Lessons in Bathymetry Mapping

Why Would Anyone Give High School Seniors Playdough?

Bathymetric Map of the Area Around the Canary Islands

It should have been interesting, educational, and fun. It felt like a disaster. I will be looking forward to the student reflections on this activity to give me further guidance on the value of the lesson.

Yesterday's lesson was actually a two-day activity on bathymetric mapping and involved playdough. It was three classes of high school juniors and seniors making 3-D maps of the ocean floor with playdough. Day one, after a lecture, students were given salt and flour, and a recipe for self-hardening clay. Day two, students were given bathymetric maps and instructions on gridding the map, gridding a shoebox lid, and transferring the map into a 3-D form on the shoebox. It didn't quite go that way.

Modeling the Seafloor in 3-D - Procedure

1.       To begin, you will need a shoebox lid, some material to form your "seafloor" (clay, sand, play-dough, or a mix of sand and plaster), toothpicks with labels, a pencil, and ruler.  You will construct a model of a seafloor. It is recommended that you work in teams of two.

2.       Note ocean floor features on your assigned bathymetric map. Refer to textbook figures, your notes, and/or the accompanying figures as necessary.  You should identify the following:

a.                   A coastal ocean zone - the coastal ocean bottom should contain a minimum of the following items:

·         A flat abyssal plain.

·         An underwater seamount or guyot.

·         A continental shelf, break, slope, and rise.

·         A submarine canyon on the continental shelf.

b.                  An open water zone - the deep-water bottom should contain a minimum of the following items:

·                     A flat abyssal plain.

·                     An underwater seamount or guyot.

·                     A section of the mid-ocean ridge.

·                     A trench and island arc system.

c.                   You may also see features such as:

·                     ridge

·                     trench

·                     submarine volcano

·                     accretionary wedge

·                     subduction zone

·                     collision zone

·                     transform fault

·                     spreading plate boundary

3.       Classify and label these features and plate boundaries on the paper map first.You will label these on your 3-D map after it is constructed.

4.       Using a ruler and pencil, draw a grid over your paper copy of the bathymetric map.  Transfer the grid dimensions, scaling if necessary, to the inside of your shoe box lid.

5.       Construct your ocean floor model, to scale, using your grids as a guide.  Make it as close to the map as you can. Label the floor features on the toothpicks and stand them in the appropriate locations. Your 3-D map will need to dry for a couple of days.

Lessons Learned

• Problem: Few took the time to grid the map or box lid. Modification: Do not have materials to make the clay available until after preliminary mapping and gridding is checked.
• Problem: Huge mess of playdough; too much material used; clay not to specifications for molding and shaping. Modification: Pre-measure flour and salt, if possible. Have clay mixed at assigned stations. If students are to measure ingredients, emphasize the need for precision in measurements, otherwise the clay is sticky, goopy, or gummy and won't shape well.
• Problem: Sloppy and hasty construction. Modification: Illustrate how to mold the clay into the various forms. Encourage the use of tools for shaping.Turn the "criteria list" into a full rubric.Have students peer assess.
• Problem: Difficult to see depths on black & white maps. Solution: Have laminated color maps; use erasable marker for the grid; Alternatively, provide color maps if possible (wasn't able to due to no color printer); alternatively, provide a map that shows elevations.

Student Bathymetry 3-D Maps,
materials: self-hardening clay, shoe box lid,  toothpicks, labels

In case you are interested, the recipe for the self-hardening clay is: