ESS 101 Midterm Autumn 2005 Student #:

ESS 101 Midterm Autumn 2005 Student #: Name VERSION A Provide the best answer for the following multiple choice questions. There are 49 regular test questions and five bonus questions. The bonus questions can only help your score. Circle the correct answer on your test paper and hand it in along with your scantron form. Answers provided at the end of the exam. 1-3 Match the magma type with the appropriate tectonic setting where it likely forms. 1. Iceland a. basalt 2. Sierra Nevada batholith b. granite 3. Phillipine Islands c. andesite d. peridotite e. andalucite 4. The Columbia Plateau is composed of rock rich in: a. granite b. gabbro c. peridotite (>90% olivine) d. basalt e. andesite 5. The melting temperature of granitic magma (wet melt) : a. increases as pressure is reduced (as it rises). b. decreases as pressure is reduced (as it rises) c. does not change as pressure changes d. is not dependent upon the composition of the magma 6. A partial melt of the asthenosphere will not rise toward the surface because. a. because of centrifugel forces b. earth's magnetic field c. convection cells in the outer core d. the melt is less dense than the surrounding rock e. the above question is incorrect because an asthenospheric melt will rise towards the surface 7. Aa basalts. a. are blocky textured flows that form as the viscosity increases during degassing b. are blocky textured flows that form as the viscosity decreases during degassing c. are ropey textured flows that form as the viscosity increases during degassing d. are ropey textured flows that form as the viscosity decreases during degassing as aa is not a real word in geologic vocabulary 8. When two ocean plates converge. a. the younger plate will be subducted b. the lighter plate will be subducted c. the older plate will be subducted d. a collision mountain belt will form 9. The most widely accepted explanation for the earth's magnetic field is. a. movement of electrons in the molten iron of its outer core b. movement of electrons in the molten iron of its inner core c. small magnetic mineral present in its crust d. the earth does not have a magnetic field e. none of the above are correct

2 10. What kind of plate margin exists today in East Africa? a. divergent margin b. convergent margin (ocean-continental collision) c. convergent margin (ocean-ocean collision) d. transform margin e. collision margin (continent-continent) 11. What type of volcanic rock would incorporate lithic fragments during the eruption. a. andestite b. volcanic tuff c. granite d. obsidian e. pumice 12. Why does potassium feldpar develop cleavage planes yet it is a framework silicate mineral with all its oxygen atoms shared between tetrahedra? a. this mineral does not cleave. b. this mineral has an aluminum atom in some of its tetrahedra which requires additional ionic bonds with potassium atoms c. this mineral is not a silicate mineral and consists of weak ionic bond between d. the mineral cleaves between covalent bonds separating sheet pairs e. none of the above are correct 13. flows from Mount Vesuvius obliterated the Roman city of Pompeii in 79AD. a. Lava b. Pyroclastic c. Mud d. Lahar e. Glacier 14. Magnetic minerals that crystallize in a lava flow erupted near the North Pole today will. a. be oriented perpendicular to the surface of the lava flow b. be oriented parallel to the surface of the lava flow c. be oriented at an oblique angle (not perpendicular or parallel) to the surface of the lava flow d. all of the above answers are correct 15. Rank the chemical bonds forming minerals from weakest to strongest a. ionic, Vanderwahl, covalent b. Vanderwahl, covalent, ionic c. covalent, Vanderwahl, ionic d. ionic, covalent, Vanderwahl e. Vanderwahl, ionic, covalent 16. What are the two most common elements comprising rocks of the crust and mantle. a. Iron (Fe) and Nickel (Ni) b. Iron (Fe) and Magnesium (Mg) c. Hydrogen (H) and Oxygen (O) d. Silicon (Si) and Oxygen (O) e. Oxygen (O) and Carbon (C)

