Dynamic Earth

1. Dynamic Earth This unit will cover: layers of the earth, plate tectonics, volcanoes, earthquakes

2. 1. Crust: • Continental crust • Oceanic crust 2. Mantle • Largest section • Includes the asthenosphere toward the top • Solid part and semi-liquid parts to it 3. Core • Inner core (Solid—Iron) • Outer Core (Liquid) Earth’s Internal Structure: Compositional Layers

3. Internal Structure of Earth Upper Mantle Crust Lower Mantle Outer Core Inner Core “Asthenosphere”

6. The Lithosphere contains the crust and the solid mantle

7. Early observations of the world • Alfred Wegener proposed an idea for CONTINENTAL DRIFT. • Continental Drift= proposed that the world’s continents were stuck together • He called his super continent PANGEA.

8. Pangea Alfred Wegener

9. Rejected….. • Alfred Wegener idea of Pangea was rejected after his death in 1930. • The use of Seafloor spreading was a new idea that was promoted.

10. Technology used in Seafloor Spreading • Sonar—uses sound waves to measure the depth of the bottom of the ocean • Magnetometer—is a device to measure the changes in magnetic fields. Antarctic- using magnetometer Sonar

11. Results… • Map Generated Topographical Maps that showed the deep sea trenches and ocean ridges. Picture of California’s Coast Blue—water Green, brown--land

12. Theory of Plate Tectonics • Which states that the Earth’s crust and rigid upper mantle is broken into plates • The plates move in different directions and different rates over time.

13. Different Plates Around the World Ring of Fire

14. Plate Boundaries • Divergent Boundaries • Places where plates are coming apart • Convergent Boundaries • Places where plates crash or crunch together • Transform Boundaries • Places where plates slide past each other

15. Divergent Boundary • Places where plates are coming apart

16. Convergent Boundary With Subduction Plate Plates crash into each other

17. Transform Boundary • Places where plates slide past each other

18. San Andres Fault, California

19. PlateMotions • Assume plates are rigid (no internal deformation: bending or flexing) • Obtain plate motion: • Directions • Rates of movement

20. Convection Cell— that regulates the flow of magma. There are also convection cells in the atmosphere for our weather.

21. What do plate tectonics form? • Earthquakes • Hotspots • Volcanoes

22. Earthquakes

23. Earthquakes Most destructive forces on Earth. But it is buildings and other human structures that cause injury and death, not the earthquake itself 1988 - Soviet Armenia: magnitude 6.9, 25,000 people died 1985 - Mexico City: magnitude 8.1, 9500 people 1989 - Loma Prieta, CA: magnitude7.1,40 peopledied 1995 - Kobe, Japan: magnitude 7, ~6000 people died

24. Where do earthquakes occur? • They occur when plates are diverging, sliding past each other, colliding or going underneath each other. • There are three types of faults • Strike-Slip Fault • Normal Fault • Reverse Fault • Thrust Fault

25. 3 types of faults

26. Strike Slip Fault • Occurs horizontally when two plates slide past each other • San Andres Fault in California • Causes Rail roads to bend

27. Normal Fault • Occur vertically and when the plates are diverging • Happen where the lithosphere is being pulled apart

28. Reverse Fault • Occurs vertical, the plates collide together pushing the rock upward • Example—thrust • In the ocean causes tsunami

29. PARTS OF EARTHQUAKES • HYPOCENTER—LOCATIONS OF EARTHQUAKE UNDERNEATH THE GROUND. • EPICENTER—LOCATION OF EARTHQUAKE ON THE SURFACE

30. epicenter hypocenter Transform fault

31. P and S Wave

32. Body Waves P waves: • Pressure or compressional waves. Vibrate parallel to direction of wave travel like a slinky. • Fast travel: 4-7 km/sec (15,000 mph) • P is primary, or first wave to arrive at recording station S waves: • Shear waves. Vibrates perpendicular to direction of wave travel. Like snapping a rope • Slower than P wave: 2-5 km/sec (11,000 mph) • So S is secondary, or second wave to arrive at recording station

35. Locating the Epicenter of an Earthquake • P, S and surface waves all start out at same time. • The further you are away from the quake, the longer the time span between arrival of P and S wave. • The distance of the seismometer to the earthquake can be determined by the time between the arrival of P wave and arrival of S waves. • Can tell the distance, but not the direction. • Therefore, multiple sites must be used to find epicenter.

39. Kodiak, AL 1964 Tsunami Damage

40. Richter Scale • Measures the magnitude of an earthquake from 1-10

41. RICHTER SCALE MEASURES MAGNITUDE FROM 0-10

42. Hotspots

43. Hot Spots • Islands associated with hot spots (island chains, mid-ocean ridges, triple junctions). • Iceland (mid-ocean ridge). • Galapagos Islands (triple junction). • Island of Hawaii (mid-plate volcanic chain; hot spot trace). • Linear island chains form as plate moves over hot spot. • Hawaiian islands get older in direction of plate movement (older away from mid-ocean ridge).

45. VOLCANOES http://georoc.mpch-mainz.gwdg.de/volcano.gif

47. Volcanoes • Basic parts of a volcano • Crater (depression at the summit of a volcano, connected by a vent or pipe to the magma chamber below) • Caldera (crater more than 1 km in diameter, formed at the summit of a volcano when lava is drained from an underground magma chamber, causing the summit of the volcano to be unsupported, and to collapse)

48. Example of Caldera • Crater Lake in Oregon. This volcano was so violent that the top of the mountain was blown off. Now all is left is a beautiful lake.

49. Pit crater (collapse features on the flanks or summit of a volcano that are smaller than the main caldera at the summit of a volcano) • Vent (pipe-like conduit from the magma chamber to the surface) • Fumaroles (secondary vents on the flank of a volcano which emit steam and other gases)

50. http://volcano.und.nodak.edu/vwdocs/vw_hyperexchange/parts.htmlhttp://volcano.und.nodak.edu/vwdocs/vw_hyperexchange/parts.html