Oceanography Questions
Duxbury Chapter 3

  1. What is the concept that adding or removing a weight from the earth's crust causes it to depress or rebound?
    Continental drift.
    Isostasy.
    Plate tectonics.
    Rifting.
    Seafloor spreading.

  2. What name did Alfred Wegener give to his theory of horizontal crustal movements?
    Continental drift.
    Isostasy.
    Plate tectonics.
    Rifting.
    Seafloor spreading.

  3. What name did Wegener give to his proposed single supercontinent?
    Eurasia.
    Gondwanaland.
    Laurasia.
    Pangea.
    Panthalassa.

  4. What type(s) of evidence did Wegener use to support his theory?
    Geographic fit of the continents and features thereon.
    Distributions of fossil plants and animals.
    Distributions of modern plants and animals.
    Paleoclimatic oddities such as glacial till, coral reefs, and coal.
    All of the above.

  5. Why was Wegener's theory rejected by geophysicists of the 1920's?
    Lack of a mechanism for continents to plough through oceanic crust.
    The concentration of continents in the northern hemisphere.
    The earth was then thought to be too young for such movements.
    The presence of a continent directly over the south pole.
    Wegener was not a geologist by training and couldn't get his ideas heard.

  6. How did non-believers in Wegener's theory explain plant and animal distributions in the southern hemisphere?
    Dispersal by the will of God.
    Dispersal via northern continents.
    Dispersal via now-sunken land bridges.
    Dispersal via rafting on logs.

  7. What finally convinced geologists that the continents did move?
    Lystrosaurus in Antarctica.
    Paleomagnetism.
    Dinosaur distributions.
    The mid-Atlantic ridge.
    Mantle convection.

  8. Iron-rich minerals loose their magnetism when heated above what temperature?
    Blocking point.
    Boiling point.
    Breaking point.
    Curie point.
    Melting point.

  9. When a ship passes over seafloor that has a 'reverse' magnetic polarization, how does this effect the magnetic field reading?
    The magnetic field is directed east.
    The magnetic field is directed south.
    The magnetic field is directed west.
    The strength of the magnetic field is slightly stronger than usual.
    The strength of the magnetic field is slightly weaker than usual.

  10. What is the character of magnetic anomalies on the seafloor?
    They occur in stripes that parallel mid-ocean ridges and are offset along transform faults.
    They occur in stripes that run perpendicular to mid-ocean ridges and parallel transform faults.
    They occur in stripes that parallel continental margins and transform faults.
    They occur in stripes that run perpendicular to continental margins and parallel to transform faults.
    They occur in stripes that parallel transform faults and end at mid-oceanic ridges.

  11. What theory did magnetic anomalies on the seafloor give rise to?
    Continental drift.
    Isostasy.
    Plate tectonics.
    Rifting.
    Seafloor spreading.

  12. What is the current comprehensive theory of horizontal crustal movements?
    Continental drift.
    Isostasy.
    Plate tectonics.
    Rifting.
    Seafloor spreading.

  13. What is the age order of sea floor types (the crust underlying them) from oldest to youngest?
    Abyssal hills, abyssal plains, mid-ocean ridge, continental shelf.
    Abyssal plains, abyssal hills, mid-ocean ridge, continental shelf.
    Continental shelf, abyssal plains, abyssal hills, mid-ocean ridge.
    Mid-ocean ridge, abyssal hills, abyssal plains, continental shelf.
    Mid-ocean ridge, abyssal plains, abyssal hills, continental shelf.

  14. Which sea is an example of rifting forming an incipient ocean?
    Baltic Sea.
    Bering Sea.
    Black Sea.
    English Channel.
    Red Sea.

  15. Which sea is a remnant of a larger ocean that has closed up?
    Baltic Sea.
    Bering Sea.
    Black Sea.
    English Channel.
    Red Sea.

  16. How does plate tectonic theory explain the Ural Mountains separating Europe and Asia?
    Intraplate orogenesis in Eurasia.
    Eurasia is moving over a hot spot in the mantle.
    Incipient rifting apart of Europe and Asia.
    Ancient collision and suturing of Europe and Asia.
    The Urals are the one mountain chain that was better explained by older theories.

