Chapter 9 and 10

1. Chapter 9 and 10 The interior of the earth and it’s surface

2. The Interior of the Earth • We can’t go there • Use the shock waves an earthquake makes to investigate it. • Called seismic waves • Two types • S waves (sheer waves) • P waves (pressure waves) • Measured with a seismograph

3. Seismograph Heavy object Drum

4. Seismograph As ground shakes the base moves but the weight stays still

7. Seismic waves • Penetrate earth and return to surface. • Speed and direction change • S waves can’t go through liquids • P waves can, but they slow down. • As the waves go through the earth at 2900 km down, the S waves stop and the P waves slow down • At 5105 Km down the P waves speed up • What does this tell us?

8. The Earth’s Core • The center of the earth • Two layers • Inner core • Iron and Nickel • 5000º C • Pressure keeps it solid • Responsible for magnetic field?

9. The Earth’s Core • The outer core • Iron and Nickel • 2200º C to 5000º C • Not as much pressure so it is liquid • How do they know • P waves are pressure waves • Will go through liquid • S waves are sheer waves • won’t go through liquids

10. S waves Liquid

11. P waves

12. Total Shadow No waves

14. The Mantle • Above the outer core • 80% of the earth’s volume • 68% of the earth’s volume • Studied rocks from volcanoes • Have studied rocks from the ocean floor • Silicon, oxygen, iron, magnesium • Density increases with depth • Because there’s more iron • Measured by speed of the seismic waves

15. The Mantle • Temperature increases with depth • Has plasticity • What is plasticity? • A solid that can flow like a liquid • Silly putty • 870º C -2200º C

16. The Moho • the thin boundary layer between the mantle and the crust • 32-64 km • Discovered by Andrija Mohorvičić • Found seismic waves changed speed at this level • Either different composition or density.

17. The crust • Thin outer layer we live on • If the earth were the size of an apple, the crust would be thinner than the peel • 8-32 km • Two kinds • Oceanic • Less than 10 km • all basalt- dense

18. The crust • Continental crust • Thicker- averages 32 km, up to 70 km • Top layer granite- less dense, on top of dense basalt • Earth’s crust also called lithosphere • Lithosphere broken into large plates (called tectonic plates)

19. 0 km Crust 32 km Moho Mantle 2900 km Outer Core 5150 km Inner Core 6500km

20. Continent Ocean Granite Basalt Mantle

21. Chapter 10 How the crust moves

22. Crust • Continental – • Thicker • Granite and basalt • Oceanic • Thinner • All Basalt • Stress- the pushes and pulls on the crust • causes changes in the rock • Shape • Volume • Compresses or expands • Deformation- breaking, tilting, and folding of of rocks

23. Stress • Three types • Compression- pushed together

24. Stress • Three types • Compression- pushed together • Moves land higher up and deeper

25. Stress • Tension • Pulled apart • Stretches like taffy • Thinner in the middle

26. Stress • Tension • Pulled apart • Stretches like taffy • Thinner in the middle

27. Stress • Shearing- pushes in two opposite horizontal directions • Rocks are torn apart or bent

28. Stress • Shearing- pushes in two opposite horizontal directions • Rocks are torn apart or bent

29. Stress changes • Shape • Volume • Density • Can cause cracks - fracture • Fracture along smooth surface is called a joint • Joints are parallel

30. Faults • A break or crack where rocks move • Where earthquakes happen • Hanging wall- above the fault • Foot wall- below the fault • Three types of fault • tension causes normal fault • Compression causes reverse fault and thrust fault

31. Normal fault • Tension pulls apart • Hanging wall moves down Hanging wall Foot wall

32. Normal fault • Tension pulls apart • Hanging wall moves down

33. Reverse fault • Compression pushes together • the hanging wall up Hanging wall Foot wall

34. Reverse fault • Compression pushes together • the hanging wall up

35. Thrust Fault • Compression continues • The hanging wall is pushed over the foot wall • end up with layers of rock repeated • Older rock on top of younger rock

36. Thrust fault Youngest Rock Oldest Rock

37. Lateral Fault • Caused by shear stress • Blocks move sideways

38. Lateral Fault • Caused by shear stress • Blocks move sideways

39. Faulted Mountains and Valleys • A series of normal faults will cause mountains to be uplifted. • Called Fault-block mountains • Sierras • Valleys will also be formed • Called rift valleys • Death Valley

40. Fault Block Mountain

41. Fault Block Mountain

42. Rift valleys

43. Rift valleys

44. Folding • Some times rock doesn’t break • It forms folds- like wrinkles • Upward fold- anticline • Downward fold- syncline • Vary in size, from microscopic to mountain forming

45. Anticline Syncline

46. Why Fold • Why don’t they break • Temperature- hot rock is easier to bend • Pressure- higher pressure more likely to fold • Type of rock- some are more brittle, some are more malleable • Gradual force bends, sudden force breaks

47. Plateau • Flat area made of layers of flat-topped rocks high above sea level • Can be formed like fault block mountains • Or by lava flows (lava plateau) • Colorado plateau- West of the Rocky mountains • formed Grand canyon • Rivers cut large plateau into several smaller ones

48. Domes • Magma forms a bubble underneath the crust, without erupting • Half sphere surrounded by flat land • If worn into separate peaks they are called dome mountains

49. The Crust Floats • On the mantle • Because it is less dense • The floating crust pushes down • The crust pushes up. • Balance of forces called isostasy • More material floats lower

50. Isostasy Crust Mantle