1. Warm Up #11
What is plate tectonics?

2. Lesson 3: The Theory of Plate Tectonics
Ch. 2 Plate Tectonics
Lesson 3: The Theory of Plate Tectonics

3. Essential Questions What is the theory of plate tectonics?
What are the three types of plate boundaries?
Why do tectonic plates move?

4. Can you determine density by observing buoyancy? ACTIVITY
Density is the measure of an object’s mass relative to its volume. Buoyancy is the upward force a liquid places on objects that are immersed in it. If you immerse objects with equal densities into liquids that have different densities, the buoyant forces will be different. An object will sink or float depending on the density of the liquid compared to the object. Earth’s layers differ in density. These layers float or sink depending on density and buoyant force.
Place 4 test tubes in a test tube rack
Add water to 1 test tube till it’s about ¾ filled
Do the same with vegetable oil and glucose syrup and have 1 test tube empty
Drop a bead in each tube. What do you notice?
How can you determine which liquid has the highest density?

5. Plate Tectonics Theory
Plate tectonics – Earth’s surface is made of rigid slabs of rock, or plates, that move with respect to each other
This suggests Earth’s surface is divided into large plates of rigid rock, which move over Earth’s hot and semi-plastic mantle
Can you predict where volcanoes are located?

6. Plate Tectonics Theory
Plate tectonics – Earth’s surface is made of rigid slabs of rock, or plates, that move with respect to each other
This suggests Earth’s surface is divided into large plates of rigid rock, which move over Earth’s hot and semi-plastic mantle
Can you predict where volcanoes are
located?

7. Tectonic Plates What is the Earth’s outermost layers called?
What is the asthenosphere?

8. Tectonic Plates What is the Earth’s outermost layers called?
Cold and rigid compared to the layers within Earth’s interior
Lithosphere – cold and rigid outermost rock layer
Made up of crust and solid, uppermost mantle
Thin below mid-ocean ridges, thick below continents
What is the asthenosphere?
So hot, it behaves like a plastic material
Enables Earth’s plates to move due to hotter, plastic mantle material beneath them can flow
Interactions between lithosphere and asthenosphere help to explain plate tectonics

9. Plate Boundaries What is a plate boundary?
Wat are the 3 types of plate boundaries?

10. Plate Boundaries What is a plate boundary?
A place where 2 or more plates interact
What are the 3 types of plate boundaries?
Divergent, transform, and convergent
Take a sheet of paper and fold it into 3rds
Compare the 3 plate boundaries
Include the type, movement that occurs, and
the results
Don’t just copy but put in your words

11. Plate Boundaries
Divergent Plate Boundaries – forms where 2 plates separate
Mid-ocean ridges and rift valleys form
Transform Plate Boundaries – forms where 2 plates slide past each other
Earthquakes form
Convergent Plate Boundaries – form where 2 plates collide
Subduction – denser plate sinks below the more buoyant plate
Ocean trench formed by oceanic plate subducting under continental plate forming volcanoes on edge of continent
Older oceanic plate subducts under younger oceanic plate creating deep ocean trench and volcanoes to create island arc
2 continental plates collide forming mountains

12. Plate Boundaries

13. Movement of Plate Boundaries CLASSWORK
Earth’s surface is broken into 12 major tectonic plates. Wherever these plates touch one of four events occurs. The plates may collide and crumple or fold to make mountains. One plate may subduct under another, forming volcanoes. They may move apart and form a mid-ocean ridge, or they may slide past each other causing an earthquake. This investigation models plate movements.
You will need 2 pieces of graham cracker, some waxed paper, and frosting.
Turn to Pg. 66 in textbook
You must answer all questions in complete sentences on Pg. 67 to be turned in by tomorrow in class with your first and last name, section, and date.

14. Warm Up #12
What causes convection?

15. Evidence for Plate Tectonics
We can measure how fast continents move
Provides evidence for why earthquakes and volcanoes and other natural disasters occur

16. Plate Motion
Convection – the circulation of material caused by differences in temperature and density
Convection Currents DEMO
Place a beaker of water on a ring stand above a Bunsen burner (at one side of the beaker)
As water heats up add ice cubes to opposite side of beaker along with a few drops of food coloring
What do you notice?
How does this demonstrate convection currents?

17. Forces Causing Plate Motion
Basal Drag – convection currents in the mantle produce a force that causes motion
Ridge Push – rising mantle material at mid-ocean ridges creates the potential for plates to move away from the ridge with a force
Moves lithosphere in opposite directions away from the mid-ocean ridge
Slab Pull – a slab sinks, it pulls on the rest of the plate with a force
The slab is older, cold, and denser than surrounding mantle and will sink

18. A Theory in Progress
Several unanswered questions remain even though some have been answered
Why is Earth the only planet in the solar system that has plate tectonic activity?
Why do some earthquakes and volcanoes occur far away from plate boundaries?
What forces dominate plate motion?
What will scientists investigate next?

19. Why does the theory of plate tectonics continue to change?
Name the type of boundary between the Eurasian Plate and the North American Plate.
Name the type of boundary
between the Nazca Plate and
South American Plate.