swim
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climatological evidence
coal seams of a similar age were found in Antarctica, USA and UK
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Palaeomagnetism
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as the lava solidifies, this record becomes permanent
as the polarity of the earth changes, approx every 40,000 years , resulting in a series of magnetic stripes, aligning alternately with the north and south poles
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Earth's structure
crust - 0-100 km thick, split into tectonic plates
oceanic crust - younger, more dense, thinner, 0-10km, sima (silicon and magnesium based)
continental crust - 0-75km, older, thicker, less dense, sial (silicon and aluminium based)
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mantle - as hot as 3000 degrees and is plastic in the upper layer, the lower layer is made up of MAGMA and 600km in depth
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inner core - 6000 degrees and is solid iron and nickel, high pressure freezing and spherical in shape
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Ridge Push and Slab Pull
ridge push - when magma rises through the gap in a constructive boundary, and gravity pulls it down the sides of the ride
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