EAS-1430 Introduction to the Solid Earth Exam 1 PDF

## EAS-1430 Introduction to the Solid Earth ### EXAM 1 ### 20 September 2024 #### READ: Write your name on the answer sheet (last page). You may tear off the answer sheet from this questionnaire but submit both at the end of the exam. Note that there is a part B after the multiple-choice section. G...

## EAS-1430 Introduction to the Solid Earth ### EXAM 1 ### 20 September 2024 #### READ: Write your name on the answer sheet (last page). You may tear off the answer sheet from this questionnaire but submit both at the end of the exam. Note that there is a part B after the multiple-choice section. Good luck! **A. Select the best answer and place an X on the letter of your choice on the answer sheet. If you need to change your choice, put a horizontal line across the mistaken choice and place an X on the new choice.** 1. Which of the following is the correct order of steps in the scientific method? * (a) initial observation, hypothesis, prediction, accept or reject hypothesis, test the prediction * (b) initial observation, question, hypothesis, prediction, test the prediction, accept or reject hypothesis * (c) question, initial observation, test the prediction, prediction, accept or reject hypothesis * (d) prediction, test the prediction, hypothesis, question, accept or reject hypothesis * (e) initial observation, prediction, test the prediction, question, accept or reject hypothesis 2. Why is explaining some natural event as an “act of God” not scientific? * (a) one cannot observe the natural event, * (b) it doesn't make a testable prediction, * (c) it is not an explanation for the event * (d) it is not possible to formulate a question based on the observation of the natural event, * (e) none of the above 3. The “K-T boundary" refers to what? * (a) The time when humans appeared on Earth, * (b) any clay layer enclosed in limestone * (c) the time when the Cretaceous period ended and the Tertiary period began, * (d) the time when dinosaurs appeared on Earth, * (e) the time when the first animals with hard parts appeared on Earth, 4. Why did the Alvarezes study K-T boundary clay layers at other sites (Denmark and New Zealand) besides the first site (Italy) that they studied? Because... * (a) the other authors of the paper were from those other countries * (b) two other meteorites hit Earth besides the one that hit Italy * (c) if they claimed the effects of the meteorite impact were global, they needed sample locations that were more global * (d) they could not return to the Italian site * (e) those were the only other sites that preserved the K-T clay layer 5. Before the discovery of the high Iridium (Ir) layer at the K-T boundary, the Ir that they were going to measure in the sedimentary rocks (limestone) was thought to come primarily from * (a) decay of other elements in the sediment * (b) solar radiation, * (c) formed in the sediment, * (d) cosmic dust, * (e) the Earth's core, 6. Which of the following statements is not true about the event(s) that caused the extinction of the dinosaurs? * (a) it caused the extinction of all land animals and plants, * (b) It ended the Cretaceous period * (c) it is thought to have been at least partly caused by impact of a meteorite, * (d) extinctions occurred on land and in the oceans, * (e) it was a global event 7. The Alvarezes were not out to determine the cause of the end-of-Cretaceous extinction, but instead intended to measure sedimentation rates. Based on their original plan to study sedimentation rates, which of the following statements is true? * (a) The higher the concentration of Ir in the sediment, the slower the sedimentation rate, * (b) The thicker the layers of sediment, the greater the sedimentation rate, * (c) the lower the concentration of Ir, the slower the sedimentation rate * (d) they did not expect any relationship between the amount of Ir and the sedimentation rate, * (e) they expected to find the effect of meteorite impacts in the sediments 8. What was the initial observation made by the Alvarezes that led to the meteorite impact hypothesis? * (a) the extreme thickness of the clay layer, * (b) a very low amount of Ir in the clay layer, * (c) the strange composition of the clay minerals in the clay layer, * (d) a very high amount of Ir in the clay layer * (e) the lack of any Ir in the clay layer, 9. Today, how