The Theory of Plate Tectonics
Transcript of The Theory of Plate Tectonics
The Theory of Plate Tectonics
What is the theory of Plate Tectonics?
Earth’s lithosphere is broken up into tectonic plates that move
around on top of the asthenosphere
What makes the tectonic plates move?
Convection Currents in
the mantle move the
plates as the core
heats the slowly-
flowing asthenosphere
(the elastic/plastic-like
part of the mantle).
These plates interact at
plate boundaries
Some key vocabulary …
Plate Boundary
location where edges of Earth’s tectonic plates meet
Stress
how the tectonic plates move past each other
Fault
break in Earth’s crust where
rocks move past each other
Divergent Boundary
•2 Types
Oceanic-OceanicContinental-Continental
•How are the plates moving?
Plates are moving apart from each other and separating
How are the rocks pulled? (Stress)
Rocks get thin in the middle
as the plates pull apart
This stress is called
“Tension”
What happens when the rock snaps from the stress of tension? (Fault)
a Normal Fault
Rock drops down
as it breaks
“Real World” Examples of Divergent Boundaries
Rift Valleys
(i.e. the Red Sea)
Mid-Ocean Ridges(i.e. the Mid-Atlantic Ridge)
Convergent Boundary
•3 Types
Oceanic-OceanicContinental-Continental
Continental-Oceanic
•How are the plates moving?
Plates are moving towards each other
Continental-ContinentalConvergent Boundary
•How are the plates moving?
Plates are moving towards each other to collide and bucklewhich causes the crust to thicken and push upwards
Continental-OceanicConvergent Boundary
•How are the plates moving?
Plates are moving towards each other and the Oceanic plate, which is colder & denser, subducts andmoves under the continental plate
Oceanic-OceanicConvergent Boundary
•How are the plates moving?
Plates are moving towards each other and one plate subducts under the other into the interior of the Earth
How are the rocks pulled? (Stress)
Rocks move towards one
another and collide
This stress is called
“Compression”
What happens when the rock snaps from the stress of tension? (Fault)
a Reverse Fault
Rock is forced upward
as it is squeezed
“Real World” Examples of Convergent Boundaries
Mountains(i.e. the Himalayan Mts.)
Trenches(i.e. the Mariana Trench)
Volcanoes(i.e. Mount St. Helens)
Transform Boundary
•How are the plates moving?
Plates are sliding past each other horizontally
How are the rocks pulled? (Stress)
Rocks are pushed in two
opposite directions
(pushed sideways – no
rock is lost)
This stress is called
“Shearing”
What happens when the rock snaps from the stress of tension? (Fault)
a Strike-Slip Fault
Rocks on each side
slip past each other
as they break
“Real World” Examples of Transform Boundaries
Dead Sea BasinFaults(i.e. the San Andreas Fault in
California)