Plate Tectonics Chapter 9.2 – 9.3
Jan 21, 2016
Plate TectonicsChapter 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 Layers1. 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!!
HawaiiHawaii 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!