Plate Tectonics:

1. Plate Tectonics: Was Wegener crazy or did we just move a little bit? David Crewes CEP 811

2. Navigation Instructions: • The following slide show is brought to you by the Earth Science HSCE’s of the state of Michigan, and will assist each of you in reviewing for the material in Chapter 17 covering plate tectonics. • There will first be a brief review of the more important topics, then the quiz that follows will allow you to gauge your own retention of the class material. • You will notice several buttons on the bottom of each slide. They look like this: • These will take you to the previous slide, the next slide, or back to the first slide. • Some slides won’t have any buttons, but they will have some sort of question. Pick the correct answer, and you will move on to the next slide. Incorrect answers will display some pertinent information on the topic, then the question will be displayed again until the correct answer is chosen. • That’s pretty much it. Enjoy your review! CLICK HERE FOR A SECRET HINT! P.S. – You might want to try to remember which questions you answered incorrectly. You might see them again very soon!

3. CONTINENTAL DRIFT: • Alfred Wegener first supported early mapmakers ideas that the continents fit together like tiny puzzle pieces • His continental drift theory stated that the Earth’s continents were once all connected in a single landmass called Pangaea, and that when they inevitably split, they continued to drift apart to where they are today. • Wegener used the following evidence to support his theories: • Similar rock type and ages on different continents • Glacial scaring on continents that are too warm for the existence of glaciers. • Coal deposits on continents that are too cold to sustain the environment that would produce coal deposits • Similar fossils found on continents that are separated by vast oceans. • Unfortunately, Wegener couldn’t explain how the continents moved or what caused their motion, so his ideas were often rejected.

4. SEAFLOOR SPREADING: • Sonar and magnetic studies of oceanic rock led to theories of seafloor spreading • New ocean crust is formed at ocean ridges and destroyed at deep sea trenches • Magnetic patterns on the seafloor are symmetric in relation to ocean ridges, indicating that ocean crust on either side of the ridge is moving away from the ridge at essentially the same rate • Continual feeding of magma into the ridge causes the ridge to grow, and more seafloor to be produced • Continents were just along for the ride, floating on a sheet of moving crust • This concept answered the how question of continental drift, but the why was still a mystery

5. PLATE TECTONICS: • The earth’s crust and rigid upper mantle are broken into enormous slabs called plates (12 major, several minor) • Interaction at plate boundaries as they move

6. Divergent Boundary • 2 plates that are moving apart – most found on the seafloor, as ocean ridges • New crust formation • Increased seafloor basin • Those not on the seafloor are called Rift valleys (east Africa) formed from a magma dome

7. Convergent Boundary • Two plates moving toward one another • Three different types based on the types of plates converging (Click on each to see illustration) If your are ready for the big picture, click here!!! Oceanic - Oceanic Oceanic - Continental Continental – Continental

8. Transform Boundary • Two plates slide horizontally past each other • Releases massive amounts of energy when plates do finally let go • Leads to deformed and fractured crust rather than uplift and subduction • Characterized by long (100 km) fault lines with shallow earthquakes • San Andreas Fault in California is infamous for numerous earthquakes along it’s boundary

9. Oceanic – Oceanic Convergence • One plate descends under the other in a process called subduction • Features formed as the dense basaltic crusts come together are an oceanic trench, an island arc, or a rift valley • The subducted plate is recycled as it melts again to form magma • The re-melted magma comes to the surface and cools forming the aforementioned sea volcano and island arc

10. Oceanic – Continental Convergence • As the oceanic and continental slab converge, the less dense continental rides up on the other and forces the oceanic to subduct • Produces mountain volcanoes at or near the continental plate • Leads to the formation of an off-shore deep sea trench caused by the subduction of the ocean floor

11. Continental – Continental Convergence • When neither continental crust will give, plates crash into each other • Due to their relative buoyancy, they are both thrust upward creating folded mountains Hey!! Nice Mountains!!

