In your own words describe Continental Drift Hypothesis How did Wegener support his hypothesis?

1. In your own words describe Continental Drift Hypothesis • How did Wegener support his hypothesis? • Why do you think he chose this type of information? • Why was the continental drift hypothesis rejected? • What is the difference between the Theory of Continental Drift and the Theory of Plate Tectonics? (c) McGraw Hill Ryerson 2007

2. III. Layers of the Earth • Crust • Mantle • Outer core • Inner core

3. Crust • Outermost layer, • relatively solid, brittle rock layer Continental crust • approx. 50 km thick • made from less dense type of rock called granite Oceanic crust • approx. 10 km thick • made from dense rock called basalt

4. Mantle • Thickest layer: 2900 km thick • Iron, magnesium and silicon • Upper Mantle: solid, more cool and brittle • Lower Mantle: molten rock, solid, dense • Flows like toothpaste

5. Outer Core • 2200 km thick • Made up of liquid iron and nickel Inner Core • 1200 km thick • solid iron and nickel (due to tremendous pressure) • Extremely hot 5,500°C

6. Tectonic Plate Layers LITHOSPHERE: • Outer layer of rock composed of crust and part of upper mantle. • Makes up the tectonic plates • 65-100 km thick

7. ASTHENOSPHERE: • Makes up molten layer beneath plates • Lower Mantle • So hot it behaves like plastic, less rigid, flows like toothpaste

8. Tectonic Plates • 12 major plates and many smaller ones. • Oceanic Plates – contain dense basalt • Continental Plates – granite • Interactions between lithosphere and asthenosphere help explain plate tectonics because the hotter, plastic mantle material (asthenosphere) beneath can flow enabling plates (lithosphere) to move.

9. Questions • Tectonic plates are composed of which parts of Earth’s layer? • What are two types of tectonic plates? • Describe two features of each.

10. V. Plate Interactions : Boundaries • Plate boundaries are marked by earthquakes, volcanoes, mountain ranges and ocean trenches • There are three main types of plate boundaries: • Divergent • Convergent • Transform

11. Melting crust rises beneath the subduction zone, forming volcanoes parallel to the plate boundary; • trenches are found beneath the ocean where the oceanic crust subducts;

12. 1) Divergent Boundaries • When two plates separate and create new oceanic crust. • Sea floor spreads along a mid-ocean ridge. • Can also occur in middle of continents (continental rifting) • Mid-Atlantic ridge – • largest mountain range

13. Divergent Boundaries • Mid-Atlantic ridge

14. Divergent Boundaries Endeavour hydrothermal vents were created as the Juan de Fuca plate moves away from the Pacific plate

15. Diverging Plates • Diverging plates at the East African Rift are slowly breaking Africa into pieces

16. Convergent Boundaries • Where two plates collide • Denser crust eventually goes below the less-dense crust (subduction), causing deep sea trenches to form • Volcanoes and Mountains form, earthquakes common • variable results depending on the plates involved

17. a) Continental-Oceanic Plates • When dense oceanic plates collide with continental plates, the oceanic plate will sink under the continental plate and be pushed into the mantle (subducted). • Continental crust is less densethan oceanic crust and never subducts

18. Cone-shaped volcanoes of West Coast of North America are result of oceanic –continental convergence between Juan de Fuca Plate (oceanic) and North American Plate (continental).

19. Cascade Mountain Range • Mount Garibaldi – result of the Juan de Fuca plate subducting under the North American plate • Mount Meager

20. c) Oceanic-Oceanic Plates • When two oceanic plates collide, usually one plate subducts beneath the other. • VolcanicIsland Arcs form above the non-subducting plate.

21. Islands of Japan and Indonesia and the Aleutian Island of Alaska

22. Pacific Ring of Fire

23. Pacific Ring of Fire • The Ring of Fire is a major area in the basin of the Pacific Ocean where a large number of earthquakes and volcanic eruptions occur. (c) McGraw Hill Ryerson 2007

24. c) Continental-Continental Plate Convergence • When continental plates collide, neither plate is dense enough to be pushed down, so the land buckles like a car hood in a car crash (“uplifting”), forming mountain ranges;

25. Himalayan Mountain Range • Himalayas formed from Indian continent colliding with Asian continent. • Continue to increase in elevation by several cm per year

26. 3) Transform Boundaries • Where two plates slide by each other • Results in frequent earthquakesand faults • Fault – breaks in rock layers due to movement on either side

27. 3) Transform Boundaries • First identified by Canadian geologist, John Tuzo Wilson. • Earthquakes are common at these boundaries • Oct 2012, an earthquake of magnitude of 7.7 originated from movement along the Queen Charlotte Fault.

28. Transform Boundary • San Andreas Fault

29. Plate Boundary Symbols

30. III. Plate Motion • Tectonic plates make up the lithosphere (crust and upper portion of mantle), which floats on the asthenosphere (molten, lower mantle). • Tectonic plates are all moving at the same time

31. III. Plate Movement • Variable temperature causes convection currents See pages 520 - 522 (c) McGraw Hill Ryerson 2007

32. Mantle Convection • Molten rock called magmain the mantle is heated up near the core of the earth and becomes less denseand buoyant. • Warmer, less dense material rises and cooler, denser material sinks, causing convection current. • As magma moves, it drags the tectonic plates above with it.

33. Rising magma pushes plates apart at spreading centers in oceans • Colder, dense magma near the surface sinks. • The rotation causes movement of the plates.

34. The Earth’s Temperature • As you go deeper into the Earth’s crust, the temperature increases about 1oC for every 40 m of depth • Beneath the crust, this temperature rise gradually slows, until a core temperature of about 7000oC is reached.

35. The Earth’s heat comes from: • radioactive element decay (uranium, potassium, thorium); • friction between rock masses in the crust and mantle; • heat left over from planetary formation.

36. Two other processes affecting plate movement Ridge Push – rising material spread out as it reaches the upper mantle. This cause the lithosphere to lift and push tectonic plates apart at divergent plate boundaries.

37. Slab Pull • Slab Pull – as the leading edge of a subducting plate sinks, it pulls the rest of the plate with it at convergent plate boundaries. Gravity and convection assist this movement.

38. Name and draw three main types of tectonic plate boundaries. • Why does subduction not occur at some kinds of tectonic plate boundaries? • Describe the process that results in a volcanic island arc. • Name a mountain range produced by continental-continental plate convergence.