For each statement or question, select the word or expression that best completes the statement or answers the question. ____ 1. Today, ships use a device called a precision depth recorder to A. collect samples of seafloor sediments B. determine the distance to the sea floor C. sample rocks from the sea floor D. make a videotape of the sea floor ____ 2. Which sea-floor feature is not commonly found at active continental margins? A. B. C. D. deep-sea trench continental rise continental slope continental shelf ____ 3. Satellites can obtain information about the sea floor because A. the satellite can "see" through seawater B. sea-floor sediments radiate infrared light C. the color of the surface water varies with sea-floor depth D. the sea surface level varies slightly with seafloor depth ____ 4. One method of obtaining a sample of sea-floor sediment with its layers preserved involves using a A. B. C. D. lead-weighted line grab sampler gravity corer sonar device ____ 5. The shelf edge is the boundary between the continental shelf and the A. B. C. D. shoreline continental slope deep-ocean trench continental rise ____ 6. Passive continental margins are characterized by the presence of A. B. C. D. coastal plains earthquake activity oceanic trenches rugged coastal mountains ____ 7. Suppose sound travels at an average rate of 1500 meters per second through seawater above a particular location. How deep is the ocean if a sound pulse takes 10 seconds to reach the bottom <i>and</i> return to a surface ship? A. 150 meters B. 300 meters C. 7500 meters D. 15,000 meters ____ 8. The portions of large submarine canyons that cut through the lower continental slope are thought to have been carved out by A. B. C. D. earthquakes changing sea level rivers turbidity currents ____ 9. The ultimate source of most of the material found on the surface of abyssal plains is A. sediments carried to the ocean by continental rivers B. shells settling from the ocean surface C. sediments eroded from abyssal hills D. sediments produced at mid-ocean ridges ____ 10. Abyssal hills are commonly found on the sea floor A. B. sea C. D. on the continental slope between continental rises and deeptrenches on the continental shelf next to oceanic ridge systems ____ 11. Deep-sea trenches occur at convergent plate boundaries where A. mid-ocean ridges are being created B. one tectonic plate is sinking beneath another C. one tectonic plate is sliding past another D. two tectonic plates are pulling apart from one another ____ 12. Where an oceanic plate descends beneath a continental plate, what features are common along the edge of the continent? A. B. C. D. earthquakes and guyots volcanoes and fracture zones earthquakes and volcanoes guyots and fracture zones ____ 13. Mid-ocean ridges are undersea mountain ranges where lithospheric plates are A. moving apart and new oceanic crust is being formed B. moving apart and old oceanic crust is being destroyed C. pushing together and old oceanic crust is being pushed up D. pushing together to form seamounts and guyots ____ 14. Segments of mid-ocean ridges are offset relative to each other by A. B. C. D. submarine canyons deep-sea trenches rift valleys fracture zones ____ 15. Sinking volcanic islands and developing coral reefs are related to the formation of A. B. C. D. manganese nodules atolls abyssal hills deep-sea trenches ____ 16. Sediments covering the ocean floor are A. of the same general composition everywhere B. all coated with a fine layer of rust that gives them a reddish color C. dissolved when they sink past the calcite compensation depth D. made up of a wide range of sizes that settle to the sea floor at different rates ____ 17. Sediments made from microscopic shells that settle to the bottom when the organisms that produced them die are called A. B. C. D. terrigenous sediments cosmogenous sediments biogenous sediments manganese nodules ____ 18. As rivers carry continental sediments to the ocean, the particles most likely to be deposited on the deepsea floor are A. muds and clays that can be carried great distances by currents B. metals that are commonly found in manganese nodules C. sands that are abundant along coastlines and beaches D. gravels that can sink quickly through the water ____ 19. As icebergs melt, they A. change the level of the calcite compensation depth B. change the amount of calcareous sediments produced in the water around them C. release sediments and pieces of rock that sink to the ocean floor D. add hydrogenous sediments to the ocean ____ 20. Sediments containing 75 percent of the ocean's siliceous sediment are found near? A. B. C. D. Greenland Iceland Australia Antarctica ____ 21. Manganese modules form