3 17. How does the silicate tetrahedron achieve charge balance? a. it will share electrons between oxygen atoms b. it will form ionic bonds with available cations c. it will form Van der Waal bonds with available cations d. all of the above are correct e. only answers a and b are correct 18. Why do the large Jovian planets have molecular hydrogen in their atmospheres, but the smaller terrestrial planest do not? a. The Jovian planets are further from the sun and the hydrogen gas can condense and be held by gravity. b. The terrestrial planets have a large component of molecular hydrogen in their interiors. c. The Jovian planets do not have molecular hydrogen in their respective atmospheres. d. all of the above answers are correct. 19. Most mined iron ore occurs in the mineral group. a. sulfide b. halide c. oxide d. carbonate e. silicate 20. Most metallic ore bodies, such as lead, silver and copper occur in the mineral group. a. sulfide b. halide c. oxide d. carbonate e. silicate 21. What is the significance of (OH) in the amphibole crystal structure? a. it is due to alcohol being degassed from the primitive mantle b. it is water likely formed in the primitive mantle c. it is water likely incorporated during the subduction process d. it is water resulting from asteroid impacts e. it is alcohol stashed during prohibition 22. Why does the topographic expression of the Hawaiian Island become progressively lower from the Big Island to the island lying northwest? a. the topographic expression of all the Hawaiian Islands is the same b. the ocean lithosphere is less dense to the northwest and it floats higher c. there is a subduction zone to the northwest drawing the ocean crust downward d. the Big Island has a segment of continental crust within its interior e. the ocean lithosphere is lighter over the hotspot and it floats higher 23. Arrange the compositional zones of the earth according to their respective density (lightest to densest). a. continental crust, ocean crust, mantle, outer core, inner core b. ocean crust, continental crust, mantle, outer core, inner core c. inner core, outer core, mantle, continental crust, ocean crust d. outer core, mantle, ocean crust, continental crust, inner core e. inner core, outer core, mantle, ocean crust, continental crust 24. What kind of tectonic setting is represented by Yellowstone Park? a. divergent margin b. convergent margin (ocean-continental subduction) c. convergent margin (ocean-ocean subduction) d. hotspot e. collision margin (continent-continent)

4 25. Meteorites that strike the earth are predominantly composed of? a. iron-nickel and silicate minerals b. hydrogen sulfide and silicate minerals c. carbon-based materials and iron-nickel d. only material found in the earth s core e. mainly materials found only in continental crust 26. Why do seismic waves decelerate in the low velocity zone? a. it is composed of low density liquid iron b. the low velocity zone is at the pressure melting temperature for the earth s mantle c. seismic waves do not slow down in the low velocity zone d. the low velocity zone represents a part of the earth s mantle that has a unique composition e. there is no low velocity zone below the surface of the earth 27. During differentiation of the earth into its compositional zones heat was generated from. a. kinetic energy of impacting planetesimals b. compressional heating during condensation c. radioactive heating d. all of the above are correct e. only answers a and b are correct 28. What mechanism have geologists proposed to explain the uplift of the Colorado Plateau and the rifting of Nevada and Utah? a. a spreading ridge was subducted under California and is now upwelling beneath the Basin and Range b. a continental collison occurred 45 million years ago that caused the uplift of the Colorado Plateau c. a bolide impact occurred 27 million years ago that caused the rifting of Nevada and Utah d the Colorado Plateau has not been uplifted in recent geologic history, nor is Nevada and Utah rifting e. the causes of these two geologic events are unknown and no theories have been proposed 29. Transform plate boundaries are typically associated with. a. convergent margins where the descending plates slows down during subduction b. convergent margins where the descending plates speeds up during subduction c. divergent margins where the rate of spreading is different along segments of the spreading ridge d. divergent margins where the rate of spreading is the same along segments of the spreading ridge. 30. The cause of volcanism observed in the Cascades is similar to that of. a. Yellowstone Park b. the Phillipines c. the Columbia Plateau d. Himalaya Mountains e. the Hawaiian Islands 31. A shield volcano has a lower slope angle than a strato (composite) volcano because. a. its basaltic lava flows have higher viscosities than the andesitic flows of strato volcanoes b. its basaltic lava flows have lower viscosities than the andesitic flows of strato volcanoes c. the shield volcano is smaller than the strato volcano and cannot achieve the same slope angle d. it has more water content which lowers the melting temperature e. answers b and d are both correct 32. What is the significance of the change in direction of the Hawaiian Island and the Emperor Seamount chains? a. the tectonic plate on which both island chains sit changed directions b. each island chain formed from two different hot spots. c. a single hot spot moved beneath the tectonic plate d. the Hawaiian Islands formed over a hot spot volcanism while Emperor Seamounts are part of a mid-ocean spreading ridge

