Yale Undergraduate Science Olympiad 2017 Dynamic Planet Exam Questions 1. Do not begin the Exam until instructed to do so. 2. Fill out the information on the cover page of both the Exam Questions and Answer Sheet. 3. Answers that ask you to explain or describe, one or two sentences is enough. Full sentences are not necessary. 4. Write all answers (and work, if required) on the Answer Sheet. DO NOT WRITE on this Exam Questions packet. 1
Identify the following statements as either true (T) or false (F). 1. Continental crust tends to be older than oceanic crust. 2. Continental crust tends to be lower in silica than oceanic crust. 3. The total volume of continental crust is greater than the total volume of oceanic crust. 4. The asthenosphere consists of the mantle and lower crust. 5. The asthenosphere is composed primarily of magma. 6. Oceanic-oceanic convergent plate boundaries result in submarine orogenic belts. 7. P-waves are detectable at the point of the Earth opposite from an earthquake s epicenter. For questions 8 11, select the best answer from below. Answers may be used once or more than once. a. Observation of seismograms with two sets of P-waves and S-waves b. Seismic shadow zone c. Seismic tomography d. Wadati Benioff zone e. Seismic shadow zone 8. How was the boundary between the crust and mantle identified? 9. How was it determined that Earth has a liquid outer core? 10. What can be used to determine the angle of the down-going slab in a subduction zone? 11. How was the presence of the completely subducted Farallon Plate under North America determined? For questions 12 17, select the best geological system that occurs at the type of plate boundary listed. Answers may be used once or more than once. a. Orogenic belt b. Mid-ocean ridge c. (Subaerial) rift valley d. Subduction zone e. Strike-slip fault 12. Continental-continental convergent 13. Continental-continental divergent 14. Continental-continental transform 15. Continental-oceanic convergent 16. Oceanic-oceanic divergent 17. Oceanic-oceanic convergent 2
For questions 18 23, select the specific geological feature from the list below that is an example of the type of plate boundary listed. a. East Pacific Rise b. Himalaya c. Japan Trench d. Lake Baikal e. Mariana Trench f. San Andreas Fault 18. Continental-continental convergent 19. Continental-continental divergent 20. Continental-continental transform 21. Continental-oceanic convergent 22. Oceanic-oceanic divergent 23. Oceanic-oceanic convergent For questions 24 32, select all the best answers that apply from below. There may be more than one best answer. Answers may be used once or more than once. [10 points] a. Lithosphere b. Asthenosphere c. Continental crust d. Oceanic crust e. Mantle f. Outer core g. Inner core 24. Composed primarily of iron and nickel. 25. Composed primarily of ultramafic rocks. 26. Composed primarily of mafic rocks. 27. Composed primarily of intermediate to felsic rocks. 28. Layer with the highest temperatures. 29. Flows ductilely with convection cells. 30. Responsible for the Earth s magnetic field. 31. Comprises 84% of Earth s volume. 32. Divided into tectonic plates. 3
4 33. What type of sedimentary basin is shown in the diagram below? If you need to see the diagram in color, ask your proctor. a. Back-arc basin b. Foreland basin c. Intermontane basin d. Rift basin 34. What type of sedimentary basin is shown in the map below? The basin is in the region surrounded by the oval. a. Back-arc basin b. Foreland basin c. Intermontane basin d. Rift basin
35. Which specific geological feature is an example of an active constructive plate boundary? a. Mid-Atlantic Ridge b. Rocky Mountains c. Dead Sea Transform d. Aleutian Trench 36. Which specific geological feature is an example of an active destructive plate boundary? a. Mid-Atlantic Ridge b. Rocky Mountains c. Dead Sea Transform d. Aleutian Trench 37. Which specific geological feature is an example of an active conservative plate boundary? a. Mid-Atlantic Ridge b. Rocky Mountains c. Dead Sea Transform d. Aleutian Trench 38. Where do the largest earthquakes occur? a. Orogenic belts b. Mid-ocean ridges c. (Subaerial) rift valleys d. Subduction zones e. Strike-slip faults 39. Which rock types are typical of most oceanic crust? Select all that apply. [2 points] a. Basalt b. Diorite c. Gabbro d. Granite e. Limestone 40. Place the following events of the formation in order from oldest to youngest. [3 points] a. Alleghanian orogeny b. Collision of Avalonian continental fragments with Laurentia c. Collision of volcanic island arc with Laurentia d. Iapetus plate begins subducting under Laurentia e. Rifting of Pangaea 41. In question 40, what is the name of the orogeny in letter B? 42. In question 40, what is the name of the orogeny in letter C? 43. Which seismologist identified the boundary between the crust and mantle in 1909? 