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Study Guide #1About half the exam questions, with the exception of bonus questions, will be taken from the Study Guides. Therefore, answering Study Guide questions is good practice for the exams. Students have the option of turning in their answers to any 2 essays to be graded. If they are turned in on time (February 11), you will get the graded questions returned to you the lecture before the exam. You will get up to 6 BONUS POINTS if your answers are correct. We recommend that all students do this because it will help you to learn the best way to answer exam questions for full credit. Assignments may be turned in at lecture, or at Jennifer Reynolds’ office, or e-mail. If the latter, send attachments ONLY as text or RTF files, NOT as word processor files like Word, Works, or Wordperfect. Some hints on how to answer exam questions: When I use the words "How", "Why" or "Describe" or "Discuss" in a question, I am looking for something more than a 1 or 2-word answer. For example, the following answer to the question "Name and briefly describe the sources of three major types of ocean bottom sediment" would receive full credit: Lithogenous sediments are produced by weathering of rocks on the continents and are carried to the oceans by rivers or winds. 2) Biogenous sediments are the tiny shells of microscopic marine animals or plants that grow mostly in the ocean's surface waters. 3) Hydrogenous sediments are formed by precipitation of chemicals from seawater or sediment pore water. An answer that would receive only about half-credit would be: Lithogenous-rocks, biogenous-organisms, hydrogenous-water. If I use the words "list", "what" or "where" then an answer of a few (correct) words is OK. For example: List at least one similarity and one difference between the ocean 4 billion years ago, soon after it had formed, and the present-day ocean. Similarity (any of these): The ocean was salty, the ocean had similar salt composition (mostly sodium chloride), the ocean was comparable in size to the present-day ocean, the temperature of most of the ocean was between 0 and 100 degrees Centigrade. Differences (any of these): The ocean was devoid of life, the ocean (and atmosphere) lacked free oxygen, the ocean had a lot of dissolved iron. More detail is required for essay questions than for short-answer questions. An example "perfect" answer for an essay question which will not be on the exam is: Describe the major events in the evolution of life on Earth, from 3.8 billion years ago to the present. About 3.8 to 4 billion years ago, the earth already had a large, salty ocean and a temperature range (0-100° C) not too different from that today. The atmosphere lacked oxygen, but otherwise was not unlike that today, with nitrogen, argon, carbon dioxide and water vapor. A source of energy (hot volcanic rock or lightning are two examples) caused some of the chemicals present in the atmosphere or ocean to react to form substances like the simplest building blocks of life...amino acids and nucleic acids. Polymers of various kinds apparently also formed. It is not understood how these substances assembled to form the first living organisms; perhaps mineral surfaces provided a "template". But fossil evidence shows that by 3.5-3.8 bybp, bacteria-like organisms similar to blue-green algae still living today had evolved. Bacteria (prokaryotes) were apparently the only type of life for the first 3 billion years. About 2.5 to 2.2 bybp, enough blue-green algae were present, producing oxygen, that free oxygen became a substantial component of the atmosphere. About 1 bybp, eukaryotic organisms (those with complex internal cell structures like mitochondria, chloroplasts, and a nucleus) evolved. About 0.57 bybp, the Cambrian Explosion occurred, the relatively sudden appearance of a rich fossil record including shelled organisms and representatives of all of the metazoan (multicellular) animal phyla that exist today. By the Devonian (408-360 million years ago) there were abundant fishes in the oceans and widespread forests on land. From the Cambrian onward, the fossil record is complete enough to provide evidence of many mass extinctions, including one about 250 million years ago and another about 65 million years ago at the end of the age of dinosaurs. Following these mass extinctions, there is a proliferation of new species. By about 500 million years ago, vertebrates such as fishes had evolved. Land plants appeared about 440 million years ago, reptiles 360 million years ago, and mammals 250 million years ago. Fossils of human ancestors date to 2-3 million years ago, and anatomically modern humans to 50,000 years ago. Note: The key points are in italics, others would help your answer...and could compensate for missing items...but are not be required. I normally do not require that specific dates or ages be memorized, but would require that you describe events in the correct order. THIS IS THE BEGINNING OF THE STUDY GUIDE (finally). The questions are in approximate chronological order, with respect to the lectures, within each category (Short Answer, Essay). Short Answer. You should be able to answer these questions with two or three sentences. Some questions (as noted) can be answered most easily with a drawing or diagram. 1. What are the two most abundant elements in the Universe? Where did they come from? 2. How and where were the elements which are heavier than helium, but lighter than iron, formed? (Examples of this group of elements are carbon and oxygen.) 