Lab: Ocean Bottom Topography
Background Information:
In certain places, the ocean bottom is almost flat and featureless whereas in other places the ocean
bottom consists of lofty ridges and volcanoes. Three distinct ocean-bottom zones are evident. The zone closest
to the shore features a very gentle slope extending seaward. From there the water depth increases much more
rapidly with distance. Finally, a relatively narrow zone is transitional from the steep slope of the previous zone
to the more-or-less flat ocean basin. The initial, gently sloping zone is the continental shelf; the second, steeply
sloping zone is the continental slope; and the third transition region is the continental rise.
The continental shelf, slope and rise together comprise the continental margin as shown to the right in
Figure 1. From a geological perspective, the continents do not end at the shore, but at the continental rise. At
its outer edge, the continental margin merges with the deep-sea floor or gives way to an oceanic trench. An
oceanic trench marks the convergent tectonic plate boundary where subduction of the oceanic plate is occurring.
Where there are trenches, the continental margin is abbreviated as shown to the left in figure 1.
Objectives:

Describe the features at the bottom of oceans

Construct a model of the ocean bottom

Distinguish between tectonically active and passive continental margins
Materials:

1 cup salt

2 cups flour

1 cup water

Cardboard box or shoebox

Food coloring
Procedure:

Each group draws out a plan for their ocean floor which includes a minimum of at least 10 ocean floor
features

After a plan is approved, see teacher for ingredients

Place water and food coloring in a bowl, add salt and mix.

Add flour and continue to mix to form dough.

Shape the ocean floor with the dough on the bottom of the box

Label the ocean features with toothpicks and flags
Terms to use in your model:

Abyssal plain

Continental shelf

Continental slope

Continental rise

Guyot






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Oceanic crust
Subduction zone
Trench
Mid-ocean range
Oceanic crust
Seamount
REFERENCES for post-lab questions:
Data Table 1:
Degrees West Longitude
70.0
70.2
70.4
70.6
70.8
71.0
71.2
71.4
71.6
71.8
72.0
72.2
72.4
72.6
72.8
73.0
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Elevation (m)
1945
2327
1193
-800
-1661
-3463
-4888
-7132
-5430
-4526
-3985
-4117
-4105
-4293
-3582
-4022
Names: ______________________________________ Date: ____________________________Pd._________
1. In the Figure 1, what is the unit for depth? ___________________________
2. In the Figure 1, what is the unit for distance? _________________________
3. Each small increment on the x-axis is _______ km and each small increment on the y-axis is _________
km.
4. What is the depth of the oceanic trench? __________________________________________.
5. The oceanic trench would be called a _______________if it were not underwater.
6. The oceanic ridge would be called a ________________ if it were not underwater.
7. Is the left side of figure 1 considered an active or passive continental margin? Why?
8. Is the right side of figure 1 considered an active or passive continental margin? Why?
9. The left side of figure 1 corresponds to which coast of the United States? _________________________
10. The right side of figure 1 corresponds to which coast of the United States? ________________________
11. Is the west coast an active or passive continental margin? _____________________________________
12. Is the east coast an active or passive continental margin? _____________________________________
13. What are two geological features found in ocean basins?
14. How can a tectonically active continental margin be distinguished from a tectonically passive
continental margin?
15. Where is new ocean floor created? How? Explain, using plate tectonics in your response.
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16. Describe the difference between a convergent and divergent boundary.
17. At which type of oceanic geological feature would you find a convergent boundary?
_____________________________
18. At which type of oceanic geological feature would you find a divergent boundary?
______________________________
19. At which type of boundary is seafloor created? __________________________________________
20. At which type of boundary is seafloor destroyed? ________________________________________
21. Describe one similarity between a guyot and a seamount.
22. Describe one difference between a guyot and a seamount.
23. Will a continental plate always subduct under an oceanic plate? Explain your reasoning.
24. Explain the differences between the Continental Drift Theory and the Plate Tectonics Theory.
25. The mid-ocean ridge of the Atlantic is called the _______________________________________ and
the mid-ocean ridge of the Pacific is called the ___________________________________________.
Analysis of Data: REFER TO DATA TABLE 1
1. The coast is located at ________W.
2. The greatest depth in the vertical profile is located at approximately _________W.
3. The difference in longitude between the coast and the deepest water location is ______
4. According to the graph, the depth of the deep-sea bottom in the open ocean west of the trench is
approximately ___________________________________ meters below sea level.
5. The deepest part of the trench is approximately ________________________________________meters
below the bottom of the open ocean west
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