44. Which geologist developed radiometric dating of minerals and proposed mantle convection as a mechanism for continental drift? 45. Which Princeton University geologist originated the idea of seafloor spreading? 46. What is the term for an inclusion in igneous rock that provides evidence for mantle composition? 47. What type of melting occurs at mid-ocean ridges due to a decrease in overlying pressure? 48. What type of melting occurs in subduction zones due to addition of volatiles such as water? 5
6 49. List two notable examples of hotspots in the United States. [2 points] 50. What is the term for proposed hotspot mechanisms that originate from relatively fixed areas at the core-mantle boundary? 51. What type of sedimentary basin occurs due to lithospheric flexure adjacent to orogens? 52. What is the term for the region between a volcanic arc and an oceanic trench? 53. What is the term for the area of marine sediment that accumulates on the non-subducting plate at a convergent plate boundary? 54. What is the process by which magmas residing underground progressively remove and segregate minerals as it cools? 55. In the above process, does the resulting magma become more felsic or mafic? 56. What phenomenon often occurs on reclaimed land during earthquakes and results in soil loosing stiffness and acting like quicksand? 57. What device is mounted in skyscrapers such as Taipei 101 and the Tokyo Skytree in order to reduce the amplitude of vibrations from earthquakes or wind? Questions 58 60 concern the graph below. 58. What type of strength increases linearly with confining pressure? 59. What type of strength decreases exponentially with temperature? 60. What is name of the shaded zone (around 15 km deep), the strongest part of Earth s crust?
7 61. Who most prominently originated the theory of continental drift? List three pieces of evidence he or she used to support the theory. [4 points] 62. Explain briefly ridge push, slab pull, and trench suction. Additionally, put a star or other visible marking in your answer next to the force that is strongest. You may draw diagrams to aid your answer. [6 points] 63. Explain briefly the impact of plate tectonic activities on causing major ice ages. [2 points] 64. List the lettered events in the cross section below from oldest to youngest. [6 points] Answer the following questions about the cross section above. 65. Assuming that layer T was deposited 10 ka, in what type of environment is the cross section most likely to be found today? a. Somewhere like Connecticut with cold winters b. Shallow reef c. Deep ocean d. Rainforest 66. What does the sequence of layers D, E, and N indicate about the changes in depositional environment over time? a. Marine regression b. Marine transgression c. Evaporating sea d. Periodic volcanic eruptions 67. Are the presence of faults S and Z more indicative of compressional or extensional stress?
8 Questions 68 69 use the (not entirely accurate) data below. Assume a simple situation in which plates float on the asthenosphere like blocks of wood in water (see diagram below for reference). Your answers will require calculations from the data. Show your work. Label units. You do not need to use significant figures. Average Density of Continental Lithosphere 2.7 g/cm 3 Average Density of Oceanic Lithosphere 2.9 g/cm 3 Average Density of Mantle 3.3 g/cm 3 Average Thickness of Continental Lithosphere Average Thickness of Oceanic Lithosphere 200 km 100 km 68. What thickness of oceanic lithosphere is submerged in the asthenosphere, to the nearest kilometer? [3 points] 69. How much does the elevation of the top of the continental lithosphere decrease if 2 kilometers of sediment is eroded away, to the 100 meters? [7 points] 70. The locations of modern-day cities Halifax (in Canada) and Casablanca (in Morocco) were roughly adjacent 220 Ma. Given that the distance between the two cities is roughly 4900 km now, what is the average rate of widening of the Atlantic Ocean over the past 220 Ma in cm/year? What is the average speed of motion of the North American plate over the same period of time in cm/year? Show your work. Label units. Use significant figures. [4 points]
