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Plates on the Move
Three kinds of boundaries between plates “Divergent” – pulling part “Convergent – pushed together “Transform fault” – slide past each other
Divergent Boundaries
Plates pull apart & leave a gap Magma fills gap,
cools and hardens Examples:
Mid – Atlantic Ridge (beneath ocean)
Rift between North American plate and the Eurasian plate in Thingvellir Iceland
Convergent Boundaries
Plates ram into each other
Subduction process One plate cycles
under other Recycles earth’s
crust
Oceanic plate converging with Continental Plate Result: Oceanic
plate is “subducted” under the continental plate
Example: Juan de Fuca plate pushing under NA plate
Oceanic plate converging with another Oceanic plate Result: form a
“trench” where one oceanic plate slips under another
Example: Mariana trench Convergence
between Pacific plate and Phillipine plate
Continental Plate converging with Continental Plate When two
continental plates meet do not subduct
Instead crust buckles upwards forming Mountains (peak) Plateaus (flat)
Eg. Tibetan Plateau
Transform Fault Boundary
Two plates slide by each other
Most under ocean San Andreas Fault
Few land based TF Pacific Plate sliding
past North American plate
Complete the missing informationPlace on Earth
Type of Boundary
Description of Plate Movement
Thingvellir Rift NA plate pulling away from the Eurasian plate
Juan de Fuca Plate
(oceanic plate)
Convergent Boundary
(Oceanic + Continental)
Tibetan Plateau Indian plate pushing up Eurasian plate
San Andreas Fault Transform Fault Boundary
Answers
Place on Earth
Type of Boundary
Description of Plate Movement
Thingvellir Rift Divergent Boundary NA plate pulling away from the Eurasian plate
Juan de Fuca Plate
(oceanic plate)
Convergent Boundary
(Oceanic + Continental)
Oceanic plate subducting beneath NA Plate
Tibetan Plateau Convergent Boundary
(Continental + Continental)
Indian plate pushing up Eurasian plate
San Andreas Fault Transform Fault Boundary Pacific Plate sliding past NA Plate
At a Divergent boundary the plates are moving apart. The plates move apart due to convection currents inside the Earth.
As the plates move apart (very slowly), magma rises from the
mantle. The magma erupts to the surface of the earth. This is also accompanied by earthquakes.
When the magma reaches the surface, it cools and solidifies to form a new crust made up of igneous rock. This process is repeated many times, over a long period of time.
Eventually the new rock builds up to form a volcano. Divergent Boundaries tend to be found under the sea, e.g. the Mid-Atlantic Ridge. Here, chains of underwater volcanoes have formed along the plate boundary. One of these volcanoes may become so large that it erupts out of the sea to form a volcanic island, e.g. Surtsey and the Westman Islands near Iceland.
At a convergent boundary the plates are moving towards each other. This usually involves a continental plate and an oceanic plate.
The oceanic plate is denser than the continental plate so, as they move together, the oceanic plate is forced underneath the continental plate. The point at which this happens is called the subduction zone. As the oceanic plate is forced below the continental plate it melts to form magma and earthquakes are triggered. The magma collects to form a magma chamber. This magma then rises up through cracks in the continental crust. As pressure builds up, a volcanic eruption may occur.
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