1. German meteorologist Alfred Wegener proposed the hypothesis of continental drift
of continental drift says continents have moved slowly to their current
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 Antarctica, Africa, Australia, South America, and India -evidence of continental drift.
7. Glacial deposits, rock surfaces scratched and polished by glaciers have been found in South America, Africa, India, and Australia -evidence of continental drift.
8. Rock clues-same rocks are found on different continents. Mountains identical to parts of the Appalachian Mountains have been found in Greenland and Western Europe-evidence of continental drift.
9. WegenerÕs idea of
Continental Drift was rejected because
not explain how the continents could move.
10. using sound waves or SONAR, scientists discovered the mid-ocean ridge.
11. mid-ocean ridge is the worldÕs longest chain of mountains. Is where the sea-floor is spreading apart.
12. Harry Hess, a scientist, presented his theory of seafloor spreading to explain continental drift in the 1960's
13. seafloor spreading is caused by magma rising up towards the bottom of the ocean crust. Convection currents in the magma splits the crust apart along the mid-ocean ridge letting lava flow through the crack causing new seafloor.
14. youngest rocks are found near the mid-ocean ridge and rock gets older the farther away you get.
15. seafloor spreading causes the ocean to get wider! It pushes the continents away from each other.
16. theory of plate tectonics-EarthÕs crust and part of the upper mantle are broken into sections or plates.
17. plates-the sections of the lithosphere
18. lithosphere-the crunchy part of the Earth, is the crust and the very top of the mantle
19. asthenosphere-the gooey, plastic like, top part of the mantle that the lithosphere slides upon
20. plate boundaries-the edges of plates, where they meet.
21. convection currents in the mantle cause the movement of the plates.
22. convection current is the heating, rising, cooling, and sinking of magma. The rising and falling creates a current in the magma.
24. If one boundary changes, it causes changes at other boundaries.
25. divergent boundary-when two plates move AWAY from each other, § ˆ
26. divergent boundaries cause mid-ocean ridges and rift valleys!!
crust is created by divergent boundaries, mid-ocean ridges
28. If new crust is created, old crust must be recycled by the Earth.
29. convergent boundary-when two plates come together, ˆ §
30. convergent boundaries come together, denser oceanic plates/crust will sink beneath continental crust
31. subduction zone-where oceanic plates go down into the mantle.
32. volcanoes can form above subduction zones
33. deep-sea trenches are formed at convergent boundaries of two ocean plates.
34. subducted plates melt creating new magma. New magma can cause volcanoes or be used to form new mid-ocean ridges.
35. mountain ranges-when continental plates converge, they will crumple up.
36. transform boundaries-where two plates slide past each other.
37. Earthquakes occur at convergent boundaries and transform boundaries.
38. San Andreas Fault-a transform boundary in California that causes lots of earthquakes.
39. earthquakes produce three types of seismic waves, Primary, Secondary, and Surface waves
40. Primary waves move
41. Surface waves cause the most damage!!!
42. epicenter-surface location above the focus, where the earthquakes energy reaches the surface and spreads outward like a ripple of surface waves.
43. seismograph –instrument used to measure Seismic waves from earthquakes
44. magnitude is a measure of the energy released by an earthquake.
45. 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.
45. tsunami-ocean waves caused by earthquakes, can be as large as 30 meters tall.
46. volcano is an opening in Earth that erupts gases, ash, and lava
47. Volcanic mountains form when layers of lava, ash, and other material build up around these openings
48. Earth has more than 600 active volcanoes
49..volcanoes can be active, dormant (sleeping) or extinct (dead)
50. magma reaches EarthÕs surface and flows out through an opening called a vent
51. Ring of Fire is an area of frequent earthquakes and volcanic eruptions encircling the basin of the Pacific Ocean. It follows the plate boundaries.