Theory of Plate Tectonics Ch.7.3 (New Book) p.194 Theory of Plate Tectonics Let’s check Friday’s classwork! 1.D 2. a 3.b 4.b 5. A 6. d 7. c 8.ab 9. B 10. d 11. b 12. b 13. B 14. b 15. a 16. d 17. Ab 18. c 19.d 20. c 21. C 22.a 23.a 24. B 25. C 26. a 27.d

Let’s Read more about Plate Tectonics! p. 194-195 Then: Answer in your IAN, how are tectonic plates like ice cubes in a punch bowl? How many plates are covered in BOTH land and water? How is plate movement different than continental drift?

The Theory of Plate Tectonics Objectives: (copy me down in your IAN) What is plate tectonics? Where does the FORCE come from to move the tectonic plates? Describe the three types of plate boundaries. 4. Review, what are subduction zones?

Open to p. 194 (New Book) and finish drawing your plate maps in your IAN. Ocean floor blue, land green or brown, and tectonic boundaries in RED!

Oceanic and Continental Crusts

Let’s review: Tech Terms: (copy these down) plates – separate sections of the lithosphere. plate tectonics – a geological theory that states that pieces of the Earth’s lithosphere are in constant, slow motion, driven by convection currents in the mantle.

What are Three Possible Driving Forces of Plate Tectonics?

Now let’s create new maps in our IAN. Take out the new map from your blue tub. Using p. 194. complete the instructions on this new map. An example picture is on the next page!

The 10 top Tectonic Plates!

These plates are created by 3 These plates are created by 3. faults – breaks in Earth’s crust where plate boundaries form. The Theory of Plate Tectonics: What are the boundaries and how do they move? Read aloud p. 202-203 and discuss.

Tech terms, copy these down! 4) convergent boundary – the place where two plates come together, or collide. (the density of the plates dictates which one comes out on top). Oceanic crust (basalt rock) is more dense Continental crust (granite rock) is less dense

Subduction zones occur at convergent boundaries and create trenches

Examples: 5. subduction – when the ocean floor sinks beneath a deep ocean trench and gets swallowed by the mantle. Sea Floor Spreading& Subduction: Plate Tectonics inside the mantle again! (2 min)

6. deep ocean trench – this forms from subduction (the oceanic crust bends downward forming a deep underwater canyon on the ocean floor).

deep ocean trench examples

deep ocean trench close to home

7. divergent boundary – the place where two plates move apart, or dive away (most occur at the mid-ocean ridge from seas floor spreading). 8. Example: Sea floor spreading- the process that adds new material to the ocean floor at the mid-ocean ridge..

Divergent bounderies… 8. Example: rift valley – develops on land, where two plates diverge. Read and discuss the picture at the bottom of page 202-203.

3 “Big Effects” of Subduction and Seas floor Spreading: 9. Evidence of Plate tectonics: Sea-floor spreading and subduction can change the size and shape of the oceans. The Pacific Ocean, aka The Ring of Fire, has lots of subduction zones, thus it is getting smaller. The Atlantic Ocean is expanding.

10. transform boundary – a place where two plates slide past each other in opposite directions.

Transform boundaries do not create landforms Transform boundaries do not create landforms. They do, however, destroy land!

See the offset from the Transform boundary?

So what will happen as these plates in the ocean floor continue to spread? Earth 100 Million Years from now Convection Currents in the Earth. One more time, a different way! Plate tectonics on a cocoa earth - YouTube

Further Evidence for Sea-Floor Spreading: 11. Magnetic Reversals- Molten rock at the mid-ocean ridges contains tiny grains of magnetic minerals. These mineral grains contain iron and are like compasses. They change Earth’s magnetic poles!!

The iron mineral grains align with the magnetic field of the Earth The iron mineral grains align with the magnetic field of the Earth. When the molten rock cools, the record of these tiny compasses remains in the rock. This record is then carried slowly away from the spreading center of the ridge as sea-floor spreading occurs. When the Earth’s magnetic field reverses, the magnetic mineral grains align in the opposite direction.

Magnetic reversals in oceanic crust are shown as bands Magnetic reversals in oceanic crust are shown as bands. Light blue is when the poles have normal polarity. Dark blue indicates reverse polarity.

The new rock records the direction of the Earth’s magnetic field The new rock records the direction of the Earth’s magnetic field. As the sea floor spreads away from a mid-ocean ridge, it carries with it a record of magnetic reversals. This record of magnetic reversals was the final proof that sea-floor spreading does occur.

The polarity of Earth’s magnetic field changes over time.

Magnetic Reversal videos: Sea Floor Spreading Demo:  

3 Types of Boundaries have different effects. What are they? With your hands, show me the 3 types of boundaries! Stand and Do! Now let’s illustrate it!