Lesson 5 - Oceanic-Continental Convergence Flashcards
What occurs when an oceanic and continental plate meet?
Denser oceanic plate forces under lighter continental plate (Subduction)
What happens as the plate sinks into the mantle?
Acts to pull the rest of the plate behind it (Slab Pull)
What does the downwarping of a subducted oceanic plate form? (+ example)
Ocean trench
Peru-Chile trench
Nazca plate subducted underneath S.American plate
What builds up as the oceanic plate descends?
Friction with overlying continental crust
Why does this occur?
Plates unable to move past each other smoothly
Occasionally lock together
Pressure builds up
What takes place when this pressure is released?
Earthquakes
What does compression + folding of the continental crust create?
Fold mountain chains
On leading edge of continental land masses
E.g Andes, South America
What is created alongside friction when the slab of ocean floor descends?
Extreme heat (Also due to asthenosphere temperatures)
What does this cause?
Partial melting of the crust
What is the name of the area in which the crust is destroyed?
The Benioff zone
At which depths does the plate;
start to melt
Get completely destroyed
Beyond 100km
By 700km
What does the melting of ocean floor basalts create?
Basaltic lava
How does this lava behave + why is this the case?
Rises through fissures in the rock
Lower density than the mantle
How does it do this?
Burning/Stoping it’s way through overlying rock
What happens when this lava reaches the surface?
Form volcanoes + erupt
