Transcript Tectonic Plate Boundaries

Plate Tectonics
III. The Theory of Plate Tectonics.
Plate Tectonics: Explains how large pieces of the
Earth’s outermost layer, called tectonic plates,
move and change shape.
A.
Tectonic Plate Boundaries: A place where
tectonic plates touch
1. Convergent boundary
2. Divergent boundary
3. Transform (Strike-slip) boundary
NOAA Plate Tectonics Video
Convergent Boundary
Convergent boundary : formed by the collision of
two lithospheric plates.
3 types:
a) Continental-continental collision:
-Two plates with continental crust
collide buckle and thicken to form
mountain ranges.
Convergent Boundary
b) Continental-Oceanic:
-continental and oceanic plates collide.
-Denser oceanic crust sinks into
asthenosphere where it is recycled.
Subduction Zone
c) Oceanic-Oceanic Collisions:
-Two oceanic plates collide. One
of the plates is subducted, or
sinks under the other.
Subduction Zone
Plate Tectonics: Subduction
Alaska’s Volcanic Arc
Subduction Zones
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-Subduction zone is an area where a plate
moves under another plate.
The Crust is recycled and causes volcanic
activity.
Subduction zones are normally located at deep
ocean trenches.
2. Divergent boundary: the boundary between two
tectonic plates that are moving away from each other.
Ex. Mid-ocean ridges.
3. Transform boundary: boundary between tectonic
plates that are sliding past each other horizontally.
-Ex. San Andreas Fault
Drilling for Core Samples
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Describe how the plates
are moving relative to
one another.
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What type of plate
boundary is this? Check
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What does the sea floor
topography look like in
this area?
B. Possible Causes of Tectonic Plate Motion
Convection: Hot rock from deep within the
Earth rises, but cooler rock near the surface
sinks.
-Causes lithosphere to move away from midocean ridge.