In the space provided, write the letter of the definition that best matches the term or phrase.

Transcription

1 Skills Worksheet Directed Reading Section: The Changing Continents 1. What is the result of slow movements of tectonic plates? RESHAPING EARTH S CRUST In the space provided, write the letter of the definition that best matches the term or phrase. 2. shield a. rocks that have been exposed at Earth s surface b. large areas of stable rock older than 540 million years 3. rifting c. the process by which a continent breaks apart 4. cratons 5. Describe continental crust. 6. What probably causes continental lithosphere to become thinner and weaken? 7. What happens when the lithosphere weakens? 8. What are two ways by which continents can change? In the space provided, write the letter of the definition that best matches the term or phrase. 9. terrane 10. accretion 11. seamount 12. atoll a. a small volcanic island or underwater mountain b. the process by which a terrane becomes part of a continent c. a piece of lithosphere that has a unique geologic history d. a small coral island Holt Earth Science 19 Plate Tectonics

2 13. Describe the rocks and fossils of a terrane. 14. What is found at the boundaries of a terrane? 15. Describe the magnetic properties of a terrane. 16. What happens when a tectonic plate carrying a terrane subducts under a plate made of continental crust? 17. What two forms might terranes take when they become part of a continent? 18. Name three kinds of materials that can form terranes. 19. What often happens when large terranes and continents collide? 20. What is an example of a mountain chain that formed when a large terrane and a continent collided? EFFECTS OF CONTINENTAL CHANGE 21. Name three factors that affect a continent s climate. 22. How have movements of tectonic plates affected modern climates? 23. Most of Earth s continental surfaces were once covered by. Holt Earth Science 20 Plate Tectonics

3 24. Ice covered most of Earth when all the continents were located near. 25. What caused Earth s temperatures to change and its ice sheet to melt? 26. What happens to populations of organisms as continents rift or as mountains form? 27. What is an example of a unique species that evolved on Madagascar? 28. Why did unique species of plants and animals evolve on Madagascar? THE SUPERCONTINENT CYCLE 29. A picture of continental change throughout time has been constructed by a. paleontologists. b. geologists. c. geographers. d. scientists from many fields. 30. Supercontinents are a. large landmasses formed in the past from smaller continents. b. the large continents that exist today. c. pieces of large landmasses that broke apart. d. large oceans that covered Earth in the past. 31. According to the theory of the supercontinent cycle, what will probably occur in the future? a. No new supercontinents will form. b. Old supercontinents will reappear. c. Continents will stay as they are. d. A new supercontinent will form. 32. Supercontinents form when a. rifts form in the lithosphere. b. new convergent boundaries form after continents collide. c. heat builds up in Earth s interior. d. continental lithosphere subducts. Holt Earth Science 21 Plate Tectonics

4 33. What causes a supercontinent to break apart? a. Heat inside Earth causes rifts to form in the supercontinent. b. The convergent boundary between two continents becomes inactive. c. A new convergent boundary forms. d. The supercontinent cycle stops. 34. The supercontinent that formed about 300 million years ago is called a. Laurasia. b. Gondwanaland. c. Africa. d. Pangaea. 35. The body of water on the eastern edge of Pangaea was a. the Ural Sea. b. the Tethys Sea. c. the Panthalassa Ocean. d. the Russian Sea. 36. Pangaea was surrounded by a. mountains. b. seas. c. an ocean. d. other supercontinents. 37. One mountain range that formed when Pangaea was created was a. the Rocky Mountains. b. the Alps. c. the Himalayas. d. the Appalachians. 38. How were Laurasia and Gondwanaland created? a. Pangaea collided with another supercontinent. b. North America collided with Eurasia. c. Pangaea split from north to south. d. A rift split Pangaea from east to west. 39. The Tethys Sea eventually became a. the North Atlantic Ocean. b. Gondwanaland. c. the Mediterranean Sea. d. Laurasia. 40. How were South America and Africa formed? Holt Earth Science 22 Plate Tectonics

5 41. How was the South Atlantic Ocean formed? 42. How were India, Australia, and Antarctica formed? 43. How were the Himalaya Mountains formed? 44. When did the Himalaya Mountains begin to form? 45. How did the Rocky Mountains, the Andes, and the Alps form? 46. How did tectonic plate motion affect the oceans? 47. What will happen to Africa and the Mediterranean Sea in 150 million years if plate movements continue at current rates? 48. Describe how east Africa will change if plate movements continue at current rates. 49. What will cause the Atlantic Ocean to widen over the next 150 million years? Holt Earth Science 23 Plate Tectonics