  17. What does plate tectonic theory predict about the distribution of volcanoes and earthquakes?
    They should be evenly distributed throughout the earth.
    They should occur primarily along plate boundaries.
    They should occur primarily in deep ocean basins.
    They should occur primarily on continents.
    They should only occur along continental margins.

  18. Match the geologic features with the type of plate boundaries they are associated with.
    Geologic feature Plate boundary type
    Andesitic volcanoes.
    Basaltic volcanoes.
    Continental collisions.
    Deep-focus earthquakes.
    Deep-sea trenches.
    Island arcs.
    Long linear scarps.
    Mid-ocean ridges.
    Normal faults.
    Reverse faults.
    Rift valleys.
    Strike-slip faults.
    Subduction zones.
    Convergent plate boundaries.
    Divergent plate boundaries.
    Transform plate boundaries.

  19. Match each mountain/island system with the kind of convergent plate boundary that formed it (if any).
    Mountain/island system Plate boundary type
    Aleutian Islands.
    Alps.
    Andes Mountains.
    Appalachian Mountains.
    Cascade Mountains.
    Hawaiian Islands.
    Himalaya Mountains.
    Mariana Islands.
    Ural Mountains.
    Continental crust colliding with continental crust.
    Continental crust colliding with oceanic crust.
    Oceanic crust colliding with oceanic crust.
    Not a case of plate convergence.

  20. What is the east coast of the United States an example of?
    Active continental margin.
    Passive continental margin.
    Convergent plate boundary.
    Divergent plate boundary.
    Transform plate boundary.

  21. What is the San Andreas Fault in southern California an example of?
    Active continental margin.
    Passive continental margin.
    Convergent plate boundary.
    Divergent plate boundary.
    Transform plate boundary.

  22. What happens when a piece of continent reaches an ocean-bound subduction zone?
    Subduction ceases.
    A decollement forms along a foredeep.
    The continent is subducted.
    Subduction switches to the other plate.
    An island chain is quickly formed.

  23. What has become accepted as the primary mechanism for seafloor spreading?
    Density differences in the crust.
    Gravitational and tidal forces.
    Mantle convection cells.
    The pole-fleeing force.
    Weight of seafloor sediments.

  24. How is oceanic crust forced back into the earth's mantle?
    It wants to float but is forced to curl as it cools.
    It wants to float but is forced under by colliding plates.
    It wants to sink because it is made of high density minerals.
    It wants to sink because it is cold and therefore dense.
    It wants to sink because of its high iron content.

  25. Which modern continents were derived from Gondwanaland?
    Africa, Antarctica, Australia, India, South America.
    Africa, Antarctica, Australia, North America, South America.
    Asia, Europe, India, North America, South America.
    Asia, Antarctica, Australia, Europe, South America.
    Asia, Antarctica, Australia, North America, South America.

  26. Which ocean basin is a remnant of the universal ocean Panthalassa?
    Arctic.
    Atlantic.
    Indian.
    Pacific.

  27. What is the typical thickness of oceanic crust?
    1 km.
    5 km.
    20 km.
    35 km.
    70 km.

  28. What is the typical thickness of continental crust?
    1 km.
    5 km.
    20 km.
    35 km.
    70 km.

  29. How thick can continental crust get in mountain belts?
    1 km.
    5 km.
    20 km.
    35 km.
    70 km.

  30. How old is the oldest oceanic crust?
    200 million years.
    500 million years.
    2 billion years.
    4 billion years.
    8 billion years.

  31. How old is the oldest continental crust?
    200 million years.
    500 million years.
    2 billion years.
    4 billion years.
    8 billion years.

  32. What is oceanic crust primarily composed of?
    Basalt and gabbro.
    Granite and gneiss.
    Limestone and dolostone.
    Peridotite.
    Sandstone and shale.

  33. What is continental crust primarily composed of?
    Basalt and gabbro.
    Granite and gneiss.
    Limestone and dolostone.
    Peridotite.
    Sandstone and shale.

  34. What conditions characterize a passive continental margin?
    Quiet sedimentation.
    Thrust faults and folds.
    Transform faults.
    Volcanoes and earthquakes.
    All of the above.

  35. What is the concept of a floating crust in gravitational balance?
    Equilibrium.
    Isostasy.
    Orogenesis.
    Rifting.
    Subduction.

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