A. as sediments settling through the water clump together B. at the surface of the sea floor C. where sediments are scraped off one lithospheric plate as it subducts beneath another D. in areas where sediments accumulate rapidly ____ 22. Scientists study the remains of marine organisms in seafloor sediments to learn about all of the following except A. the amount of water trapped in glaciers in the past B. the history of water temperature at the seafloor C. the climate of Earth in the past D. the composition of terrigenous sediments ____ 23. Surface currents in the ocean are primarily driven by A. B. C. D. winds waves temperature differences density differences ____ 24. Surface currents flowing away from the equator carry A. B. C. D. cool water upwelling water warm water downwelling water ____ 25. The winds that are most involved in forming ocean currents worldwide are the A. B. C. D. West Wind Drift and trade winds trade winds and westerlies westerlies and monsoons trade winds and monsoons ____ 26. In some regions there is a seasonal reversal in the direction of surface ocean currents due to a reversal in A. B. C. D. seasonal upwelling patterns seasons of the year seasonal wind direction seasonal temperature patterns ____ 27. Two examples of warm ocean currents are the A. Gulf Stream and the Kuroshio Current B. Kuroshio Current and the Canary Current C. Canary Current and the California Current. D. California Current and the Gulf Stream ____ 28. The British Isles and Iceland have warmer climates than they would otherwise because A. warm, moist air blows over the Labrador Current and warms it B. thick fogs provide insulation to hold heat in C. currents carry icebergs farther south before they melt D. the North Atlantic Drift carries warm water across the Atlantic ____ 29. Which of the following contains a core of Sargasso Sea water? A. cold-core rings of the Gulf Stream B. cold-core rings the Gulf Stream C. warm-core rings of the Gulf Stream D. warm-core rings the Gulf Stream on the continent side on the ocean side of on the continent side on the ocean side of ____ 30. What type of current flows in the opposite direction of wind-related currents? A. B. C. D. oppositional currents density currents countercurrents tidal currents ____ 31. Deep ocean currents are driven by A. B. C. D. tidal forces differences in density differences in oxygen content changes in conveyor belt circulation ____ 32. The circulation of ocean water is an efficient way to transport A. B. C. D. heat oxygen density evaporation ____ 33. Changes in density that lead to the formation of deep ocean density currents include all of the following except A. B. C. D. evaporation cooling freezing melting ____ 34. Turbidity current density results from water mixing with A. B. C. D. higher salinity water colder water cold-core rings sediment particles ____ 35. When seawater freezes, most of the salt A. is included in the ice, increasing its density B. is left behind, increasing the density of the remaining seawater C. is included in the ice, decreasing its density D. is left behind, decreasing the density of the remaining seawater ____ 36. The cause of the density current that flows over the Strait of Gibraltar into the Atlantic Ocean is A. B. C. D. cooling evaporation freezing mixing with sediment ____ 37. Upwelling is important to sea life because it A. B. C. D. cools the surface water brings nutrients to the surface water keeps ocean temperature uniform brings carbon dioxide to the surface ____ 38. Upwelling occurs along the western edges of continents, where surface water A. B. C. D. flows flows flows stops away from land toward land northward along the coastline flowing ____ 39. Major commercial fishing areas are usually located in areas A. where density currents form B. where seawater oxygen levels are high C. of persistent upwelling D. that experience frequent turbidity currents ____ 40. The gravitational pulls of the moon and sun cause Earth's tides. The sun's effect is about A. B. C. D. one quarter that of the moon's half that of the moon's equal to that of the moon's double that of the moon's ____ 41. Tides are highest when Earth is in line with A. B. C. D. the moon the sun both the sun and moon the tidal range ____ 42. The difference between high tide and low tide is most noticeable A. B. C. D. on the open ocean during neap tides when the moon is at apogee in long, narrow bays ____ 43. Which of the following is supplied to deep-sea life by density currents that form at the surface and then sink? A. B. C. D. oxygen food warmth salinity ____ 44. An area famous for its large tidal range is A. B. C. D. Lake Superior the Gulf of Mexico the Great Salt Lake the Bay of Fundy