many locations on Earth have evidence of a meteorite impact that happened at the K-T boundary? * (a) none, * (b) one, * (c) three, * (d) about a dozen (12) * (e) more than a dozen 10. After the Alvarezes discovered the high amount of Ir in the K-T clay layer, why did they not publish their results/hypothesis right away? * (a) They doubted their Ir analyses, * (b) they wanted to look for evidence of tsunamis, * (c) another research group had made the same discovery, * (d) a colleague recommended they analyze Ir at other sites, * (e) they wanted to wait until more people accepted their hypothesis 11. In the original 1980 paper, what prediction did the authors make that they themselves tested and confirmed? * (a) that no dinosaurs should be found above the clay layer * (b) that the crater should be in the Yucatan Peninsula, * (c) that tsunami deposits should be found, * (d) that the clay layer should have a different composition as clay elsewhere in the limestones, * (e) that melt spherules should be found nearby, 12. Tiny "spherules" (microtektites) have been found at the K-T boundary and at other impact sites. What is the origin of these spherules? * (a) they are tiny fragments of the meteorite, * (b) their origin is still unknown * (c) they are the remains of critters that died out during the impact, * (d) they are solidified droplets of rock melted due to the meteorite impact * (e) they are pieces of Iridium, 13. According to the astronomer Carl Sagan, “Extraordinary claims require...” what in order for those claims to be taken seriously? * (a) extraordinary time to be proven, * (b) extraordinary predictions from the claim, * (c) an extraordinary amount of people claiming the same thing, extraordinary evidence, * (e) all of the above 14. Below is the data published by the Alvarezes in their Science paper, which shows the concentration of Ir (in parts per trillion) in the samples versus the position of the samples in meters in the sedimentary rock. At what approximate position does the K-T boundary occur? * (a) 0 m, * (b) around 20 m * (c) 150 m, * (d) 305 m, * (e) 348 m 15. What is one example of how scientists have been testing whether the meteorite impact (which was pretty sudden) or whether the Deccan volcanism (which lasted about 1 million years at the end of the Cretaceous) was the main cause of the mass extinction at the end of the Cretaceous period? * (a) By measuring the Ir content of fossils, * (b) by looking at how rapidly species died out, * (c) by measuring the paleomagnetism in the clay layer, * (d) by looking at how many species died in total, * (e) all of the above 16. The lithosphere consists of: * (a) asthenosphere and crust * (b) asthenosphere and mantle * (c) inner core and outer core * (d) crust and uppermost mantle * (e) crust and outer core 17. The difference between lithosphere and asthenosphere is defined as a difference in * (a) composition * (b) strength * (c) pressure * (d) water content * (e) plate boundary 18. The main factor causing the difference in lithosphere and asthenosphere mentioned above is * (a) pressure * (b) silica content * (c) water content * (d) magnetism * (e) temperature 19. Which of the following comes closest to the average speed of the tectonic plates on Earth? * (a) a few inches or cm per year * (b) a few feet/decimeters per year * (c) a few yards/meters per year * (d) a few inches/cm per million years * (e) a few feet/decimeters per billion years 20. What type of plate boundary existed between India and Asia prior to their collision? * (a) convergent * (b) divergent * (c) transform * (d) there was no plate boundary between India and Asia * (e) hot spot boundary 21. The most volcanically active (but non-explosive) regions on Earth are associated with? * (a) convergent boundaries * (b) divergent boundaries * (c) transform boundaries * (d) hot spots * (e) all of the above 22. A global map of earthquakes would look most like * (a) a map of hot spots * (b) a map of the continents * (c) a map of the continental shelves * (d) a map of the tectonic plate boundaries * (e) a map of the mid-ocean ridges 23. The most famous transform plate boundary is the San Andreas Fault. Another example of a transform plate boundary is * (a) The Hawaiian Island chain * (b) The New Madrid seismic zone * (c) The Appalachian Mountain chain * (d) The Dead Sea area on the west side of the