The Theory of Plate Tectonics

1. The Theory of Plate Tectonics Concepts: • What is the theory of plate tectonics? • What are the three types of plate boundaries? Terms: • J. Tuzo Wilson • Plate • Scientific theory • Plate tectonics • Fault • Divergent boundary • Rift valley • Convergent boundary • Transform boundary

2. J. Tuzo Wilson and Plates • A Canadian scientist, J. Tuzo Wilson, observed that there are cracks in the continent similar to those on the ocean floor. • In 1965, Wilson proposed a new way of looking at these cracks. • According to Wilson, the lithosphere is broken into separate sections called plates.

3. Lithospheric Plates

4. The Theory of Plate Tectonics • The theory of plate tectonics explain the formation, movement, and subduction of Earth’s plates.

5. How do the plates move? • The theory of plate tectonics states that pieces of Earth’s lithosphere are driven by convection currents in the mantle. • As the plates move, they collide, pull apart, or grind past each other producing spectacular changes in Earth’s surface. • Volcanoes, mountain ranges, and deep ocean trenches • The plates move very slow about 1-24 centimeters a year. • About as fast as your fingernails grow. • They have been moving for tens of millions of years.

8. As we review each plate boundary, complete a tree map and include the following: • Focus Questions: • Plate Boundary • Which direction are the plates moving at these boundaries in relationship to each other? • What action occur at each location/type of plate boundary? • Whatformsbecause of these actions? • Examples

9. Tree Map • Plate Boundary Location Location Plate Movement Arrows Action Action Examples Definition Examples

10. Types of plate boundaries • Divergent plate boundary • Ocean: Mid Oceanic Ridge • Land: Continental Rift zone • Convergent plate boundary • Oceanic-oceanic convergence – SubductionTrench • Continental-continental convergence – No Subduction - Mountains • Oceanic - continental convergence – Subduction Trench • Transform plate boundary • Earthquakes • Crust is neither created nor destroyed.

11. Divergent plate boundaries A place where two plates move apart, or diverge

12. Ocean Mid-Ocean Ridge E.g. Mid-Atlantic ridge is a result of sea floor spreading new basaltic magma rises to the surface along the ridge forming new oceanic crust.

13. Thingvellir Rift Valley http://epod.usra.edu/blog/2010/08/mid-atlantic-ridge-in-iceland.html Slicing through the center of Iceland is the Mid-Atlantic Ridge. This is the boundary between theNorth American and Eurasian tectonic plates ThingvellirNational Park, in southwestern Iceland, is one of the few spots in the world where an underwater ridge rises above the water surface. Iceland is one of the most geologically active places on Earth with more than 15 volcanoes that have erupted in the last century.

14. Land • Rift valleysmay increase in size till water fills them to form a Sea • The Red Sea and the Gulf of Aden were once rift valleys. Mt. Kilimanjaro These rift valleys often have volcanoes lining them. Great African Rift Valley

15. The formation of the Atlantic Ocean

16. Divergent Plate Boundaries In the Ocean • Ridge • Action: oceanic plates move apart • Sea floor spreading • Mid-Ocean Ridge • Example: Mid Atlantic Ridge • Longest mountain Range On Land • Rift • Action: Continental crust pull apart • Examples: Iceland, Great Rift Valley in East Africa • Oceans and Seas form • Example: Atlantic Ocean and Red Sea • Volcanoes • Example: Mt. Kilimanjaro

17. Tree Map Divergent Plate Boundary Plate Movement Ocean: Ridge Land: Rift Action: Sea-floor spreading Example: Mid Atlantic Ridge Oceans and Seas form: Examples: Atlantic Ocean and the Red Sea Action: Continental crust pull apart Examples: Iceland, Great Rift Valley in East Africa Oceans and Seas form Example: Atlantic Ocean and Red Sea Volcanoes Example: Mt. Kilimanjaro A place where to plates move apart, or diverge

18. Convergent Plate Boundaries The place where two plates come together, or converge. Three types of convergent plate boundaries: • Ocean crust to ocean crust collision • Ocean crust to continental crust collision • Continental crust to continental crust collision

19. Tree Map • Name of plate boundary • Draw arrows to indicate direction the plates move in relationship to each other. • Create a Tree map of the 3 types of convergent boundaries, the events that occur there, and an example of each occurrence. i.e. action, formations, examples • Compare the items in your map, which convergent boundary type does NOT result in volcanoes? Why?

20. Mt. Hood

22. Aleutian Islands Trench Island arc

23. Oceanic - continental convergence E.g. Andes mountains The forces of plate tectonics are responsible for the formation of the Andes. The Nazca plate and a part of the Antarctic plate have been subducting beneath the South American plate, which is a process that continues today and causes earthquakesandvolcanic eruptions in the region http://www.windows2universe.org/geography/andes.html

25. Quick Review

27. The sub-continent of India has collided with the Eurasian continent to form the Himalayas

28. Types Convergent plate boundaries Oceanic-oceanic convergence Islands Japan, Aleutian Islands Volcanoes- Mt Pinatubo Trenches Earthquakes Oceanic - continental convergence Volcanoes - Andes, Cascades Trenches Earthquakes Continental-continental convergence No volcanoes Mountain building - Himalayas

29. Convergent Boundaries • 3 types of convergent boundaries • Ocean to ocean crust • Crust melting forms volcanic island arc, ex Aleutian Islands • Volcanoes – Philippines- Mt Pinatubo • Subduction forms trench • Ocean to continental crust • Crust melting forms volcanic mountain ranges, ex Andes, cascade range, Mt Rainer, Mt Baker • Subduction zones forms, trenches, • Ocean crust denser than continental crust. • Ocean crust slides/subducts under the continental crust • Continental to continental crust • No melting of crust = no volcanoes • No subduction • Folding of crust = Non-volcanic mountains are formed -Example Mt Everest

30. Tree Map Convergent Plate Boundaries • Continental to continental crust Ocean to ocean crust Ocean to continental crust Crust melting forms volcanic mountain ranges, ex Andes, cascade range, Mt Rainer, Mt Baker Subduction zones forms trenches Ocean crust denser than continental crust. Ocean crust slides/subducts under the continental crust Crust melting forms volcanic island arc, ex Aleutian Islands Volcanoes – Philippines- Mt Pinatubo Subduction forms trenches No melting of crust = no volcanoes No subduction Folding of crust = Non-volcanic mountains are formed -Example Mt Everest

31. Transform Boundary A place where two plates slip past each other, moving in opposite directions

32. North American plate Pacific plate

33. San Andres Fault

34. Earthquake in action • http://www.classzone.com/books/earth_science/terc/content/visualizations/es1005/es1005page01.cfm?chapter_no=visualization

35. Transform plate boundary • Action: Earthquakes • Forms: fault • Example: San Andres fault • No crustal melting = No volcanoes

36. Transform Boundary • Draw arrows to indicate direction the plates move in relationship to each other. • Name a location of a transform boundary. • Name the event that occurs at transform boundaries. • Could a volcano erupt in Los Angeles? Why or why?

37. Transform Boundary Crust is neither created nor destroyed Forms Direction Faults No crustal melting = No volcanoes Earthquakes Is a place where two plates slip past each other Example: San Andres fault