YUSO 2017 DYNAMIC PLANET Image for Question 33 Image for Questions 68 69
Yale Undergraduate Science Olympiad 2017 Dynamic Planet Answer Key 1. Mark questions that are incorrect. You do not need to write the correct answer in. 2. 3. Underlined portions are the essential parts to earn credit for questions with one phrase answers. 4. If there are any questions regarding how to grade an answer, refer to the Exam Questions. If that fails, contact Kento Tanaka, (808) 554-9183, kento.tanaka@yale.edu. I will be around all day and I will also check my phone frequently. Score: 100/100 1. T 2. F 3. T 4. F 5. F 6. F 7. T 8. A 9. B 10. D 11. C 12. A 13. C 14. E 15. D 16. B 17. D 18. B 19. D 20. F 1
21. C 22. A 23. E 24. F, G (2 points) 25. E (also accept B as long as they have E) 26. D 27. C 28. G 29. B 30. F 31. E 32. A (also accept C and/or D as long as they have A) 33. D 34. A 35. A 36. D 37. C 38. D 39. A, C (2 points- 1 point for each correct answer; subtract 0.5 points for each incorrect answer) 40. oldest D, C, B, A, E youngest (3 points for entirely correct, 2 points for 1 letter misplaced or 2 letters switched, 1 point for a couple of letters in the general correct place, 0 points for completely wrong or blank) 41. Acadian orogeny 42. Taconic orogeny 43. Andrija ć 44. Arthur Holmes 45. Harry Hess 46. Xenolith 47. Decompression melting 48. Flux melting 49. Hawaii, Yellowstone (any order) (2 points) 50. Mantle plumes 51. Foreland basin 52. Forearc 53. Accretionary wedge or accretionary prism 54. Fractional crystallization 55. Felsic 56. Soil liquefaction 57. Tuned mass damper or harmonic absorber 58. Brittle strength 59. Ductile strength 60. Brittle-ductile transition zone 2
61. Alfred Wegener (1 point); any three of the following (3 points): Shape of continents fit like jigsaw puzzle Correlation of fossils (same types of fossils found across multiple continents) Types of fossils did not match modern climates (e.g. tropical plants in cold climates) Glacial deposits (evidence of glacial activity in modern low-latitude tropical areas) Correlation of mountain ranges across both sides of the Atlantic 62. (6 points, Tiebreaker 1) Award points if drawings convey the same information. Detailed answers below, full credit as long as they get the general idea correct and word it precisely/accurately. Ridge push: Lithosphere slopes away from ridge because it is newer, thinner, warmer, and less dense. (or ridge is higher than surrounding plate/lithosphere), because it is higher, the force of gravity pushes down on the surrounding older, colder, denser areas. (2 points) Slab pull: Subducted portions of the plate are colder and denser than the underlying mantle; once they are subducted, their weight helps pull the rest of the plate along. (2 points) (Slab pull should be labelled with a star or other visible marking, 1 point) Trench suction: Subducted plate drives convective flow in surrounding mantle, which pulls the plate even more. (1 point) 63. The changing positions of continents can interrupt ocean currents that distribute heat from low to high latitudes. (2 points, Tiebreaker 3: 1 point for something about continent positions and 1 point for ocean currents distributing heat) 64. oldest D, E, N, X, S, G, M, F, Z, B, T youngest (6 points) 65. A 66. B 67. Extensional 3
68. ( ) (100 km) = 88 km (1 point for equation, 1 point for answer, 1 point for units) 69. (7 points, Tiebreaker 2) g 2.7 cm Pre-erosion height: 200 km ( 3 3.3 g ) (200 km) = 36. 36 km (2 points; intermediate cm 3 answer not required) g 2.7 cm Post-erosion height: 198 km ( 3 3.3 g ) (198 km) = 36 km (2 points; intermediate cm 3 answer not required) 36. 36 36 km = 0.4 km or 400 m (1 point for subtracting, 1 point for correct answer, 1 point for proper rounding and unit labelling) 70. (4 points) Order of answers matters ( 4900 km 220 Ma ) (100,000 cm km ) ( answer, 1 point for units) 2.2 cm year = 1.1 cm (1 point) 2 year Ma 1,000,000 year ) = 2.2 cm year (1 point for equation, 1 point for 4