Download Plate Tectonics

Plate Tectonics
Chapter 9.2 – 9.3
Plate Tectonics
• Proposed in 1965 by Tuzo Wilson = combination of
Wegener & Hess’s ideas.
• Convection Currents move the lithospheric plates
causing geologic activity – (mountain building,
volcanic eruptions and earthquakes)
Convection Currents
Upper Mantle - COOLER
Lower Mantle - HOTTER
The magma in the lower
mantle is warmer. It
expands, becomes less
dense and rises.
When it reaches the upper
mantle it cools, contracts,
becoming more dense and
sinks.
This constant rise and fall of
magma causes the
convection currents that drive
plate tectonics.
The crust plates ride along
on top of these convection
currents.
Earth Layers
1. Lithosphere: the
ridged crust and
upper part of the
mantle.
- Cool, hard and solid
- Breaks very easily
2. Asthenosphere: the
lower mantle
– Hot and plastic-like
– Flows easily
• The lithosphere is broken up into 7 large plates
and 20 smaller plates
• The plates have boundaries
• As they move they affect one another.
Convergent Boundary
Divergent Boundary
Transform Boundary
Plate Tectonics Reference Table
You need to know how to read
this table!!
Pacific Plate – Where the Action is!
RING OF FIRE!!
Hawaii
Hawaii is a chain of
islands made from an
underwater volcano.
Yet Hawaii is NOT on a
plate boundary.
How was Hawaii
created?
Hawaiian Hot Spot
• Hawaii is in the middle
of the Pacific Plate
• Not on a boundary.
Magma Rises under Hawaii
•Hot spot is located
in the mantle and
does not move
•The Pacific Plate
moves NW over the
hot spot forming a
line of volcanoes.
Plate Boundaries!!
Divergent
Convergent
Transform
Divergent Boundary
• When Plates Divide or Separate
Step 1 – Rift Valley
• Magma pushes up cracks in the crust
• Convection causes the separated plates to
move and form a rift valley.
Step 2 – Add Water
• The valley widens and begins to be filled with
water. (Red Sea)
Step 3 – Ocean Formed
• Eventually an
ocean forms
– At the rate of 6
cm per year
Ex. Mid Atlantic
Ridge
Divergent Boundaries Map
Transform Boundary
• Two Plates slide past
each other
• Also called strike-slip
boundary
• Example: San Andreas
Fault in California
San Andreas Fault
• The Pacific Plate
moves North
• The North American
Plate moves South
San Andreas Fault
• Causes stress that
leads to Earthquakes
in California
Convergent Boundaries
• 2 Plates colliding into
each other.
• Example: Himalayan
Mountains formed when
India collided with Asia
• We will Continue these notes tomorrow!!! There is
a lot to know about Convergent Boundaries!