Geology 2
Interpreting Tectonic and Bathymetric Maps
Student Outcomes:
 Be able to understand and use basic map information, including scale, contour interval, legend, etc.
 Be able to recognize tectonic features, including mid-oceanic ridges, seamounts, trenches, and plate
boundaries on a bathymetric map
 Be able to identify the three types of tectonic plate boundaries using a bathymetric map
 Understand the processes occurring at the three types of plate boundaries
 Be able to determine the direction of tectonic plate motion by interpreting seafloor features on a bathymetric
map
 Create a cross-section using a bathymetric map
 Understand and use contour lines and contour intervals on a map
 Recognize and identify topographic features associated with the San Andreas and San Gregorio Faults
 Be able to identify seafloor features such as continental shelf, continental slope, continental rise, submarine
canyons, and seamounts on a bathymetric map.
 Develop a beginning understanding of how our world works so the student can make more accurate
assessments of presented information about our world and become responsible leaders and voters.
Materials:
 Map of “Measured and Estimated Seafloor Topography” from World Data Center (Note: This map is on
reserve at the MPC library and at the class website)
 Map of “Monterey Bay National Marine Sanctuary” from Monterey Bay Sanctuary Foundation, 1999.
 Wall map of the World
 Various other bathymetric maps and resources available during lab
 Plate tectonic map of the world
 Globe
Bathymetry Map Orientation
1) Using the bathymetric map “Measured and Estimated Seafloor Topography,” locate the colored depth scale
at the top. What color represents the deepest areas of the ocean?
2) What depth is represented by green? (Hint: Interpolate to the nearest 500 meters)
3) What is the average depth of the oceans abyssal plains?
4) How would you distinguish ocean floor that is 6,000 meters deep from ocean floor that is 7,000 meters
deep?
Atlantic Ocean
1) Using the world wall map or other lab resources, name at least one place where the Mid-Atlantic Ridge is
exposed above sea level.
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Geo 2 – Physical Geology Lab
Interpreting Tectonic and Bathymetric Maps
2) Using the bathymetric map “Measured and Estimated Seafloor Topography” locate the deep, broad abyssal
plains of the Atlantic Ocean. Where are there deeper areas of the Atlantic Ocean? (Hint: Remember the
deepest bathymetry is shown by a light purple color, not deep purple or blue.) Name or indicate the latitude
(using the scale on the right and left margins of the map) at least one of two clearly visible locations. What
is the tectonic setting of these deepest areas?
3) Is the east coast of South America at a plate boundary or in the middle of a plate? How do you know?
4) How does the shape of the Mid-Atlantic Ridge compare to the shape of the continental margins on either
side of the Atlantic Ocean? Why do you think this shape relationship exists?
Indian Ocean
1) Is Madagascar part of the African Plate? Why or why not?
2) Is Madagascar part of the African continent? Why? Or why not?
3) India and Australia are both part of the Indian Plate. Examining the portion of this plate northwest of
Australia, what features are found along the northeast boundary of the Indian Plate? What kind of tectonic
boundary is this?
4) What features are found along the southwest boundary of the Indian Plate? What kind of tectonic boundary
is this?
5) Considering your observations in answering the previous two questions, what direction do you think the
Indian plate moving? Explain your conclusion.
Pacific Ocean
1) What features do you find along the western boundaries of the Pacific Plate? What type of tectonic
boundary is this?
2) What features do you find along the southeastern boundary of the Pacific Plate? What type of tectonic
boundary is this?
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Geo 2 – Physical Geology Lab
Interpreting Tectonic and Bathymetric Maps
3) Considering your observations in answering the previous two questions, what direction do you think the
Pacific Plate is moving?
4) Locate the Hawaiian-Emperor Seamount Chain. Notice the bend in the chain. How might this bend have
formed? The age of the rocks at the bend is 43 million years old. Why do you think the seamounts become
progressively deeper to the north and west of Hawaii?
