Ocean and Continental Crust

Practice exam questions written by Timothy H. Heaton,
Professor of Earth Sciences, University of South Dakota

Click the circle by an answer with the mouse, then click on the Submit button to get a response. You will be told if your answer is correct or not and will be given some comments.

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

  2. Which seafloor province is cut by extensive submarine canyons?
    Abyssal hills.
    Abyssal plains.
    Continental rise.
    Continental shelf.
    Continental slope.

  3. Which seafloor province contains deep-sea fans?
    Abyssal hills.
    Abyssal plains.
    Continental rise.
    Continental shelf.
    Continental slope.

  4. Which seafloor province is underlain by continental crust?
    Abyssal hills.
    Abyssal plains.
    Continental rise.
    Continental shelf.
    Continental slope.

  5. 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.

  6. What type of deep sea sediments have graded bedding?
    Clays.
    Gypsum.
    Limestone.
    Sandstone.
    Turbidites.

  7. Where are the deepest places in the ocean?
    Abyssal hills.
    Abyssal plains.
    Continental rise.
    Continental slope.
    Trenches.

  8. Where are black smokers and deep-sea vent communities found?
    Continental shelves.
    Mid-ocean ridges.
    Seamounts.
    Transform faults.
    Trenches.

  9. What sequence of rocks make up ophiolite sequences of the ocean floor from top to bottom?
    Granite, andesite, basalt.
    Granite, diorite, gabbro.
    Pillow basalts, gabbro, sheeted dikes.
    Pillow basalts, sheeted dikes, gabbro.
    Sheeted dikes, pillow basalts, gabbro.

  10. What are flat-topped undersea mountains called?
    Atolls.
    Guyots.
    Rifts.
    Seamounts.
    Trenches.

  11. Where are coral reefs found?
    In polar waters.
    In tropical waters.
    Only in deep-sea trenches.
    Only around andesitic islands.
    Only around basaltic islands.

  12. Which sequence is thought to represent the evolution of coral reefs around volcanic islands?
    First barrier reefs, then fringing reefs, then atolls.
    First barrier reefs, then atolls, then fringing reefs.
    First fringing reefs, then barrier reefs, then atolls.
    First atolls, then fringing reefs, then barrier reefs.
    First atolls, then barrier reefs, then fringing reefs.

  13. Which seafloor sediment precipitates directly from seawater?
    Biogenous sediment.
    Exogenous sediment.
    Hydrogenous sediment.
    Terrigenous sediment.
    All of the above.

  14. Which seafloor sediment is derived from land?
    Biogenous sediment.
    Exogenous sediment.
    Hydrogenous sediment.
    Terrigenous sediment.
    All of the above.

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

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

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

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

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

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

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

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

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

  24. What is another term for mountain building?
    Equilibrium.
    Isostasy.
    Orogenesis.
    Rifting.
    Subduction.

  25. Where do accretionary wedges form?
    Above subduction zones.
    In deep ocean basins.
    In mountain tops.
    In rift valleys.
    On passive continental margins.

Please report any problems or errors to Dr. Heaton.