Ocean Sciences 101 The Marine Environment Midterm #1

Transcription

1 Part 1. Multiple Choice Questions. Choose the one best answer from the list, and write the correct letter legibly in the blank to the left of the question. 2 points each. 1. Many of the unique properties of water are attributed to the fact that water: A) contains hydrogen bonds B) exists in three phases at the Earth s surface C) is a polar molecule D) is hydrophobic E) requires heat to condense 2. If a chemical is not very abundant in the ocean but has a high rate of delivery to the ocean from land sources, it will have a residence time in the ocean and will become part of the seafloor sediments. A) long; quickly B) long; slowly C) short; quickly D) short; slowly E) variable; variably 3. Ptolemy was the first person (that we know of) to include on a map A) his signature. B) all of the continents. C) the oceans. D) latitude and longitude E) bathymetric contours. 4. Abyssal plains are created by A) vulcanism. B) sedimentation. C) seismic upheaval. D) hotspots E) None of the above are correct. 5. As the salinity of seawater increases, its A) density decreases B) heat capacity decreases C) residence time increases D) conductivity decreases E) residence time does not change. 6. A very important way to increase the settling rate of fine particles in the open ocean is via: A) carbonate dissolution B) deposit feeders C) precipitation D) fecal pellets E) wind

2 7. The particle size of terrigenous sediments generally with distance from shore. A) increases B) decreases C) stays the same D) become less uniform E) is less graded 8. Biogenous sediment is A) derived from rock. B) derived from plants and animals. C) always found at depths over 4500 m. D) always associated with deep-sea trenches. E) derived from the chemistry of the water. 9. The Challenger expedition tested all of the following hypotheses except: A) the theory of evolution B) the endosymbiosis hypothesis C) the emergence hypothesis D) the azoic hypothesis 10. The Meteor expedition A) collected information about the physics, biology, and chemistry of all the oceans B) documented the topography of the South Atlantic using an echosounder C) explored the Marana trench D) is an example of a deep sea drilling project 11. An active landmass margin than its trailing margin. A) is wider B) shows less tectonic activity C) is more stable D) typically has a rocky-intertidal coastline E) is characterized by wide, sandy beaches 12. Which of the following are found along subduction zones? A) oceanic trenches B) active Earthquake zones C) island arc systems D) All of the above are correct. E) None of the above are correct. 13. The San Andreas fault is an example of a A) transform fault B) convergent plate boundary C) divergent plate boundary D) rift valley E) hot spot

3 14. The oceans' youngest rocks are found A) at the hottest part of a rift zone B) on top of the basalt layer, far from spreading centers. C) adjacent to a transform fault. D) at the surface of sediment layers, far from spreading centers. 15. The Moho is located between the A) lithosphere and the asthenosphere. B) crust and the mantle. C) mantle and the outer core. D) inner and outer cores. 16. Phosphorites are A) pelagic hydrogenous sediment. B) volcanic. C) lithogenous sediment. D) pelagic biogenous sediment. E) pelagic ooze 17. Ocean basins become deeper moving away from ridges due to A) decreasing thickness of the lithosphere B) increasing density of oceanic basalts C) increases in sediment accumulation D) polar wandering E) thermal contraction 18. Salts in the ocean are derived from the following sources except: A) chemical weathering B) dissolved materials in river water C) erosion of the continents D) the formation of calcium carbonate shells E) volcanic activity 19. The deepest portion of the lithosphere is formed from A) oceanic basalt. B) terrestrial granite. C) a combination of basalt and granite. D) mantle material. E) the Moho. 20. Vine & Matthews determined that new ocean floor was produced at ocean ridges by examining A) apparent polar wandering. B) fossils in marine sediments C) glacial debris at various locations D) the location of ancient coral reefs E) the magnetic pattern of the seafloor

4 Part II. Fill in the blank/best word choice. Fill in the blank with what you think is the best answer to complete the sentence. 3 points each. 21. Less dense continents float above the more dense ocean basins because of. 22. If a chemical is very abundant in the ocean and has a low rate of delivery to the ocean from land sources, it will have a residence time in the ocean and will become part of the seafloor sediments. 23. A rapid change in salinity with depth is called a, while a rapid change in density with depth is called a. 24. Sediment distributions in the ocean are controlled by the balance of, destruction, and. 25. In a box model of phosphorous content in the ocean, the flux out of the box (as sediment, for example), must be if riverine inputs are the sole source of phosphorous to the ocean, and are equal to 1,000 kg/day. Part III. Short Answer. Provide the best answer to each question in a few words (not an essay), or using a diagram. 5 points each. 26. How many atmospheres have existed on the planet Earth? What was the same or different about them?

5 27. Draw a typical profile for temperature, salinity, and phosphorous in the ocean, indicating on your drawing which line represents each. Provide appropriate units for the axes. Indicate the halocline on your plot. 28. You are given a sediment core of unknown origin. At the top (surface of the seawater/sediment interface), there is a layer of red clay approximately 2 mm thick. Under that layer you find a mixture of some clay, but mostly diatom frustules and organic material, 5 cm thick. Under that layer there is a layer of almost pure calcium carbonate for another 10 cm, and finally, there is basalt under that layer. What can you determine about where the core was collected and the past history of the plate movement from these sediments? 29. How are the alignments and age distribution patterns of the Emperor Seamount and Hawaiian island chains potentially explained by hot spots? Why is there a dog leg in the chain? 30. You are house-sitting for your friend, who has a 50 gallon saltwater aquarium. After raiding the refrigerator, you walk into the living room and realize the tank is leaking! Being a good scientist you determine the leak is dripping at 0.5 gallons/hour. You put a garden hose in the top of the aquarium

6 to keep the tank from emptying while you transfer the fish. Based on this scenario, (1) draw a box model of the situation; (2) how fast should the hose flow to keep the system in steady state? (3) what would the residence time of the salt in the tank be, assuming your garden hose has zero salinity?

7 Essay Question (20 points): Answer ONE of the questions. You will be graded on completeness, organization, and content, and your ability to synthesize the various points we have covered in class. Note: essay implies structure and complete sentences, not a list of facts. Full credit will be given for an essay that attempts to integrate material from the lectures, readings, and discussions, with appropriate examples and justification. Partial credit will be given for less thorough answers. Points will be deducted for errors in content. 1) The Challenger Expedition is often considered to be the beginning of modern oceanography, but most people are more familiar with the voyage of the HMS Beagle, with Charles Darwin. Explain why Darwin s expedition is not the beginning of oceanography, and why the Challenger Expedition is considered to have started the disciplines of geological, physical, chemical, and biological oceanography. 2) Much of oceanography has benefited from tremendous advantages in technology. Choosing one technique, measurement, or discipline, describe how it has changed from the past to the present. If you had unlimited resources, how would you improve it in the next 10 years? 3) Based on your readings from class, explain the prevailing theories for how life originated on this planet, and how this relates to the oceans. Based on your answer, explain what plate tectonics has to do with the evolution of life on the planet.