Transcript The Theory of Plate Tectonics

Ch.4, Sec.3 - The Theory of Plate Tectonics
 plate tectonics: the theory that explains how large pieces of
the Earth’s outermost layer, called tectonic plates, move and
change shapes.
- a boundary is where the plates touch & there are 3 types:
convergent, divergent, and transform.
 convergent boundary:
formed by the collision
of two lithospheric
plates.
Plate
Plate
- there are three types of
convergent boundaries:
continental-continental,
continental-oceanic, &
oceanic-oceanic.
Ch.4, Sec.3 – The Theory of Plate Tectonics
 divergent boundary: the boundary between two tectonic
plates that are moving away from each other.
Plate
Plate
- mid-ocean ridges are the most common type of divergent
boundary.
Ch.4, Sec.3 – The Theory of Plate Tectonics
Ch.4, Sec.3 - The Theory of Plate Tectonics
 transform boundary: the boundary between tectonic plates
Plate Plate
that are sliding past each other horizontally.
- an excellent example of a transform boundary is the San
Andreas Fault in California.
Ch.4, Sec.3 - The Theory of Plate Tectonics
- plate motion is caused by the different densities in the
asthenosphere.
- thermal energy from the interior of the Earth rises to the
asthenosphere & heats rocks (they expand, become less
dense, and rise to the surface).
- three possible causes for tectonic plate motion are: ridge
push, convection, and slab pull. (pg.110)
- ridge push occurs when
oceanic lithosphere slides
downhill under the force of
gravity.
Ch.4, Sec.3 - The Theory of Plate Tectonics
- slab pull occurs when
oceanic lithosphere sinks
and pulls the rest of the
tectonic plate with it.
- convection occurs
when hot rock rises &
cool rock sinks, causing
oceanic lithosphere to
move sideways & away
from mid-ocean ridges.
- we can measure the
movement (only a couple
centimeters) of the plates
every year with GPS
systems!
Ch.4, Sec.3 - The Theory of Plate Tectonics