Transcript Continental Drift and Plate Tectonics

Continental Drift and Plate
Tectonics
How the Earth’s Crust Changes
• Contients_a_drift26m.wmv
Alfred Wegener’s Discovery
• What did Alfred
Wegener discover?
• Looking at a map, he
decided that the
continents seemed to
fit together and at one
time, they must have
been together. He
called his super
continent “Pangaea”
• Came up with the
theory of Continental
Drift.
EVIDENCE FOR CONTINENTAL
DRIFT
• What evidence was
there for continental
drift?
• The continents fit
together like a puzzle.
• Mesosaurus fossils
were found on N.
America, S. America,
and Africa
• Glossopteris pollen
was found on almost
every continent.
EVIDENCE FOR CONTINENTAL
DRIFT
• What evidence was
there for continental
drift?
• The mountains of
Europe and N.
America were formed
at the same time and
made of the same
material.
• Diamonds in South
America and Africa
are the same type
and the same age
PLATE TECTONICS
• What is plate
tectonics?
• How do the plates
move?
• Plate tectonics is
Alfred’s theory taken
a step further.
• All of the lithosphere
(crust) is divided into
plates that move.
• Convection in the
mantle
CONVECTION
• What is convection
• Convection is a
process of heat
transfer.
• Warm magma rises
from the bottom of the
mantle, and cooler
magma sinks in a
circular motion
• The crust must move
due to the motion.
PLATE BOUNDARIES
• What are plate
boundaries?
• Places where the
plates of the crust
meet.
• What types of plate
boundaries are there?
• Divergent
• Convergent
• Transform
DIVERGENT
• What is a divergent
plate boundary.
• It is where two plates
are moving apart to
create new crust.
• Divergent boundaries
are also known as
spreading centers or
rift valleys
• The mid Atlantic
Ridge is the largest.
• New crust is created.
CONVERGENT PLATE
BOUNDARIES
• What is a convergent
plate boundary?
• It is where two plates
are moving together.
• There are three types:
1. Ocean/Ocean;
denser one sinks into
subduction zone
2. Ocean/Continent;
ocean plate will sink
into subduction zone
SUBDUCTION ZONES
• What is a subduction
zone?
• A place where the
crust goes back down
into the mantle to
remelt
• These are also known
as trenches
• Volcanoes are made
on the upper plate of
the subduction zone.
CONVERGENT PLATE
BOUNDARIES
• What is a convergent
plate boundary?
• The third type of
convergent plate
boundary is continentcontinent collision.
• Two continents hit,
crash and make
mountains
Continent Collision
TRANSFORM PLATE BOUNDARY
• What is a transform
plate boundary
• Where two plates
move past each
other.
• The famous transform
plate boundary is the
San Andreas fault in
California.