Arabian plate * (e) The Caldonide Mountain chain 24. The deepest part of the ocean floor is at the Mariana trench. What are trenches due to? * (a) the lack of magmatism in that area of the seafloor. * (b) a depression due to the down-bending of a subducting plate as it subducts * (c) a deep depression where two plates pull apart. * (d) a large area of erosion where the seafloor is damaged by faulting * (e) faulting at a transform boundary 25. The outer core of the Earth is made up mostly of * (a) liquid iron, * (b) dense silicates, * (c) liquid silicates, * (d) solid iron, * (e) the liquid equivalent of the mantle 26. The Earth's mantle (the asthenosphere part), where most magmas come from, is made up mostly of * (a) liquid iron * (b) solid iron * (c) liquid silicates (rocky material) * (d) solid silicates * (e) none of the above 27. Why are there volcanoes in the Pacific Northwest of the US (the states of Washington, Oregon, and northern California? Because * (a) there is a convergent plate boundary * (b) there is a divergent plate boundary * (c) there is a transform boundary * (d) there is a hot spot * (e) the continent is breaking apart there 28. Which of the following statements is true? * (a) The desire of plates to sink into the asthenosphere is the main driving force of plate motions * (b) Lithosphere is colder than asthenosphere * (c) volcanoes occur at divergent boundaries, convergent boundaries, and hot spots * (d) Mid-ocean ridges mark divergent boundaries in the oceans * (e) all of the above 29. Which of the following statements is false? * (a) Some plates contain continents, other plates do not * (b) Crust, mantle, and core are Earth layers differing in composition * (c) subduction zones are the downgoing parts of Earth's convection system * (d) The Hawaiian islands cannot be fully explained by plate tectonics alone * (e) The Earth's crust is the main strong outer layer of the Earth. 30. When mantle plumes were hypothesized, what prediction of that hypothesis was tested (and confirmed) by seismology (by measuring the speed of earthquake waves through the earth)? * (a) All the Hawaiian islands should have the same seismic velocities * (b) Cold subducting plates should be found beneath hot spots * (c) Seismic speeds should increase with depth * (d) Hot spots like Hawaii should be underlain by slow velocity mantle * (e) The speed of seismic waves should decrease away from the Big Island of Hawaii 31. Which of the following characteristics of hot spot volcanoes makes them different from subduction zone volcanoes? * (a) They erupt volcanic rock * (b) They form a line of volcanoes * (c) They occur at plate boundaries * (d) Their ages get older in a certain direction * (e) The melting is caused by addition of water 32. If one finds extensive glacier deposits in some ancient rocks, what would you expect their magnetic inclination to be? * (a) Close to horizontal (zero) * (b) Not too high and not too low * (c) Near vertical (90 degrees) * (d) One would not expect any relationship between the magnetic inclination and the presence of abundant glacial deposits * (e) It would depend on how old the deposits are 33. A tectonic plate shaped like a square is moving west (to the left). What type of plate boundary would you most likely expect on its East/right side? * (a) convergent, * (b) divergent, * (c) transform, * (d) cannot be determined, * (e) hot spot boundary 34. Which of the following is a reason, factor, or contributing cause of the "magnetic stripes" that were discovered on the seafloor parallel to the mid-ocean ridges? * (a) symmetric movement of the plates away from the mid-ocean ridge * (b) creation of new ocean floor by volcanism on the seafloor, * (c) reversals of the Earth's magnetic field * (d) the strength of the magnetic field at any point is the sum of the Earth's magnetic field at that point and the field from the rocks underneath * (e) all of the above 35. Why are stratovolcanoes or composite volcanoes called such? * (a) they have highly viscous magma * (b) they are composed of both lavas and pyroclastics * (c) they are made up of stratified basalt lava * (d) they are usually very tall * (e) they usually erupt ash into the stratosphere 36. Which of the following combinations of magna composition and volatile (e.g., water) content results in lava fountains? * (a) fluid magma with little volatiles * (b) fluid magma with a lot of volatiles * (c) viscous magma with little volatiles * (d) viscous magma with a lot of volatiles * (e) b and c 37. Which of the following combinations of magma composition and volatile content results in thin, long lava flows? * (a) fluid magma with little volatiles * (b) fluid magma with a lot of volatiles * (c) viscous magma with little volatiles * (d) viscous magma with a lot of volatiles * (e) a and c 38. Which of the following will make magma more fluid (i.e., lower its viscosity)? * (a) reducing the amount of silica * (b) lowering the temperature * (c) increasing the size of the volcano * (d) increasing the pressure * (e) all of the above 39. In the figure below, curve “f” represents the temperatures where melting begins for “dry” rocks in the mantle at various depths/pressures (melting will happen to the right of this curve; no melting to the left). Which curve best represents the average geotherm (increase in actual T with depth)? * --- INCREASING TEMPERATURE ----> * <----- INCREASING PRESSURE and DEPTH 40. Which curve best represents the actual temperatures where melting occurs where plates are pulling apart and there is decompression melting? * (a) a (b) b (c) c (d) d (e) e 41. All the granite in Yosemite National Park is thought to be part of which igneous feature? * (a) the former magma chambers of stratovolcanoes, * (b) sills that were intruded into the crust, * (c) the roots of cinder cones, * (d) the underground source of an ancient flood basalt, * (e) the root of a volcanic neck 42. The most abundant and most active (but non-violent) volcanism is happening at mid-ocean ridges. Why are magmas generated at these locations? * (a) increase in pressure and increase in temperature in the crust causing melting * (b) release of large amounts of CO2 into the crust * (c) pressure release melting of the asthenosphere * (d) heating of the mantle from meteorite impacts * (e) “wet melting” or addition of water at subduction zones 43. The volcanic phenomenon/product that can travel the farthest distance on the Earth's surface and has caused the most death and destruction is * (a) pahoehoe lava flows, * (b) pyroclastic flows, * (c) lahars, * (d) volcanic spines, * (e) lava domes 44. The event that immediately triggered the explosive eruption of Mt. St. Helens on May 18, 1980 was * (a) rise of magma underneath the volcano * (b) a landslide caused by an earthquake * (c) a lahar * (d) subduction off the coast * (e) addition of water to the magma chamber 45. Subduction zone volcanoes have high water contents which partly causes their explosivity. What is the origin of this water (where does it come from)? * (a) It is rainwater that enters the magma chamber * (b) It is groundwater that enters the magma chamber * (c) It is water found throughout the mantle that was locked in when the Earth formed * (d) It is water formed when oxygen combines with hydrogen in the magma chamber * (e) It is seawater that is in minerals in the subducted oceanic crust 46. An igneous rock is composed entirely of tiny crystals that are not visible with the naked eye. This implies that: * (a) the rock formed from magma, * (b) the magma cooled very rapidly, * (c) the lava erupted slowly, * (d) the lava erupted in the form of a long lava flow, * (e) the rock comes from the mantle 47. Numerous holes or small voids in a volcanic rock are usually frozen bubbles that were caused by * (a) crystals, * (b) pyroclastic material, * (c) magma, * (d) slow cooling, * (e) volatiles/gases 48. Which of the following lavas is the result of the most fluid lava? * (a) pahoehoe, * (b) aa, * (c) block lava, * (d) lava dome, * (e) any of the above could be due to very fluid lava 49. Explosive / violent eruptions are characteristic of or most abundant at which type of tectonic plate boundary? * (a) convergent boundaries, * (b) divergent boundaries * (c) strike slip boundaries, * (d) hot spots, * (e) all of the above 50. In the National Geographic video shown in class, there was one very bad error (that is quite commonly believed) that was shown. What is this error? * (a) That volcanoes can be found everywhere * (b) That the Earth's mantle is all liquid magma * (c) That the most explosive volcanoes are found on the seafloor * (d) That magmas come from the Earth's core * (e) That magmas are causing the plates to move --- end of exam ---