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Geology 141 Name . Spring, 2005 2005 2 March, GE141: Physical Processes of Planet Earth First Hour Examination This examination is worth 150 points, or 15.0% of your overall semester grade. Exams will be graded as quickly as possible; your individual point total will be entered on the last page to ensure that only you know how well you did on the exam, unless you choose to divulge that information to others. "Often people attempt to live their lives backwards: They try to HAVE more things or more money, in order to DO more of what they want, so they will BE happier. The way it actually works is the reverse. You must first BE who you really are, then DO what you need to do, in order to HAVE what you want." ---Margaret Young Geology 141, Spring, 2005 First Hour Examination ... Page 2 ... INSTRUCTIONS: PLEASE read the questions CAREFULLY and completely. If you do not understand something as it appears on the exam, PLEASE ASK FOR CLARIFICATION!! It is to YOUR benefit to do so. Please respond to each question in the most appropriate fashion. Please make your responses concise and to the point, but thorough; use sketch diagrams any place you believe that they may help explain your response. There should be ample space provided for an adequate response to each question; KINDLY RESTRICT YOUR RESPONSES TO THE SPACE PROVIDED. PLEASE ALSO remember that I CANNOT give any credit for responses I can't read! The number of points for each question is indicated in parentheses after the question. (And PLEASE remember as well that, as promised on the syllabus, as painful as it is for me, I WILL deduct a point each time I see "volcanoe" or "techtonic!") 1. Approximately when do scientists believe the Universe came into existence, in the "Big Bang?" years ago (2 points) 2. About when do scientists believe OUR solar system, and the Earth, came into existence? years ago (3 points) 3. What is the direct evidence that our solar system is a second-generation star system (see #4 before become verbose!)? (2 points) 4. WHY does this indicate that our solar system was created from the debris of a preexisting star? (3 points) 5. The most abundant element in the Earth as a whole (~35% by weight) is (2 points) 6. The most abundant two elements in the Earth's crust (~47% by weight and ~27% by weight, respectively) are and (3 points: 2-1) 7. The dominant mineral group in the Earth's crust, comprising some 95% by weight of all crustal rocks, is the (3 points) 8. The only OTHER mineral group that's most important for its bulk in the crust, comprising about 3% of all crustal rocks (or over half of all those minerals not in the group you identified in #7), is the Geology 141, Spring, 2005 First Hour Examination ... Page 3 ... (2 points) 9. What is the difference between silicon and silica? (5 points) 10. What are two major pairs of elements that are important in ionic substitutions in the dominant mineral group that makes up the outermost layer of the Earth? (Match one major element with another that commonly substitutes for it in the crystal structures; 4 points - 1 point each.) a. and . b. and . 11. What are the four defining criteria a substance must meet to be considered a mineral? (6 points: 2-2-1-1) 1. 2. 3. 4. 12. What is the elemental composition of the core of the Earth? What is the difference between the INNER core and the OUTER core? (5 points: 3-2) Composition: Difference: 13. How thick is the oceanic crust? How thick is typical continental crust? km. (2 points) km. (3 points) Geology 141, Spring, 2005 14. First Hour Examination ... Page 4 ... Identify THREE major lines of evidence that support the combined theories of continental drift and plate tectonics, and indicate clearly HOW each of these kinds of evidence support those theories. (10 points) 1. 2. 3. Geology 141, Spring, 2005 First Hour Examination ... Page 5 ... 15. What major plate tectonic processes are taking place at the Mid-Oceanic Rise and Ridge System, and why are they important? (10 points) 16. What are the three major categories of rocks, and what is a defining characteristic of each? (10 points: 4-3-3) 1. 2. 3. Geology 141, Spring, 2005 First Hour Examination ... Page 6 ... 17. Three major factors determine the viscosity of a magma. What are those three factors, and how does each affect the viscosity? (i.e., Does more of a given factor INcrease or DEcrease the viscosity of a given magma?) (List the factor first, then indicate in the space provided whether an increase in this factor makes the magma more or less viscous; 10 points) 1. 2. 3. 17. What part of the Earth is the source for all mafic magmas, like those in Hawai'i, Iceland, the Mid-Oceanic Rise and Ridge system, or the Galápagos Islands? (5 points) 18. In a porphyritic volcanic rock composed mainly of hornblende, Na-plagioclase and a potassium feldspar, which of these is MOST likely to be found as a phenocryst, and why? (10 points) 19. What is believed to be the mechanism by which the Hawaiian Island chain has come into existence? Why is this NOT an island arc system? (10 points) Geology 141, Spring, 2005 First Hour Examination ... Page 7 ... 20. Why are there so many volcanoes in Ecuador and throughout the Andes Mountains, as well as in SW Alaska, Oregon, and Washington? (10 points) Geology 141, Spring, 2005 First Hour Examination ... Page 8 ... 21. Please fill in the names of the parent magma types as well as of the rocks that are produced by crystallization of each of the three major magma types, both volcanic and plutonic. (9 points) Magma type | Silica content | | | | >65% | | | | | | 55-65% | | | | | | 45-55% | | | Volcanic Rock | | | | | | | | | | Plutonic Rock . . . . 22. If mantle plumes are responsible for both the relatively benign eruptions of Hawai'i and the catastrophically explosive eruptions of the Yellowstone and Long Valley Calderas, why are the resulting eruptions so very, very different? (6 points) Geology 141, Spring, 2005 First Hour Examination ... Page 9 ... 23. What is the difference between DIKES and SILLS as plutonic igneous rock bodies? (Use a sketch diagram is you think this will help!) (5 points) 24. On the maps on the following page (the maps are printed back-to-back), locate precisely each of the following localities or features. FOR SMALL FEATURES OR LOCALITIES, use a sharp arrow drawn from your label to the feature, so there can be no doubt about what you are labeling. PLEASE remember that IT IS TO YOUR BENEFIT that your label is clear enough that there is NO question as to your meaning or intent! (10 points, 1 point each) And YES, all labels must be correctly spelled for credit! [ Since all you have to do is copy the name from the list below! ] On the map of the U.S. & Canada: Nova Scotia Washington, D. C. Alberta Arizona Cascade Range On the map of the world: Andes Mountains Peru London, England Albania Bulgaria Grade on exam: __________________ out of 150 possible*. * If this is below 100, please see me within the next week !!! PLEASE NOTE: After exams are graded, I will return your exam ONLY to you. It will not be released to friends, roommates, your lab partner, or anyone else. This is to ensure YOUR security and confidentiality.