Plate Tectonics Became a theory in the 1960s Describes plate movements AND explains why they move Plate Tectonics Two types of crust Oceanic and Continental Plates are usually made of both ID: 655098
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Slide1
The Theory of Plate TectonicsSlide2
Plate Tectonics
Became a theory in the 1960’s
Describes plate movements AND explains why they moveSlide3
Plate Tectonics
Two types of crust: Oceanic and Continental
Plates are usually made of both
Plates: Chunks of lithosphere “floating” around on the
asthenosphereSlide4Slide5Slide6
Plate Boundaries
Three Types:
Divergent Boundaries: two plates moving away from each other
Plates move apart, molten rock from
asthenosphere
fills gap
Most found on ocean floor (mid-ocean ridges)
Rift valley: valley in the center of the mid-ocean ridgeSlide7
Divergent BoundarySlide8Slide9
Convergent Boundaries
Two plates colliding (Three types of collisions)
Ocean – Continental: ocean crust is denser, so it is
subducted
:
forced under the continental crust
Ocean trench forms
Subducting
crust melts, some rises through the continental crust to form volcanic mountainsSlide10Slide11
Convergent Boundaries
Continental-Continental: neither is
subducted
, but both are crumpled and uplifted, forming mountain rangesSlide12
Convergent Boundaries
Oceanic-Oceanic: one plate gets
subducted
, again forming an ocean trench
Melting crust rises to form a volcanic
island arcSlide13Slide14
Transform Fault Boundaries
Sliding and grinding past each other
Does not move smoothly – spurts of movement between periods of no motionSlide15Slide16
Causes of Plate Motion
Convection
Hot
asthenosphere
rises, cools, sinks
convection currents
Lithospheric
plates ride on top of these conveyer belts
Evidence: More heat near divergent plate boundaries than elsewhere along ocean floorSlide17Slide18
Causes of Plate Motion
Ridge Push
New rock at mid-ocean ridges is hot, less dense, rises higher
As it cools, it sinks away from the ridgeSlide19
Causes of Plate Motion
Slab Pull
When a plate
subducts
and sinks, it pulls the rest of the plate with it