1. Unit 1: Landforms September 2014

2. What is Geography? Geography is the study of how the earth works and how people interact with it. We are first concerned about understanding the forces that shaped the earth’s surface

3. What shaped the Earth’s Surface?

4. Earth’s Structure –A look Inside Inner Core and Outer Core Inner core Outer core

5. Mantle

6. Mohorovicic Discontinuity

7. Asthenosphere

8. Lithosphere

9. Earth’s Structure (cont’d) Review video: http://www.youtube.com/watch?v=3MFr2cC3 erk http://www.youtube.com/watch?v=3MFr2cC3 erk

10. Landforms Plates:The earth’s crust is made up of different tectonic plates

11. How Compressional and Tensional Forces are Created Plate Tectonics: The movement of the earth’s plates. Includes both compressional and stretching (tensional) forces Compression Stretching/Tensional

12. Compressional Processes Compressional Force: Parts of the earth’s crust pushing toward each other, causing colliding parts to rise, fall and buckle underneath.

13. Subduction zone:Place where two tectonic plates collide. The more dense plate goes under, or subducts, to the other

14. A Subduction Zone

15. Tensional Force: – A stretching force in the earth’s surface which may cause faulting. Plates break apart and move away, or past, each other. – This will often cause a trench as one plate moves downward. Ridges sometimes form as the magma rises between the plates

17. Relating Tectonic Plates to Compressional and Tensional Forces Compressional Forces: Plates (arrows) colliding Tensional Forces: Plates (arrows) moving away from each other

18. Wegener’s Theory of “Continental Drift”: – Explains the movements of tectonic plates – Plates carried by hot magma (Proven by Tuzo Wilson) – All continents were once joined together called “Panagaea”. – They broke into two sections about 200 million years ago. These two sections broke pieces. – They drifted to their present locations. Based upon fossils and rock formations we know today

19. Panagaea

20. Wegener’s Critics Argued how did the plates move? Wegener could not prove it

21. Wilson to the Rescue! In the 1960’s Canadian Tuzo Wilson revisited Wegener’s work Volcanoes beneath the ocean erupted magma. Magma carried the plates further away from each other “Sea floor spreading” moved continents.

22. Sea Floor Speading

23. Landforms Read pp. 6-10

24. Compressional Forces Creating Fold Mountains Fold Mountains: Caused by compressional forces moving the earth’s crust together to collide Different forces and pressures create simple or complex forms

25. Fold Mountains

26. Differentiate Anti-cline and Syncline Anti-Cline: – It is the peak (top) of a folded mountain – An arch-like upfold – Top of the “A” Syncline: – It is the bottom or the valley – A downfold of rock layers – Bottom or the “S”

27. Fold Mountains:

28. What is Faulting? Faulting: – The breaking apart or fracturing of rock – Caused when rocks are compressed together under intense pressure – On earth’s surface or deep into the earth’s crust – Result of earth’s crust pushed up or dropped down – Plates move over, away, or past each other

29. Faulting

30. Tensional Forces creating Normal Fault Normal Fault: – Caused by tensional forces (crust moving away) – One plate drops down lower (hanging wall) than the upper plate (footwall).

31. Tensional Forces creating Rift Valley Rift Valley: – When two parts of the earth’s crust move away from each other – The plate in between drops down, leaving a valley

32. Compressional Forces creating Reverse Fault Reverse Fault: – There are compressional forces pushing one block up over the other – When the two pieces push against each other.

33. Compressional Forces creating Overthrust Fault Overthrust Fault: – Compressional forces (crust pushing together) – Crust has already undergone folding – Its folded layers are pushed up and thrust over layers on the fault’s other side

34. Volcanoes

35. What causes a Volcano to Erupt? 1. Heat is generated because of friction, pressure and decay of materials 2. Magma is produced when heat melts rock and materials beneath the crust

36. 3. Heat and pressure causes magma to rise. It reaches the surface through fractures, vents or craters 4. Lava is liquid rock. It is magma that reaches the earth’s surface

37. Volcanoes Remember! – The trigger for a volcano to erupt is heat. – Magma is produced when crusts meet. Magma is melted rock

38. Volcano Terms Ash: Small dust like fragments of rock, minerals and glass emitted from volcanoes Vent: Small opening where magma erupts Crater: Large opening where magma erupts Cinder: Low density igneous rock, characterized by bubbles, emitted from volcanoes. Larger than ash.

39. Volcanic Ash

40. Cinder

41. Volcanoes Three kinds: 1.Ash and Cinder Cones: – Shape is symmetrical – Steep sides – Large crater – Eruptions consist of mainly ash and cinder – Thick, slow flowing, rapidly solidifying lava. Creates violent eruptions

42. Ash and Cinder Cones

43. Shield Cone 2.Shield Cone: – Usually milder eruption – Little or no ash or cinders – Very thin, liquid lava – Broad, flat cones

44. Volcanoes 3. Composite Cones: – Undergoes periods of explosive and quiet activity – Ash and cinder mixed with lava – Weak spots may develop on sides with smaller lava flows forming smaller craters

45. Composite Volcanoes

46. Volcanoes –Related to Plates Meeting Usually found along plate boundaries

47. Plate Boundaries…and Volcanoes

48. Plate Boundaries…and Volcanoes. Why are Most Volcanos found where Plates Meet? – Because that’s where plates collide or converge – Denser plate melts at the subduction zone – Rocks melt to form magma – Pressure increases, magma rises and erupts – Volcanoes form

49. What about Volcanos found where Plates do Not Meet?

50. Intra-Plate Volcanoes

51. Why? – Plates move over magma hot spots in the lithosphere – Magma bursts through the crust – Forms linear chain of volcanic mountains – i.e. Hawaiian Islands

52. Global Patterns in the Location of Landforms What landform patterns can be seen from the diagram?

53. How did this Land Distribution Come About? Remember! – The earth’s landforms are constantly in a state of change – This is due to forces that build up the land and those that wear it down

54. In Conclusion First, we looked at forces that build up and shape landforms….next we will look at forces which wear down the land