Ocean Depths and Earth's Crust
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Questions and Answers

Which of the following statements accurately describe(s) the depth and height of Earth's surface as shown on the hypsographic curve? (Select all that apply)

  • The average height of land is greater than the average depth of the ocean.
  • The percentage of Earth's surface above sea level is 29.2%. (correct)
  • The average depth of the ocean is much greater than the average height of land. (correct)
  • More people have been to the top of the tallest mountain on Earth than have been to the bottom of the deepest trench. (correct)
  • Why is the average depth of the ocean much greater than the average height of land?

    Oceanic crust is more dense than continental crust.

    To which planet is NASA sending the spacecraft InSight to study crustal movements similar to earthquakes?

    Mars.

    Which of the following is an example of an active continental margin?

    <p>West coast of Chile</p> Signup and view all the answers

    What features are associated with a passive continental margin?

    <p>Flat coastal terrain</p> Signup and view all the answers

    What is turbidity?

    <p>Suspended sediment.</p> Signup and view all the answers

    What effect do turbidity currents have on the continental slope?

    <p>Turbidity currents are erosive to the continental slope and, as a result, carve out submarine canyons.</p> Signup and view all the answers

    The reason the deposit on the bottom forms the way it does is a result of __________.

    <p>settling velocity.</p> Signup and view all the answers

    What is the characteristic layering of an individual turbidity current deposit called?

    <p>Graded bedding.</p> Signup and view all the answers

    The measurement of ocean depth and seafloor topography is called __________.

    <p>Bathymetry.</p> Signup and view all the answers

    What method is most frequently used to investigate sediment and rock layers of the sea floor?

    <p>Sound waves (specifically seismic reflecting profiling).</p> Signup and view all the answers

    What is the water depth in meters if a ship's fathometer records an echo 7.4 seconds later, and the speed of sound in water is 1,500 m/second?

    <p>5,550 meters.</p> Signup and view all the answers

    Which of the following techniques can be used to map the sea floor? (Select all that apply)

    <p>Using satellites to measure the sea surface</p> Signup and view all the answers

    Of the following statements about mapping the ocean floor, which is/are true? (Select all that apply)

    <p>Only about 20% of the sea floor has been accurately mapped in detail.</p> Signup and view all the answers

    Satellites use microwave beams to measure sea level to an accuracy of how many centimeters?

    <p>Four centimeters.</p> Signup and view all the answers

    Multibeam SONAR systems have resolution limitations in deep water because beams of sound spread out with depth.

    <p>True</p> Signup and view all the answers

    Active continental margins are characterized by which of the following?

    <p>Deep-sea trenches.</p> Signup and view all the answers

    The correct order of seafloor features from the coast to the mid-ocean ridge is:

    <p>Shelf, slope, rise, abyssal plain.</p> Signup and view all the answers

    Which of the following statements about Earth's hypsographic curve is/are true? (Select all that apply)

    <p>The hypsographic curve shows that a majority of the exposed land is below 1 kilometer in elevation.</p> Signup and view all the answers

    What percent of Earth's volcanic activity, each year, takes place on the seafloor?

    <p>85%.</p> Signup and view all the answers

    In comparison with other ocean basins, major sedimentary features such as continental rises and abyssal plains are relatively rare in the Pacific due to what reason?

    <p>Sediment is trapped within the trenches of the convergent plate boundaries ringing the Pacific.</p> Signup and view all the answers

    Few abyssal plains are located in the Pacific Ocean because turbidity currents only occur along passive continental margins.

    <p>False</p> Signup and view all the answers

    The largest single volcano on Earth, Tamu Massif, occurs in which of the following oceans?

    <p>Pacific Ocean.</p> Signup and view all the answers

    Volcanic peaks below sea level that rise more than 1 kilometer above the deep-ocean floor and have a flattened top are called ________.

    <p>Guyots.</p> Signup and view all the answers

    What type of sedimentary layering has the largest particles at the bottom and the smallest at the top?