5 33. Which tectonic margin would tend to have only shallow focused earthquakes? a. divergent b. transform c. convergent d. all of the above answers are correct e. only answers a and b are correct 34. Basaltic composition magma can form. a. at sea floor spreading zones b. at continental rift zones c. above hotspots d. back arc spreading basins e. all of the above tectonic settings 35. P-waves as they travel through the outer core. a. are absorbed b. decelerate c. accelerate d. reverse e. rebound 36. How can we best explain the fact that the inner and outer cores are both composed of metallic iron and nickel yet the outer core is liquid and the inner core solid? a. the outer core is solid and the inner core is solid b. the melting temperature for iron-nickel is greater than the geothermal gradient temperature in the outer core c. the melting temperature for iron-nickel is the same as the geothermal gradient emperature in the outer core. d. the melting temperature for iron-nickel is lower than the geothermal gradient temperature in the outer core. e. the actual temperature of the outer core is greater than the inner core's actual temperature. 37. How can mantle rocks be brought to the surface of the earth, such as in the Cascades or Fidalgo Island? a. they are brought to the surface along mantle plumes (hot spots) b. they are brought to the surface in magma bodies related to subduction c. they are squeezed to the surface along suture zones where collisions occur d. all of the above answers are correct 38-40. Use the rock-composition diagram shown below to answer questions -. Answer the following questions (-) based on the igneous rock classification chart shown below:

6 38. An aphanitic (volcanic) rock composed of 5% quartz, 65% plagioclase, 25% amphibole and 5% pyroxene would be classified as. a. basalt b. diorite c. andesite d. rhyolite e. granite 39. An aphanitic (volcanic) rock composed of predominantly calcium-rich plagioclase and pyroxene would be classified as. a. basalt b. diorite c. gabbro d. rhyolite e. granite 40. Diorite may contains potassium feldspar. a. 0% b. 10-20% c. 30-40% d. 40-50% e. 70-90% 41-43. Magma is being erupted from a divergent margin. 41. What type of magma is largely produced at this setting? a. rhyolite b. obsidian c. andesite d. pumice e. basalt 42. This type of tectonic setting can be found? a. only beneath ocean basins b. only beneath continents c. along the San Andreas Fault d. beneath ocean basins and continents 43. What is the main source of the erupted lava? a. partial melt of the asthenosphere b. partial melting of the subducting ocean crust and marine sediment c. partial melting of the continental crust d. mantle plumes e. none of the above are correct 44. As magma crystallizes into igneous rock the residual melt. a. will become more mafic (Fe-rich) b. will be come more felsic (silica-rich) c. will yield more explosive eruptions d. answers a and c are both correct e. answers b and c are both correct 45. What volcanic hazard is most commonly generated from eruptions of Mount Rainier? a. pyroclastic flows b. mudflows (lahars) c. lava flows

7 d. all of the above hazards are commonly associated with Mount Rainier eruptions e. none of the above hazards are common for Mount Rainier because it is an extinct volcano Lab Questions 46. In the geologic techniques lab each group completed a topographic cross-section of Icicle Creek and Wenatchee River. What profile shape was indicative of a river valley? a. V-shaped b. Y-shaped c. U-shaped d. depends exclusively on the bedrock lithology 47. In the plate tectonics lab we observed that oceanic crust comprising the Juan de Fuca plate was being created at the spreading ridge at a rate the rate of its subduction beneath the North American plate? a. the same as b. less than c. more than d. not known compared to e. that is accelerating compared to 48. In the minerals lab the main diagnostic criteria for identifying the metallic mineral galena was. a. its high density b. its cubic cleavage c. its glassy appearance d. its gold color e. answers and a and b were both properties observed for galena 49. In the igneous rock lab we observed the rock andesite. It had a texture. a. coarse-grained b. fine-grained c. porphyritic d. glassy e. fragmental texture Bonus Questions (There are five bonus questions #50-54) Will be specific to a given lecture. Answers: 1-a 2-b 3-c 4-d 5-a 6-e 7-a 8-c 9-a 10-a 11-b 12-b 13-b 14-a 15-e 16-d 17-e 18-a 19-c 20-a 21-c 22-e 24-d 25-a 26-b 27-d 28-a 29-c 30-b 31-b 32-a 33-e 34-e 35-b 36-d 37-c 38-c 39-a 40-a 41-e 42-d 43-a 44-e 45-b 46-a 47-b 48-e 49-c

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