Chapter 7 Plate Tectonics Answers to Review Questions 1. a) Similarity of coastlines (more precisely the similarity of the edge of the continental shelves). Especially South America and Africa. b) Similarities of the edges of the continental shelves, similar rock types on each side of oceans match, Fossils match across the seas, ancient climates are consistent (glaciers in southern Africa, South America, India and Australia, tropical climate in Eastern U. S. Europe and Siberia produced major coal fields). The fresh water Mesosaurus aren't found globally thereby indicating that they weren't very mobile, but they are found on adjacent areas of the reassembled South America and Africa. c) No mechnisms, that seemed logical with the current understanding, were proposed to allow the continental plates to move. Wegener suggested that continents break through the ocean floor when they moved and that tidal forces were responsible for this movement. d) Wegener continued to test his hypothesis by looking for new testable evidence. He died in Greenland trying to determine how much Greenland had moved during the last 200 million years. 2. a) A) ocean floor subducting under a continent B) ocean subducting under an ocean floor. C) continent subducting under a continent. 2. b) Ocean floor 2 c) Because they do not contain large amount of water and they do not subduct as deep. The water serves as a eutectic which lowers the melting point of rock. Further more the water relases large amount of gas. 2. d) They are similar in that they both can product volcanoes. They are different in that in one case the volcanoes are on a continent and the other the volcanoes form islands. 3. The Baja peninsula and the area of Los Angeles is sliding northward and is not beng subducted. 4. a) 3 b) toward. The arrows on the subduction zone. c) subduction is causing melting and the melted magma is rsing to the surface forming volcanoes. d) No subduction underneath and no rifting apart. If rifting started you could have some volcanoes. 5. Olympus Mons on Mars is the largest volcano tht has been identified in the solar system. This doesn't tell us anything about the interior of Mars because we don't have detailed seimological information about the interior of Mars. On the surface of Mars there is one region with alternating magnetic strips which indicates that one area of Mars may have had something like plate tectonics, but it isn't widespread. 6. The first one with uniform magnetic stripes has magma coming up at a constant velocity. The magma coming up in the 2nd one is slowing down, thus making the magnetic stripes wider near the crest. 7. Antarctica, Australia and New Zealand were separated from the other plates by 90 million years ago and have remained separated until today. North America on the other hand has been in touch with Asia and South America more recently, so that causes huge differences in the evolution of the animals. 8. Eurasia 9. Light magma rises to form hot spots and volcanoes. Heavy plates sink. When two continents collide with nearly the same density, huge mountains are produced. 10. a) London and Boston, London and Denver, London and Mexico City b) Darwin and Beijing, Delhi and Beijing, Honolulu and Beijing, Darwin and Honolulu. c) Boston and Denver, Denver and Mexico City, Boston and mexico City.