To understand what happens at the bottom of the ocean, it is important to know the "layout of the land" through the use of bathymetric charts, which are similar to topographic maps of surface land. This activity enables the student to:

1. Correctly interpret underwater landforms as indicated on bathymetric charts

2. Apply information from bathymetric charts to accurately create a profile of the ocean floor along a single cross-section

3. Explore how knowledge of ocean floor bathymetry assists researchers in the field, and in particular in the search for the Giant Squid

Curricular Connections: art, geography, science, math, critical thinking

Levels: upper elementary through high school

Vocabulary:

Lesson:

1. Hand out the diagram of the ocean bottom with identified sea floor features. Have students note the different types of landforms and design a description of each one in a running glossary. If time allows, have students design their own ocean bottom using worded descriptions that include the new terms. Then have classmates draw the ocean bottom using those descriptions.

2. Share topographic maps of mountainous regions. These can be found in local camping stores, nautical supply stores, Rand McNally Map Stores, surveying companies, and through the National Geographic Society, the American Camping Association, or local compass orienteering associations. Topographic maps are basically a bird's eye view of a region of land in which elevations are expressed with labeled contour lines. The path of the lines follow the contours of the slopes they represent.

   Example:

   

   Teaching Notes: Such drawings of the land are known as maps, but if the drawings are of the sea floor, they are known as charts. The 805 meters would be the highest point on land, but it would be the lowest point in the sea. If a straight line is drawn horizontally across the map above such that two of its points cross the two highest elevations, the profile of the land along that line looks approximately like this: If those two points are considered depth because the drawing is a chart of the sea floor, the profile would be a mirror image: Once students have bathymetry charts in hand, ask for volunteers to explain how the maps are to be interpreted.

   Suggested Questions:

   • What do the numbers indicate?

   • Why are some loops of contour lines smaller than others?

   • Why are the circles drawn in squiggles and curves as opposed to smooth circular lines?

   • How can we tell the location of hills, valleys, trenches, and mountains?

   • Find a steep slope. How do you know it's steep?

   • Find a gentle incline. How do you know it's a gentle incline?

   • Find a place that seems to be like steps. On what do you base this observation?

   • How might such a map help a hiker? A pilot? A fisherman? A research expedition? A swimmer?

3. Have students then use their "mind's eye" to move their perspective of the region of land represented on the topographic map from its top to its side. It may be helpful to ask them to imagine standing on the edge and looking across the landforms. Once the new perspective is achieved, ask them to consider what a straight cross-section might look like. To display what is meant by this, the teacher can first show the top of a heavily topped pizza, a full pie, or a clay formation, which is analogous to looking at the topographic map view. The teacher places the object flat on a table and slices it across its center. When one half is pulled away, a cross-section is revealed. The ups and downs (mountains and valleys) of this cross-section form a single-point profile of the topography of the pizza, pie, or clay formation.

   For students who need concrete examples, have them individually create a sample slope with surrounding valleys with clay, including the formations described above. Then have them slice their slope and valleys in half themselves.

4. Refer students back to their topographic maps. Ask them to draw a line (in pencil) across one section of the region. Then ask them to draw a topographic profile for a cross-section of the region along that line.

   The profiles must accurately reflect the elevation ratios as indicated by the numbers on the topographic maps. For instance, if the indicated height of one mountain on the topographic map is 9600' (as indicated in the smallest circle of the group), and a nearby smallest circle (another mountain in another group of circles) indicates a height of 4800', then the corresponding profiles of those same mountains should indicate the ratio of size difference, one mountain twice the height of the other. In addition, the profiles must approximate the width of the landforms as indicated by the contour of the circles on the topographic map.

   Accommodation:

   For students who sliced their own clay slopes and valleys as described in the previous step, have them tip their clay formation on edge, putting the newly cut cross-section flat on their drawing paper. Then trace the contours of the cross-section and remove the clay. A reverse profile is left behind, which can be traced from the other side of the drawing paper in order to set it in the right perspective, or students can work with the reverse image as it is. Ask students what this represents (looking at the profile from 180 degrees off the original profile or from North to South).

5. When students are finished, have them exchange topographic maps and profiles. Then ask them to compare their classmate's profiles to the landforms indicated with numbers and circles on the topographic map. The final step is to report back to the classmates on the extent to which the profile accurately portrays the land at that particular cross-section.

6. To ensure understanding of topographic map attributes, it may be beneficial for you to ask students to take height measurements of a particular region of the classroom, then draw a topographic map of that region. Architects follow this sort of procedure as well. They compare floor plans to views from different planes.

7. Provide students with the bathymetric chart of the Kaikoura Canyon off the coast of New Zealand, where the Giant Squid Expedition is taking place. Bathymetric charts are just like topographic maps, except instead of height, they indicate relative depths. Ask students to study the contour lines and numbers and try to imagine the landforms under the water. Have them focus in particular on relative heights, depths, widths, and extensions of land.

8. Now have students draw either a single-point bathymetric profile of the canyon (as done with the topographic map above), or a 3-D elevated angle view of the canyon. The elevated view is achieved by moving our imagined perspective from 90 degrees (straight above) to about 30 degrees off the table top, a lateral move of 60 degrees. From here, we can see perspective, depth, shadows, and details of the landforms. Students who draw such a portrayal of the ocean bathymetry would need to draw in perspective, using shading and angled contours. An example of this is shown here:
   

9. Suggested questions to ask once the drawings are complete:
   • How does such detailed knowledge of the underwater canyon contribute to the success of finding giant squid or for conducting research in general?

   • What special characteristics of the Kaikoura Canyon's bathymetry must be considered by Dr. Clyde Roper and his colleagues?

   • What would be the most effective search patterns for the automated underwater vehicles and why? …For the Johnson SeaLink? …For the Ropecam?

   • Does the bathymetry give us a hint as to why sperm whales thrive here? If so, what is it?

   • How does such a knowledge help the local shipping or fishing industry?

   • How do you think bathymetric charts are made for regions such as this where it is difficult to get direct access to large regions of it?

   • Can these charts help find caves or undercut cliffs?

Please note for the students that ocean floors, particularly those that lie along major fault lines (as does Kaikoura Canyon), often change. An ocean bathymetric chart is a rough guide of the ocean floor at one moment in time. In each visit to a region, researchers take care to "re-chart" the ocean floor through sonar soundings and eyewitness testimonies from local scientists, fishermen and residents before making their descent.