Transcript The Theory of Plate Tectonics

Science
Do Now: 12-8
EQ: What are plates and how do
they move?
LG: Describe the three types of tectonic plate
boundaries, the forces that move them, and how
movement is measured.
HW: 7-3 worksheet due Wed,
Test on Thursday study session at 8:15
** List 3 types of convergent boundaries use arrows to
show movement**
1. Take out color pencils/markers
2. Take out Plate Tectonic notes
Today
~ Complete PPT: Theory of Plate Tectonics
~ Convection Current Organizer
** List 3 types of convergent plate
boundaries use arrows to show
movement**
What is here?
1. Oceanic-Oceanic
2. Oceanic-Continental
What is here?
3. Continental-Continental
The Theory of Plate Tectonics
Think of a Broken EGG! 
Plate Boundary
Plate
Plate Tectonics
• The Earth’s lithosphere is divided into
plates that move on top of the
asthenosphere.
Lithosphere
Asthenosphere
When the water moves beneath
the raft, the raft moves with it.
When the asthenosphere moves,
the lithosphere moves with it…
Earth’s Major Plates
Here is a look at a different map!
Where are most plate boundaries located? What plate do we live on?
And another …
Types of Plate Boundaries
•
•
When two plates meet, they form a
boundary.
There are three types of boundaries
Convergent Boundaries
•
Two plates push together
Oceanic crust sinks,
Continental crust rises!!
•
•
Term to know: SUBDUCTION means
the crust is SINKING!
Three types of convergent
boundaries:
1. Ocean/Ocean = TRENCH
2. Ocean/Continental = TRENCH
3. Continental/Continental = MOUNTAINS
Convergent Collision #1
(Oceanic/Oceanic)
One of the plates will SINK (subduction!)
and form a TRENCH. Magma rises and
forms and island arc of volcanoes.
Convergent Collision #2
(Oceanic/Continental)
• The oceanic plate sinks (subduction!)
below the continent and the continental
plate slides over the top of the oceanic
plate. Forms a TRENCH.
Subduction Zone
Convergent Collision #3
(Continental/Continental)
• Both continental plates collide and rise up
forming MOUNTAINS. (Ex. Himilayas)
Divergent Boundaries
• Two plates pull apart forming a rift valley in
Rift Valley
the middle.
• Sea-floor spreading is created by a
divergent boundary.
Mid Ocean Ridge
Click Here to see Divergent Boundaries in motion!!!
When the divergent
boundary is on land .
There is a HUGE
rift valley in east
Africa called the
Great Rift Valley
Transform Boundaries
• Plates slide past each other in a
side to side motion. (Ex. San
Andreas Fault)
This fence used to line up!!
Before the 1906 Earthquake in
California
San Andreas Fault
WHY do the plates move?
…CONVECTION CURRENTS in the
mantle…Hot rock (less dense) rises to the
surface, cools (more dense), and sinks
back to the mantle.
HOT
MOLTEN
ROCK
RISES
COOL
MOLTEN
ROCK
SINKS
Convection Currents
Less
More
More
=
Dense
Less
=
Dense
More matter
Less matter
Rise
Sink
Same
Volume
Same
Volume
=
Less
Dense
=
More
Dense
Less matter
More matter
Less
Rise
More
Sink
Convection
Currents
Cools off!
= more dense
= fall to the
bottom
Hot!
= less dense
= rise to the
top
See Animation:
http://education.sdsc.edu/optiputer/flash/co
nvection.htm
REVIEW BOUNDARIES!