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Plate tectonics - Coggle Diagram
Plate tectonics
The big breakup
Plate tectonics is the process that split up the supercontinent into continental plates. Driven by convection currents in Earths mantle which causes hotter materials to rise and cooler materials to sink
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Over last 200 million years Pangea (super continent) spit into Gondwana and Laurasia.
Break-up with Gondwana started with rift valley that developed between Africa, South America, Antarctica and Australia.
Plate movement occurs at different speeds ranging from 1cm per year to 20cm per year.
Currently there are 7 major plates and a few smaller plates.
The process that caused plate tectonics
The lithosphere
Layer of rock that formed the most outer layer of the Earths crust, strong/rigid and brittle. (This is where tectonic continental plates are located) These plates extend into the ocean and meet other plates at mid-ocean ridges or at ocean trenches and fault zones.
Rift zones are long cracks in Earths crust between the tectonic plates. Rift formation = fundamental process of plate tectonics, which can split continents in half over time.
Pieces of Lithosphere float on asthenosphere.
(This is where tectonic continental plates are located)
The asthenosphere
Beneath Lithosphere, for approximately 200km, rock zone, Zone is hotter, very near to melting point and almost liquid, hence less brittle, more pliable, plastic-like more easily bent
How the asthenosphere moves tectonic plates
Extremely hot Earths mantle below Asthenosphere heat rock by conduction, heated rock expands becomes less dense than surrounding rock, warmer less dense rock moves upwards into relatively cooler rock, cooler rock less dense thus less buoyant, denser and relatively cooler rock sink to complete convection cycle , tends to occur at continental margins/ which are also being forced downwards by subduction.
Convergent and divergent zones
Slow-moving convection current in Asthenosphere provides enormous force that moves continental plates.
Three major plate Movements:
-Convergent movement
-Divergent movement
-Transform movement
Convergent plate movement
Continental plates that move towards each other, meet at a convergent zone.
Process of subduction occurs at convergent plate boundaries, where sinking plate moves under upper one as edge of the the plate sinks into asthenosphere and into mantle.
Divergent plate movement
Continental plates move away from each other.
Divergent zone is where boundaries of 2 plates split apart.
Transform plate movement
Transform plate boundaries located where 2 plate sides pass one another. Most transform faults found in ocean basins and connect in mid-ocean ridges.
Small number of faults connect within mid-ocean ridges and subduction zones.
Seafloor spreading
Mid- Atlantic ridge and Atlantic ocean basin example of seafloor spreading. Ridge characterised by volcanic activity, with melted materials being extruded, at approximately middle of ocean basin. Molten rock brought up to seafloor from asthenosphere, through mid-ocean ridge system and cooled by ocean waters. Rock laid down at Mid-Atlantic ridge and over time moves away from ridge, towards land masses East and West.
We know this because of:
-Rock samples taken further from ridge= older than rock samples taken closer to ridge.
-Younger rock closer to ridge has less sediment accumulated on it and older rock closer to continent, which has thicker layer, has had more time for the accumulation of sediment.
-Quality of rock material are similar, same distance on either the West or East side of ridge.