1. German meteorologist Alfred Wegener proposed the hypothesis of continental drift
2. hypothesis of continental drift says continents have moved slowly to their current locations
3. Wegener said about 200 million years ago, all continents were connected as one landmass called Pangaea
4. Fossil clues, climate clues, and rock clues provided evidence that continental drift occurred.
5. Fossils of Mesosaurus, a freshwater dinosaur - evidence of continental drift.
6. Tropical plant fossils,
Glossopteris, have been found in
7. Glacial deposits, rock
surfaces scratched and polished by glaciers have been found in
8. Rock clues-same rocks are found on different continents.
Mountains identical to parts of the
9. Wegener’s idea of Continental Drift was rejected because scientists could not explain how the continents could move.
10. In the 1940’s and 1950’s, scientists began using SONAR or sound waves to map the ocean floor.
11. Sound waves echo off the ocean floor & the longer they take to return to the ship, the deeper the ocean.
12. using sound waves, scientists discovered the mid-ocean ridge.
13. mid-ocean ridge is the world’s longest chain of mountains. Is where the sea-floor is spreading apart.
14. Harry Hess, a scientist, presented his theory of seafloor spreading to explain continental drift in the 1960's
15. seafloor spreading is caused by magma rising up towards the bottom of the ocean crust. Convection currents in the magma split the crust apart along the mid-ocean ridge letting lava flow through the crack causing new seafloor.
16. Glomar Challenger-1968, research ship that discovered that rocks closest to mid-ocean ridge were the youngest and that the farther away, the older the rocks.
17. youngest rocks are found near the mid-ocean ridge and rock gets older the farther away you get.
18. seafloor spreading causes the ocean to get wider! It pushes the continents away from each other.
19. magnetic alignment in rocks on the seafloor, on both sides of the mid-ocean ridge, has recorded the periodic reversals of the Earth’s magnetic field.
20. theory of plate tectonics-Earth’s crust and part of the upper mantle are broken into sections.
21. plates-the sections of the lithosphere
22. lithosphere-the crunchy part of the Earth, is the crust and the very top of the mantle
23. asthenosphere-the gooey, plasticlike, top part of the mantle that the lithosphere slides upon
24. plate boundaries-the edges of plates, where they meet.
25. convection currents in the mantle cause the movement of the plates.
26. convection current is the heating, rising, cooling, and sinking of magma. hot magma is less dense which causes it to rise upward through the mantle, as it cools, it sinks back down. The rising and falling creates a current in the magma.
27. three movements of plates-towards each other, away from each other, and past each other like cars on a highway
28. If one boundary changes, it will cause changes at other boundaries.
29. divergent boundary-when two plates move AWAY from each other, ß à.
30. divergent boundaries cause mid-ocean ridges!!
31. new crust is created by divergent boundaries, mid-ocean ridges
32. If new crust is created, old crust must be recycled by the Earth.
33. convergent boundary-when two plates come together, àß.
34. convergent boundaries come together, denser oceanic plates/crust will sink beneath continental crust
35. subduction zone-where oceanic plates go down into the mantle.
36. volcanoes can form above subduction zones
37. deep-sea trenches are formed at convergent boundaries of two ocean plates.
38. subducted plates melt creating new magma. New magma can cause volcanoes or be used to form new mid-ocean ridges.
39. mountain ranges-when continental plates converge, they will crumple up.
40. transform boundaries-where two plates slide past each other.
41. Earthquakes occur at convergent boundaries and transform boundaries.
43. seismic waves- energy release as rocks move and break in the crust during an earthquake
44. fault-area where rocks break and move because of plate movement
45. faults can cause breaks and shifts in rock layers.
46. focus-the exact point where the energy is released during an earthquake, seismic waves travel outward from the focus.
47. earthquakes produce three types of seismic waves, Primary, Secondary, and Surface waves
48. Primary waves move the fastest
49. Surface waves cause the most damage!!!
50. epicenter-surface location above the focus, where the earthquakes energy reaches the surface and spreads outward like a ripple of surface waves.
51. seismograph –instrument used to measure Seismic waves from earthquakes
52. seismologists -Scientists who study earthquakes and seismic waves
53. magnitude is a measure of the energy released by an earthquake.
54. Richter magnitude scale is used to describe the strength of an earthquake Each magnitude is 10 times stronger than the last. Magnitude 2 is 10 times stronger than a magnitude 1 and a magnitude 3 is 100 times stronger than a 1.
56. volcano is an opening in Earth that erupts gases, ash, and lava
57. Volcanic mountains form when layers of lava, ash, and other material build up around these openings
58. Earth has more than 600 active volcanoes
59..volcanoes can be active, dormant (sleeping) or extinct (dead)
60. magma reaches Earth’s surface and flows out through an opening called a vent
61. crater the steep walled depression around a vent.
62. Ring of Fire is an area of frequent earthquakes
and volcanic eruptions encircling the basin of the
63. fault-block mountains are formed by huge faults
64. Rift valleys and mid-ocean ridges are cause by divergent plates.
65. The Indian plate and Asian plate boundary is a convergent
boundary, is causing the
66. strike-slip faults are found along divergent boundaries moving in opposite directions.
67. scientists can measure the movement of plates using satellites and lasers.
69. three types of plate boundaries are convergent, divergent, and transform.