Week 3 Flashcards
Continental margin
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2 types of continental margins
- Passive
Active
Passive
Passive: no break, gradual transition from continental to oceanic lithosphere. The plate can be both oceanic and continental lithosphere (there is no boundary)
Active
Plate boundary break in lithosphere. (Earthquakes and volcanoes). Can happen anywhere but not on a margin
Divergent plate boundary setting
Continental: rift zones
Oceanic: mid ocean ridges
Rift zones
2 continental lithospheres diverging, pulls continents apart and makes seas( earthquakes and volcanoes ) the ground is dropping. Earthquakes weaken everything, it fills with magma and eventually turns to water
Mid ocean ridges
2 oceanic lithospheres spreading apart, density increases as you go away from the ridge because it gets more dense with age, it is hot in the middle and cools as it goes out making it more dense
How do we know we have a plate boundary
When we see a trench, and a series of volcanoes follows it u
Magma only forms from ____
Subduction zones
Convergent boundaries are also called ____
Subduction zones
Subduction zones happen because
Lithosphere is being subducted into the mantle the density of the lithospheric plate is more dense than the asthenospehere
What is more dense: oceanic or continental crust
Oceanic
Only oceanic lithosphere _____
Will subduct
How do convergent plate boundaries form volcanoes (oceanic cont)
Oceanic crust subducts ad creates magma that comes up and makes volcanic arcs
How do convergent plate boundaries form volcanoes (oceanic oceanic)
The older crust subducts and magma comes up
How do convergent plate boundaries form volcanoes (cont cont)
Can’t subduct. They crunch into each other, thickening the crust and creates mountains
Transform plate boundary
Plates move away and rub against each other, new oceanic crust is formed. The grinding together creates earthquakes
How do we know we have a plate boundary
Look down and there’s a trench and a series of volcanoes follows it
Why is rate of lithosphere production equal to destruction
Older, denser portions descend into the mantle at a rate equal to seafloor production
How do mountain belts form
Collision of 2 converging continental fragments
Evidence to prove plate techtonoc theory
Drilling
