1. German meteorologist Alfred Wegener proposed the hypothesis of continental drift
2. According to the hypothesis of continental drift, continents have moved slowly to their current locations
3. Wegener suggested that about 200 million years ago, all continents once were connected as one landmass called Pangaea
4. Pangaea means “all land”
5. Wegener’s ideas about continental drift were controversial and not believed until after 1930.
6. Fossil clues, climate clues, and rock clues provided evidence that continental drift occurred.
7. Fossils of Mesosaurus, a freshwater dinosaur provided evidence that continental drift occurred.
8. Tropical plant fossils, Glossopteris, have been found in Antarctica, Africa, Australia, South America, and India.
9. Glacial deposits, rock surfaces scoured and polished by glaciers have been found in South America, Africa, India, and Australia.
10. Rock clues-similar rock structures are found on different continents. Mountains identical to parts of the Appalachian Mountains have been found in Greenland and Western Europe.
11. Wegener’s idea of Continental Drift were rejected because scientists could not give any explanations how the continents could move.
12. In the 1940’s and 1950’s, scientists began using sound waves to map the ocean floor.
13. Sound waves echo off the ocean floor & the longer they take to return to the ship, the deeper the ocean.
14. using sound waves, scientists discovered an underwater mountain chain called the mid-ocean ridge.
15. mid-ocean ridge is the world’s longest chain of mountains. Is where the sea-floor is spreading apart.
16. Harry Hess, a scientist, presented his theory of seafloor spreading to explain continental drift in the 1960,s
17. 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
18. 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.
19. youngest rocks are found near the mid-ocean ridge and rock gets older the farther away you get.
20. seafloor spreading causes the ocean to get wider! It pushes the continents away from each other.
21. 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.
Directions: Study the following diagram of the seafloor. Then match the letters to the statements below.
Directed Reading for Mastery
______A. Molten rock flows onto the seafloor and hardens as it cools.
_______B. Hot, molten rock is forced upward toward the seafloor at a mid-ocean ridge.
_______C. New seafloor moves away from the ridge, cools, becomes denser, and sinks.
_______D. Molten rock pushes sideways in both directions as it rises, moving the
mantle with it.
22. theory of plate tectonics-Earth’s crust and part of the upper mantle are broken into sections.
23. plates-the sections of the lithosphere
24. lithosphere-the crunchy part of the Earth, is the crust and the very top of the mantle
25. asthenosphere-the gooey, plasticlike, top part of the mantle that the lithosphere slides upon
26. plate boundaries-the edges of plates, where they meet.
27. convection currents inside the Earth are believed to cause the movement of the plates.
28. convection current is the heating, rising, cooling, and sinking of magma. As magma gets heated it becomes less dense which causes it to rise upward through the mantle. As it cools, it sinks back downward. The rising and falling creates a current in the magma.
29. three movements of plates-towards each other, away from each other, and past each other like cars on a highway
30. If one boundary changes, it will cause changes at other boundaries.
31. divergent boundary-when two plates move AWAY from each other, ß à.
32. divergent boundaries cause mid-ocean ridges!!
33. new crust is created by divergent boundaries, mid-ocean ridges
34. If new crust is created, old crust must be recycled by the Earth.
35. convergent boundary-when two plates come together, àß.
36. convergent boundaries come together, denser oceanic plates/crust will sink beneath continental crust
37. subduction zone-where oceanic plates goes down into the mantle.
38. volcanoes can form above subduction zones
39. deep-sea trenches are formed at convergent boundaries of two ocean plates.
40. subducted plates melt creating new magma. New magma can cause volcanoes or be used to form new mid-ocean ridges.
41. mountain ranges-when continental plates converge, they will crumple up.
42. transform boundaries-where two plates slide past each other.
43. Earthquakes occur at convergent boundaries and transform boundaries.
44. San Andreas Fault-a transform boundary in California that causes lots of earthquakes.
45. seismic waves- energy release as rocks move and break in the crust during an earthquake
46. fault-area where rocks break and move because of plate movement
47. faults can cause breaks and shifts in rock layers.
Earthquakes and Volcanoes!
48. focus-the exact point where the energy is released during an earthquake, seismic waves travel outward from the focus.
49. earthquakes produce three types of seismic waves, Primary, Secondary, and Surface waves
50. Primary waves move the fastest
51. Surface waves cause the most damage!!!
52. epicenter-surface location above the focus, where the earthquakes energy reaches the surface and spreads outward like a ripple of surface waves.
53. seismograph –instrument used to measure Seismic waves from earthquakes
54. seismologists -Scientists who study earthquakes and seismic waves
55. magnitude is a measure of the energy released by an earthquake.
56. 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.
57. tsunami-ocean waves caused by earthquakes, can be as large as 30 meters tall.
58. volcano is an opening in Earth that erupts gases, ash, and lava
59. Volcanic mountains form when layers of lava, ash, and other material build up around these openings
60. Earth has more than 600 active volcanoes
61..volcanoes can be active, dormant (sleeping) or extinct (dead)
62. magma reaches Earth’s surface and flows out through an opening called a vent
63. crater the steep walled depression around a vent.
64. Ring of Fire is an area of frequent earthquakes and volcanic eruptions encircling the basin of the Pacific Ocean. It follows the plate boundaries.
65. fault-block mountains are formed by huge faults
66. Rift valleys and mid-ocean ridges are cause by divergent plates.
67. The Indian plate and Asian plate boundary is a convergent boundary. It is moving at 5 cm per year causing the Himalayan Mountains to keep growing.
68. strike-slip faults are found along divergent boundaries moving in opposite directions.
69. scientists can measure the movement of plates using satellites and lasers.
70. Hawaii is moving towards Japan at 8.3 cm per year.
71. three types of plate boundaries are convergent, divergent, and transform.