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Activity 2: Sea Floor Mapping
Extension Activity: Marine National Park in a Box
Background: In this activity the basic principles of measuring depth and constructing bathymetry charts are explored. A model of the sea floor is constructed in a shoe box and this is covered with a lid (representing the sea surface). Other students use a depth sounder (wooden skewer) to measure the depth of different points and use this information to construct a chart of the area surveyed. |
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Aim: To illustrate the principles of sea floor mapping and construction of navigational charts showing depth.
Materials:
- Shoe box or similar with a lid
- Graph paper
- Wooden skewer marked in 1 cm interval from the tip
- Bathymetry images of several Marine National Parks
- Quick drying plaster powder (cornice adhesive is an excellent fast drying and hard material)
- Containers for mixing plaster, sculpting, and cleaning up
Method:
Part A:
- Working in groups and using one of the bathymetric images as a guide to features found in Victoria’s Marine National Parks and Marine Sanctuaries construct a model of the sea floor on the bottom of a shoe box using plaster mixed with water. Try to include a variety of features including ridges, troughs, and flat areas.
- Glue a piece of graph paper to the top of the lid and cover the box.
- Exchange this with another group of students that have completed their park in a box model.
Part B:
- Using a wooden skewer punch holes through the lid of the box at each of the 1cm intersections.
- Using letters and numbers to label each point make a copy if the lid onto a separate piece of graph paper.
- Using the wooden skewer as a probe measure the “depth” of the various points and record these on the record sheet.
- When completed collected depth data draw lines to separate areas of different depth. Use different colours to shade these different depths.
Part C:
- By observing the pattern of depths predict what the shape of the park in the box may look like. Where do you think different features may be located?
- 0pen the box and compare your predictions with the model.
Discussion Questions:
- Did your predictions look like the model you were investigating? What differences and similarities did you notice?
- How could you get a more accurate picture of the sea floor using the skewer to measure depth?
- In Marine Habitat Mapping a multibeam sonar device sends out many signals from a boat that reflect off the sea floor and are recorded when returned to the boat. How would this give a measure of the depth of the water?
- Using multibeam sonar provides three dimensional images of the sea floor. What are some of the things that could influence the sending and receiving of multibeam signals from the boat of the sea floor?
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