6 50. What will happen to Australia if plate movements continue? 51. What will happen to the region west of the San Andreas Fault in 150 million years? 52. According to scientists predictions, what will happen to the continents in 250 million years? Holt Earth Science 24 Plate Tectonics

7 ANSWER KEY 9. in the same way that passengers are carried by a bus They don t always match the familiar outlines of continents and oceans. 12. by studying data from earthquakes 13. earthquake 14. that two or more plates may meet in the area 15. Some volcanoes form when plate motions generate magma that erupts on Earth s surface. 16. Pacific Ring of Fire 17. earthquakes 18. that the Pacific Ocean is surrounded by plate boundaries 19. C 20. F 21. A 22. D 23. B 24. E 25. in the middle of the ocean floor, around the edges of continents, and within continents 26. Magma rises to the surface as plates move apart. 27. warm and light 28. rift valley 29. on the ocean floor 30. the Red Sea, between the African and Arabian plates 31. subducts 32. deep-ocean trench 33. volcanic mountains 34. The colliding edges crumple and thicken, forming large mountain ranges. 35. the Himalalya Mountains 36. One plate subducts under the other, forming a deep-ocean trench. Fluids from the subducted plate cause mantle rock to melt and form magma. 37. a chain of volcanic islands called an island arc 38. Japan 39. As plates slide past each other horizontally, they scrape against each other. 40. They do not produce magma. 41. San Andreas Fault 42. North American and Pacific plates 43. fracture zones 44. the Chilean trench along the west coast of South America 45. the boundary of the North American and Eurasian plates 46. A 47. C 48. B 49. C 50. C 51. ridge push 52. It pushes the rest of the plate away from the mid-ocean ridge. 53. convergent boundaries 54. It rises to the surface. 55. slab pull 56. faster 57. drag on the bottoms of tectonic plates, ridge push, and slab pull SECTION: THE CHANGING CONTINENTS 1. They change the size and shape of the continents over millions of years. 2. A 3. C 4. B 5. It is thick with a high silica content. 6. heat from the mantle building up beneath the continent 7. A rift forms in the zone of weakness and the continent begins to break apart. 8. by breaking apart and by gaining material 9. C 10. B 11. A 12. D 13. They are different from those of neighboring terranes. 14. major faults 15. They generally do not match those of neighboring terranes. 16. The terrane is scraped off the subducting plate. 17. They might become mountains or simply add to the surface area of the continent. 18. seamounts, atolls, or large chunks of continental crust 19. Major mountain chains often form. 20. Himalaya Mountains 21. its location in relation to the equator and the poles, its location in relation Holt Earth Science 55 Plate Tectonics

8 ANSWER KEY to oceans and other continents, and its mountain ranges 22. When continents move, air flow and moisture change, causing climates to change. 23. ice 24. South Pole 25. Continents began to drift around the globe. 26. They may be separated and unique species may evolve from existing species. 27. the fossa 28. Madagascar separated from Africa about 165 million years ago and separated from India about 88 million years ago. This isolated the plants and animals on the island of Madagascar, leading to unique species evolving. 29. D 30. A 31. D 32. B 33. A 34. D 35. B 36. C 37. D 38. D 39. C 40. Gondwanaland broke into the two continents, one of which became South America and Africa. 41. A rift between South America and Africa opened about 150 million years ago. 42. The other continent of Gondwanaland separated to form them. 43. As India broke away from Australia and Antarctica, it moved north and collided with Eurasia. 44. about 60 million years ago 45. Collisions of the drifting continents welded new crust onto the continents and uplifted the land. 46. New oceans opened up and others closed. 47. Africa will collide with Eurasia. The Mediterranean Sea will close. 48. It will separate from the rest of Africa and move eastward, resulting in the formation of a new ocean. 49. The North American and South American plates will move westward and the Eurasian and African plates will move eastward. 50. It will move north and collide with Eurasia. 51. It will move to where Alaska is today. 52. They will come together to form a new supercontinent. Math Skills ,000,000: 3, 8, ,000,000: 1.6, 8, ,000,000: 6, 7, ,000,000 cm 8 10 to the 8th power km time in years time 611 km time 611 km km/yr 12,220,000 yrs Graphing Skills 1. oxygen and silicon; 74.3% 2. magnesium; 2.1% 3. Only small amounts of these elements are necessary to enrich a substance, because even the small amounts present in the continental crust are considered enriching. 4. Average Chemical Composition of Basaltic Layer of Oceanic Crust Oxygen 45.6% Silicon 23.0% Aluminum 9.0% Calcium 8.4% Iron 6.7% Sodium 2.0% Potassium 0.1% Other 5.2% Holt Earth Science 56 Plate Tectonics