12. Mantle Convection CLICK ME • Put all the previous features together and you have the process for plate tectonics via convection currents • This is also called Ridge - Push Slab - Pull

13. QUIZ TIME!!!

14. What is the name of this ancient continent before it broke apart? A) Pancreas B) Gondwanaland C) Pangaea D) Pluto

15. Sorry!!! • Nice try! • Try to remember what we talked about in class. • If you would like a hint, click the “HINT” button, otherwise click the back button to try again HINT

16. CONTINENTAL DRIFT: • Alfred Wegener first supported early mapmakers ideas that the continents fit together like tiny puzzle pieces • His continental drift theory stated that the Earth’s continents were once all connected in a single landmass called Pangaea, and that when they inevitably split, they continued to drift apart to where they are today. • Wegener used the following evidence to support his theories: • Similar rock type and ages on different continents • Glacial scaring on continents that are too warm for the existence of glaciers. • Coal deposits on continents that are too cold to sustain the environment that would produce coal deposits • Similar fossils found on continents that are separated by vast oceans. • Unfortunately, Wegener couldn’t explain how the continents moved or what caused their motion, so his ideas were often rejected.

17. YES!!!!! • Nicely done! • Gondwanaland was only the southern continents, Pangaea was all of the continents together • Eventually we will all be stuck together again. Not to worry, won’t happen for another 200 million years or so • Ready for the next question?

18. Why was glacial evidence and coal bed evidence important for Wegener's theories? A) Coal is an important natural resource, and takes a long time to make. • Glaciers haven’t been around for a long time, so that proves the continents are very old. • The existence of coal and glaciers on continents that have opposite climates for them, proves that they have traveled over the years. • All of the above

19. Sorry!!! • Nice try! • Try to remember what we talked about in class. • If you would like a hint, click the “HINT” button, otherwise click the back button to try again HINT

20. CONTINENTAL DRIFT: • Alfred Wegener first supported early mapmakers ideas that the continents fit together like tiny puzzle pieces • His continental drift theory stated that the Earth’s continents were once all connected in a single landmass called Pangaea, and that when they inevitably split, they continued to drift apart to where they are today. • Wegener used the following evidence to support his theories: • Similar rock type and ages on different continents • Glacial scaring on continents that are too warm for the existence of glaciers. • Coal deposits on continents that are too cold to sustain the environment that would produce coal deposits • Similar fossils found on continents that are separated by vast oceans. • Unfortunately, Wegener couldn’t explain how the continents moved or what caused their motion, so his ideas were often rejected.

21. Correct! • Super job! • Since glaciers and coal deposits can only occur in extremely specific climates, the only way for these two continents to have exactly opposite conditions from what they have currently is that they have migrated due to plate tectonics.

22. Study the map below and explain why the Pacific seafloor has a larger red area (younger rock) than the Atlantic seafloor? A) It is hotter. B) More earthquakes, therefore more friction. C) More resistance in the Atlantic basin. D) The seafloor in the Pacific is spreading faster.

23. OOPS!!! • Valiant effort! • Try to remember what we talked about in class. • If you would like a hint, click the “HINT” button, otherwise click the back button to try again HINT

24. SEAFLOOR SPREADING: • Sonar and magnetic studies of oceanic rock led to theories of seafloor spreading • New ocean crust is formed at ocean ridges and destroyed at deep sea trenches • Magnetic patterns on the seafloor are symmetric in relation to ocean ridges, indicating that ocean crust on either side of the ridge is moving away from the ridge at essentially the same rate • Continual feeding of magma into the ridge causes the ridge to grow, and more seafloor to be produced • Continents were just along for the ride, floating on a sheet of moving crust • This concept answered the how question of continental drift, but the why was still a mystery

25. Yup, you got it! • Some parts of the Pacific seafloor are spreading at twice the rate the Atlantic is. • This also creates oceanic trenches that are very deep due to the subduction rates of the ocean floor. • Marianas Trench is one of them • Next question!!!!!!!

26. With the big picture in mind, what plays the biggest part of keeping the movement of the plates going? A) Upwelling or Ridge - Push B) Subduction or Slab – Pull C) Gravity D) All of the choices, or equal forces producing movement

27. Bummer!!! • Keep trying! • Try to remember what we talked about in class. • This is a thinker, no hint available. Think about the forces involved and what keeps them going.

28. That was great!! • Another correct answer, your pretty good at this. • The forces of the magma pushing the ridge apart and pulling the slab down are a given. However, the force of gravity is probably the largest force involved due to the large masses involved, but it’s a tough call. We will leave it to the Scientists with all that time on their hands. We have things to do. • ON WITH THE TEST!!!!!! CLICK HERE