    <p>Graded bedding.</p> Signup and view all the answers

    Volcanic peaks on the deep-ocean floor with conical tops are called:

    <p>Seamounts.</p> Signup and view all the answers

    Volcanic features on the ocean floor that are less than 1,000 meters tall are called:

    <p>Abyssal hills or seaknolls.</p> Signup and view all the answers

    Older lithosphere is destroyed in association with:

    <p>Deep-sea trenches.</p> Signup and view all the answers

    The island of Java is an example of a volcanic island associated with volcanic activity at a ________.

    <p>Island arc.</p> Signup and view all the answers

    Which of the following feature(s) is/are associated with the mid-ocean ridge? (Select all that apply)

    <p>Basalt volcanism and pillow lavas</p> Signup and view all the answers

    Study Notes

    Earth's Surface Depth and Height

    • 29.2% of Earth's surface is above sea level.
    • More individuals have climbed the tallest mountain than explored the deepest trench.
    • Average ocean depth significantly exceeds the average land height.

    Oceanic and Continental Crust

    • Oceanic crust is denser than continental crust, contributing to greater ocean depths.

    NASA InSight Mission

    • NASA's InSight spacecraft is studying crustal movements on Mars related to earthquakes.

    Continental Margins

    • Active continental margins are exemplified by the U.S. west coast and Chile's west coast.
    • Passive continental margins showcase features like continental rises and flat coastal terrain.

    Turbidity Currents

    • Demonstrated using a large jar of water mixed with sediment.
    • Turbidity refers to suspended sediment in water.
    • Erosion from turbidity currents carves submarine canyons into continental slopes.
    • Settling velocity determines deposit formation on the ocean floor.
    • Graded bedding characterizes turbidity current deposits.

    Seafloor Mapping and Techniques

    • Bathymetry measures ocean depth and seafloor topography.
    • Multi-beam sonar maps the seafloor within a 60 km strip.
    • Precision-depth recorders use high-frequency sound waves for depth measurement.
    • Hypsographic curves plot depth/elevation frequency.
    • Seismic reflection profiles explore the layered ocean structure.
    • Satellite measurements aid in mapping the seafloor due to surface reflection of underwater features.

    Sediment and Ocean Floor Features

    • Sediment layers and features in the ocean floor originate mainly from plate tectonic processes.
    • Abyssal plains are flat depositional surfaces extending from continental rises.
    • Seamounts are volcanic peaks on the deep ocean floor.

    Ocean Trenches

    • Older lithosphere is destroyed at deep-sea trenches, usually found near the Pacific Ocean.
    • Most ocean trenches associate with subduction zones, exhibiting narrow or absent continental shelves.

    Vicinity of the Pacific Ocean

    • The Pacific Ring of Fire contains most of Earth’s active volcanoes and earthquakes due to its tectonic features.
    • The Tamu Massif is the largest underwater volcano located in the Pacific Ocean.

    Hydrothermal Vents and Coastal Features

    • Transform faults run perpendicular to mid-ocean ridges and influence ocean floor features.
    • White smokers are hydrothermal vents formed in water temperatures from 30°C to 350°C.
    • Abyssal hills or seaknolls arise from volcanism and are less than 1,000 meters tall.

    Miscellaneous Facts

    • 85% of Earth's annual volcanic activity occurs underwater.
    • Graded bedding describes sediment layering with larger particles at the bottom.
    • The percentage of oceanic floor depths beyond 4,000 meters is significant according to the hypsographic curve.
    • The Pacific Ocean features relatively few abyssal plains compared to other ocean basins due to sediment trapping.

    Conclusion on Ocean Characteristics

    • All true oceanic islands are volcanic in origin.
    • The mid-ocean ridges are represented in the shallowest part of the hypsographic curve.

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    Description

    Explore the fascinating differences in Earth's surface depth and height, as well as the characteristics of oceanic and continental crusts. Learn about the dynamics of turbidity currents and their impact on submarine canyons. Discover how NASA's InSight mission is expanding our understanding of crustal movements beyond Earth.

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