5) Where in the Pacific Ocean would you expect to find the oldest oceanic crust? Why?
6) Locate the Marshall Islands and the Louisville Ridge in the southwest Pacific on the map at the end of the
lab worksheet. Notice how the islands and the ridge seem to connect with one another. What do you think
happened to the missing islands in between? What feature do you see on the bathymetric map that supports
your guess?
7) Notice the chain of islands extending north from New Zealand. Why might you expect to find active
volcanoes on these islands? What kind of volcanoes would you expect them to be? Explain using what you
know about plate boundaries.
8) Using the bathymetric map, find the mid-ocean ridge in the southern Pacific Ocean at about 60 degrees
south. Notice how the mid-ocean ridge is composed of many offset sections. What type of plate motion
occurs in the linear areas between the offset ridges that are perpendicular to the ridges? (Hint: Consider the
plate motion that you know occurs at the mid-ocean ridges.)
Cross-sections
Using the bathymetric and topographic maps in lab, draw cross-sections along the lines indicated on the map at
the end of the worksheet. Use the lines A-B, C-D, and E-F provided on the next page to draw your crosssections. (Note that cross-section C-D goes right through Hawaii.) In your cross-sections, be sure to include
and label the following features, if present:
 Lithosphere
 Hot spots
 Asthenosphere
 Trenches
 Crust
 Convergent margins
 Approximate topography and bathymetry
 Divergent margins
 Sea level
 Transform margins
 Sites of active volcanism
 Mid-ocean ridges
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A___________________________________________________________________________________B
C___________________________________________________________________________________D
E___________________________________________________________________________________F
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Monterey Bay Area
Refer to the map of the Monterey Bay National Marine Sanctuary put out by the Monterey Bay Sanctuary
Foundation (1999) to answer the questions in this section.
1) Find the San Andreas Fault (SAF) on the map. You may need help from your instructor to do this.
a. In the northernmost part of the map, which bay marks the course of the SAF?
b. Near what famous landmark is the SAF located offshore rather than onshore?
c. Near what highway does the SAF cross the Pajaro River near Watsonville?
d. In the southern portion of the map, which highway follows the SAF most closely?
e. What two topographic features can one recognize that identify the location of the SAF on this map?
f. What kind of fault is the San Andreas Fault?
2) Note the light blue lines labeled with numbers in the offshore portion of the map. These lines are called
contour lines. A contour line is a line joining points of equal elevation, or, in this case, of equal depth. The
contour interval is the vertical distance between contour lines.
a. Referring to the map legend, in what unit is the depth recorded on this map?
b. What is the contour interval on this map close to shore?
c. What is the contour interval on this map far from shore?
3) The Monterey Bay National Marine Sanctuary map shows several seafloor features exceptionally well,
including examples of the continental shelf, continental slope, continental rise, submarine canyons, and
seamounts. Locate examples of each of these features on the big map in lab and label examples on the
Monterey Bay map in this handout.
4) Find the Monterey Fan in the southwestern region of the map. What type of material would you expect to
find here? How would it have gotten there? What could be the source?
5) How deep is the Monterey Canyon near the intersection with the Carmel Canyon in meters and in feet?
(One meter = 3.28 feet)
6) Find the reference map that shows the trace of the San Gregorio Fault south of San Francisco to the Santa
Lucia Range. Using the Marine Sanctuary map, describe two topographic features that are associated with
the trace of the San Gregorio Fault.
Congratulations on completing the Interpreting Tectonic and Bathymetric Map Lab! Remember the
bathymetric and the Marine Sanctuary maps are available for your use at the reserve desk at the library.
The bathymetric map is also available on the class website.
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Geo 2 – Physical Geology Lab
Interpreting Tectonic and Bathymetric Maps
Figures for Lab Worksheet
Pacific Ocean – questions 6 and 7
Cross-Sections Map
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Geo 2 – Physical Geology Lab
Interpreting Tectonic and Bathymetric Maps
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