Lab 3.1 – Seafloor Features

Fundamental concept: Identify plate tectonic boundaries and seafloor features on maps
Estimated time to complete: 15-20 minutes
Data skills preparation: Lab 1.2- Geography, Lab 1.3 – Latitude and longitude, Lab 2.2-Bathymetric charts
Materials needed: Computer

Tectonic plate interactions are directly related to many of the features that we find on the seafloor, such as volcanic seamounts, mid-ocean ridges, transform and fracture zones (Figure 3.1.1 right), and deep-sea trenches (Figure 3.1.1 left).

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Ocean map with divergent plate boundaries identified .
Diagram of subduction zone of Nazca plate subducting under the South American Plate resulting in a trench between the plates off the west coast of South America and the Andes mountains along the west coast of South America.
Figure 3.1.1 Mid-ocean ridges are locations where two tectonic plates are moving apart (Right) (Copyright: Benjamin R. Jordan, used with permission; Map imagery from the Global-Resolution Topography (GMRT) Synthesis, funded by the National Science Foundation (NSF).  Deep sea trenches form where subduction occurs (Left). (Image copyright: Benjamin R. Jordan, used with permission; Map imagery from Google Earth).

In the quick check orientation activities below, you are able to see the bathymetry of an area in the Western Pacific Ocean near Japan and an area in the northeastern region of the Pacific Ocean. You may retry the quick check questions as many times as you would like.  Use the background information provided to identify the various seafloor and geographic features in the images. You can also do web search if some terms are unfamiliar to you.

Orientation Questions

 


 

Now, using the above maps in the quick check questions, explore the data to see what observations you can make and answer the following questions.

  1. What is the range in elevation from the deepest seafloor to the highest mountains near Japan?
  2. What is the range in elevation from the deepest seafloor to the highest mountains near the Northwest U.S.?
  3. What is the distance used for the horizontal scale on the Japan map?
  4. What is the distance used for the horizontal scale on the map of the Pacific Northwest?

Interpretation Questions

  1. Describe any patterns or relationships between the topographic and seafloor features that you observe.
  2. Describe the type of plate tectonic boundaries that exist at these locations?
  3. Are there any differences between the tectonic boundary in Japan and the Northwest U.S.and if so, what are they?
  4. What are some possible explanations for why there is no obvious deep-sea trench near Oregon and Washington?

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