Ocean Bottom Topography (a.k.a. Bathymetry)
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  • Website shows you the "ups and downs" of the floor of our global oceans
  • Discover that the margin between continents and the ocean varies a lot from place-to-place
  • Examine complex bathymetry on the continental margin

"Ocean bottom topography" is also known as bathymetry ("measurement of the depth of of large bodies of water")

On-line maps of "Measured and Estimated Seafloor Topography" are available from Scripps Institute of Oceanography, the National Oceanic & Atmospheric Administration, and Lamont Doherty Earth Observatory.

  • These digital bathymetric maps were created by combining ship depth soundings with high-resolution marine gravity data from Earth-orbiting satellites.
  • At this website, you can get a map of any part of the world's ocean by clicking on your area of interest.
  • The data maps are color-coded for easier interpretation.

At right (>>>) is a view of bathymetry from Nova Scotia to Cape Hatteras, North Carolina. The continental margin extends from the shoreline to the deep-ocean basin. The deep ocean is shown in blue and reaches about 5000 meters depth.

The continental margin includes:
  • The continental shelf
    • A gently sloping surface that extends from the coastline to a marked increase in offshore slope
  • The continental slope
    • A relatively steeply sloping surface found seaward of the shelf
  • The continental rise
    • A gently sloping surface at the base of the slope

Let's focus on one area on the continental margin, the Gulf of Maine (its "corners" are shown as white, above ^^^ ). A detailed view of Gulf of Maine bathymetry is shown in black-and-white below (VVV).

This a contour map. Its lines join points of equal depth.

  • Because black-and-white contour maps can be somewhat confusing to interpret, many oceanographers prefer to use color-coded maps to look at bathymetry data.
  • Compare the North Atlantic Ocean's bathymetry to other parts of the world
  • Examine the margin between North America and the deep ocean
  • The continental margin: how deep is it?
  1. Visit the "Measured and Estimated Seafloor Topography" website.
    • Look at the bathymetry data from the following areas:
      • Western Pacific Ocean (near the Philippines and Japan)
      • Western Indian Ocean (off the east coast of Africa and south of India)
      • North Atlantic Ocean (off the U.S. east coast)
    • Is the bathymetry of the North Atlantic more similar to that of the Western Pacific Ocean or Western Indian Ocean?
    • Would the floor of the North Atlantic's be better described as mostly an "innie" or an "outie"?
      • BONUS QUESTION: The bathymetric maps at this website were created by "combining ship depth soundings with high-resolution marine gravity data from Earth-orbiting satellites."
        • How can marine GRAVITY data help to determine the depth of the sea floor??!!
  2. Review the descriptions of the three zones within a typical continental margin.
  3. Look at the map below (VVV) that shows bathymetry off much of North America.
    • What varies more:
      • the DEPTH of the continental shelf or the WIDTH of the continental shelf?
    • Is the continental shelf off of New England's coast relatively narrow or wide?
      • Can you guess how having this type of continental shelf might affect currents and fish population?
    • Is the continental shelf closest to where you live relatively narrow or wide?
      • Can you guess how the width of "your" continental shelf might affect currents and fish population?
White line that parallels the North American coast shows the approximate width of the continental shelf.

4. Print a black-and-white contour map of Gulf of Maine bathymetry:

  • Click here to get the small version of the map.
  • Click here to get the large version of the map.
    • Using colors like those shown on this depth scale, trace over the CONTOUR LINES ONLY.
    • [NOTE: The maps do show depth below sea level although the contour lines are not marked as negative numbers.]
    • [HINT: Not all colors will be used!]
  • Compare the black-and-white contour map with your color-coded map.
  • Which map makes it easier to distinguish relative depths in the Gulf of Maine?
  • How would you describe Georges Bank: relatively shallow or relatively deep?
    • The color-coded scale for the global "Seafloor Topography" map was created to show bathymetry from sea level to greater than 7000 meters depth.
    • The depth scale provided for the Gulf of Maine (just above, ^^^) is altered from that map.
      • Can you name three or more changes between the two scales?
      • Why was it a good idea to use a different color scale for the Gulf of Maine bathymetry map?

5. Now that you've gotten familiar with global bathymetry data, which do you think is shows more variation -- or change -- from sea level:

  • Mt. Everest (highest land elevation) or the Mariana Trench (deepest ocean trench)?
  • Why did you choose this feature?
    • Click here to see a color-coded map with arrows that point to Mt. Everest and the Mariana Trench.
      • Does this help you to answer the question?
      • Why or why not? [If you need more help discovering which of these features has more variation from sea level, you may want to check an atlas or world almanac.]
  • bathymetry
  • color-coded
  • continental margin
  • continental rise
  • continental slope
  • contour map
  • gravity
  • topography
  • variation
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