By the end of these notes you should be able to:

1. By the end of these notes you should be able to: 1. Draw & describe the MOTION at each of the 3 types of boundaries 2. Determine the boundary type based on geologic features such as • Volcanoes, • Ridges, • Rifts, • Subduction Zones, • Trenches, • and Mountains.

2. Directions • Read each slide • When there are questions, answer them before clicking on them. See how much you know! • Go to the links to view simulations, videos, etc.

3. Our Changing Earth San Francisco City Hall after the earthquake of April 18, 1906 Magnitude of 7.8 on the Richter scale. Between 3,000 to 6,000 dead, and 225,000 to 300,000 left homeless.

4. Lithosphere Asthenosphere Mantle Outer Core Inner Core Plate Tectonics The Earth’s surface is broken into 13 pieces called plates. They are composed of the crust and the upper part of the Earth’s mantle layer. I.A. The crust and lithosphere consist of cooled, solid rock. The asthenosphere is the partially melted, molten, upper part of the mantle. I.B.

5. Lithosphere Asthenosphere Mantle Outer Core Inner Core Plate Tectonics The crustal plates of the Earth glide around the asthenosphere like pucks on a hockey rink. One theory of how this works is that convection currents of hot, molten rock in the mantle move the plates. I.C.1. As hot, less dense magma rises, it replaces colder, more dense magma which falls back to the core to be reheated and continue the cycle. Another theory is based on density…as the plates get older, rockier, and heavier, they begin to sink back down into the mantle…moving as they do.I.C.2.

6. What do the convection currents in the Mantle look like? 2. How can they move the Lithosphere above it? Wheels As the convection currents spins it moves the plate above it just like the wheels on a conveyer belt.

7. Transform Boundaries Draw arrows on diagram to show motion As the plates move, they interact with each other in one of three ways at boundaries where they meet. At a transform boundary, plates slide past each other. II.A. As this happens, the release of energy due to friction causes earthquakes, but earthquakes can occur at any type of boundary. II.B. The San Andreas Fault in California is an example and was responsible for the great San Francisco earthquake of 1906. III.C.

8. Transform Boundaries Part of California is moving North, while part of California is moving South. With Los Angeles extremely close to and San Francisco directly on the fault line, there is a great potential for disaster.

9. The Mid-Atlantic Ridge at the bottom of the Atlantic Ocean is an example. III.C. Divergent Boundaries Draw arrows on diagram to show motion At a divergent boundary, plates spread apart from each other. III.A. Draw your divergent boundary now. Then we will show you some examples. Be sure to label the lithosphere and asthenosphere! At a ridge or rift, new rocks form where magma rises up and cools. This pushes the older rocks aside. III.B.

10. Divergent Boundaries The African Rift Valley is another example. East Africa is separating from West Africa. III.C. The Mississippi River Basin in North America is a failed attempt of a divergent boundary in the past. III.C.

14. Iceland is important because. . . • A team of scientists, led by Charles Wyville Thomson, discovered a large rise in the middle of the Atlantic (like Iceland) while investigating the future location for a transatlantic telegraph cable in 1850. • From this it was inferred that there was a split separating the ocean floor which we call the mid-atlantic ocean ridge today.

15. These people are walking directly on the divergent boundary where the plates are separating • Add Iceland as example #4, and name the 2 plates.

16. Why is Iceland green when it is just as far north as Greenland (which is frozen)? • Did you answer? • Warm Gulf Stream flows by it. • Iceland was created by the hot lava that flows out of the mid-atlantic ridge. Which continues to heat it.

17. Convergent Boundaries Label & Draw arrows on diagram to show motion At a convergent boundary, two plates come together and collide. IV.A. The heavier, denser plate is forced downward and remelts into magma. This newly formed magma is the lava source for volcanoes which are frequent here. Areas where this occurs are called subduction zones. IV.B. If the two plates are equally dense, the crust is forced upwards resulting in mountain ranges.

18. Is Oceanic or Continental Crust Denser? • Oceanic is MUCH Denser If Oceanic is denser, what will happen when it collides with continental crust? • Oceanic will sink under the less dense continental.

19. Why does land crumple up and form mountains when 2 continental crusts collide? • Continental crust is not very dense, and since both are the same density they just crumple up into mountains.

20. What do you think will happen when 2 oceanic crusts collide? • Since they are both so dense they push each other downward into a Trench

21. Convergent Boundaries Much of the Pacific plate is a convergent boundary. It is responsible for some geologic extremes… What 2 plates surround the Marianas Trench? Phillipine There are lots of volcanoes around the Pacific plate due to the subduction zones. Pacific …like the Marianas Trench. It is the deepest point on Earth (7 miles down). It is at the bottom of a subduction zone off the coast of the Philippines. IV.C.

22. Convergent Boundaries …and also Mt. Everest. It is the highest point on Earth (5.5 miles up). It is the result of the Indian plate colliding with the Eurasian plate. IV.C.

23. Convergent Boundaries Although earthquakes can happen at any type of boundary, volcanoes are mainly found near convergent boundaries. Why? V. Volcanoes form because pressure builds up under surface due to subduction adding mass. Earthquakes are caused when any plate moves in any direction.

24. Watch the convection currents in the mantle video

25. What type of boundary is this? What type of boundary is this? What type of boundary is this? What type of boundary is this? Boundaries Check Up Transform Divergent Convergent Divergent

26. Lets see what you know! Can you. . . Use hand motions to show & describe the MOTION at each of the 3 types of boundaries Divergent Transform Convergent Plates move apart Plates slide side by side Plates collide

27. By the end of these notes you should be able to: Determine the boundary and type of crust, based on geologic features such as • Volcanoes, • Ridges, • Rifts, • Subduction Zones, • Trenches, • Mountains. Convergent between Oceanic & Continental Divergent boundary between oceanic & Oceanic Divergent boundary between continental & continental Convergent boundary between oceanic & Continental Convergent boundary between oceanic & Oceanic Convergent boundary between Continental & Continental

29. Click here to Test your skills

30. http://www.learner.org/interactives/dynamicearth/slip2.html http://geology.com/nsta/ http://www.mrenns.com/Docs-PowerpointsWeb/Ppoint-PlateBoundaries.pdf The End