3. How and where were the elements heavier than iron formed? (Examples of this group of elements are silver, lead, and uranium). 4. Where did sea salts come from? Briefly describe how the ocean became salty, around 4 billion years ago, as the oceans formed. 5. List at least one similarity and one difference between the ocean 4 billion years ago, soon after it had formed, and the present-day ocean. 6. What are stromatolites? Why are they important? 7. Draw a time line from 4 billion years to the present, showing the timing of these major events in the Earth's history: a) Formation of a solid crust and liquid oceans. b) Age of first fossil evidence of life. c) Age of "redbeds", indicating the presence of substantial free oxygen in the Earth's atmosphere. d) Age of first fossils with hard outer shells (the "Cambrian Explosion"). e) The Cretaceous-Tertiary Boundary, when dinosaurs became extinct, along with about 90% of marine species. f) Age of first fossil evidence of modern humans. 8. Where did the oxygen in the atmosphere come from? Why did it take at least 2 billion years for it to appear, after the Earth formed? 9. What was the Cambrian Explosion? What is one possible trigger, or cause, of the Cambrian Explosion? 10. Why are mass extinctions important in the evolution of life on Earth? (Give at least two reasons.) 11. How are the ages of ancient rocks, sediments, and organisms measured? 12. Describe the Earth's hydrologic cycle. A diagram may be the easiest way to do this. 13. Draw a cross-section of the ocean margin, extending from the continent to the deep-sea floor, and label the continental rise, continental shelf, ocean floor, continental slope, and shelf break. Your diagram should show the relative slopes of the zones correctly, that is, you should show where the elevation of the margin changes rapidly and where the change is more gradual. 14. Where are submarine canyons found, and how do they form? 15. Where are abyssal plains found, and how do they form? 16. Name and briefly describe the source of the 3 major types of ocean bottom sediment. (Do not use the rare cosmogenous (extraterrestrial) sediment type in your answer.) 17. Name and briefly describe the source of the 2 major types of biogenous oozes. 18. Why are there almost no calcareous oozes below about 4000 meters depth in the oceans? 19. Terrigenous sediments are usually coarsest (largest in grain size) near land, and become progressively finer farther from shore. Why does this pattern occur? 20. Match the sediment accumulation rate with the place where it occurs (draw straight lines):
21. Describe an example of the ocean’s (or earth’s) history that is recorded in marine sediments. 22. Draw a labeled diagram showing the structure of the Earth's interior and the major layers. 23. Describe two kinds of information that have helped scientists to learn about the structure and composition of the Earth's interior. 24. Describe two major differences between the Earth's oceanic crust and continental crust. 25. Describe two major differences between rocks of the Earth's crust and those of the mantle. 26. What is paleomagnetism? Briefly describe the sea floor pattern of paleomagnetism that was some of the first strong evidence for plate tectonics. 27. What are the 3 major types of tectonic plate boundaries? In each case, give the name of the boundary and describe (or illustrate) the directions in which the plates are moving. 28. What was Pangaea? 29. What are hydrothermal vents, and where are they found? 30. What is a scientific hypothesis? 31. Briefly describe the difference between scientific observations and scientific experiments. 32. Alaska has a wide variety of geological formations, including at least six major terranes, with vastly different ages, structures, and mineral compositions. Why? 33. Draw the chemical structure of water (at least two molecules). Show and label at least one hydrogen bond. 34. Explain the phrase, "latent heat of vaporization of water". 35. What is salinity? How is it measured? 36. List the two ions with the highest concentrations in seawater. Indicate which ion is a cation and which is an anion. Which salt consists of a combination of these two ions (spell out the name, not just the chemical formula)? 37. Explain what oceanographers mean when they say that a dissolved ion or salt is conservative in seawater. 38. Give an explanation for the observation, based on evaporite composition, that sea salt concentration and composition have been nearly constant for about the last 1 billion years. Essay questions, usually require answers of about 10 sentences in length. 39. Describe the important events during the origin of the Earth and the oceans, starting with an interstellar cloud of dust and gases (a nebula) and ending with the early earth, just before life originated (about 4 billion years ago). 40. Describe at least three types of evidence for plate tectonics, that is, evidence that the Earth's crust is formed of moving "plates". 41. Explain why (a) siliceous oozes are found mainly in sediments of the equatorial Pacific and around Antarctica, (b) calcareous oozes are found mainly on mid-ocean ridges and rises, and are more common in the Atlantic than the Pacific, and (c) lithogenous sediments are found both on continental margins and in the deepest parts of the ocean. 42. What are 4 special or unusual properties of water? List the property, and explain why it is important in the oceans. 43. Outline the scientific method. Describe one well-publicized example of a scientific “discovery” that turned out to be wrong. Include discussion of the way in which the scientific method was violated. |