Put Your Face on the Map
By John Cowens

I was lying on the floor, listening to music, when my pet African Gray descended from his opened cage, climbed onto my face and settled on its highest point – my nose. Having a parrot on my nose made me realize that the elevations of a human face would make a great topographic map!

The contour interval of the above example is 100 meters. The example denotes a depression with hachures.

A favorite of hikers, "topo" (topographic) maps show the "relief," or heights, of hills, valleys and cliffs using contour lines. Contour lines are map lines that are drawn through all points with the same elevation.

The difference in elevation from one contour line to the next is called the "contour interval." On a map with a contour interval of 10 meters, the contour lines would be drawn only at elevations of zero meters, 10 meters, 20 meters, 30 meters and so on.

Rules for the ridges
The following rules will make it easy for your students to read topographic maps:

• Contour lines of one elevation never intersect a contour line of a different elevation. It's impossible for one point to have two different elevations.
• Closely-spaced contour lines represent steep slopes.



• Contour lines spaced far apart represent gentle slopes.


Students mark each contour line as the pan is filled with water one centimeter at a time.

• Contour lines that cross a valley are "v" shaped. If a stream flows through the valley, the "v" points upstream, or in the direction opposite to the flow of the stream.
• Contour lines form closed loops around hilltops or depressions. If the numbers marked on the contour lines increase toward the center, it's a hill. If the numbers decrease, it's a depression. Sometimes "hachures" are used to indicate a depression. Hachures are lines drawn perpendicular to the contour line; they point to the inside of the loop.

Making a topographic face map
Materials:

• plaster cast of a student's face, or a Halloween mask


• aluminum pan 11 3/4" x 9 3/8" x 4" (29.8 cm x 23.8 cm x 10.2 cm)


• transparent plastic or glass lid for the pan


• marking pen


• tracing paper


• plaster of Paris (one small box)


• acrylic paint (any color)

Three views of this student's face (from left to right): the plaster cast, the real thing and the topographic map.

Procedures:

1. Make a 3d plaster cast of a student's face from the ears to the tip of the nose, or use a plastic Halloween mask.
2. Paint the face one color
3. Set the painted cast in the center of the pan.
4. Mark a centimeter scale on the inside of the pan.
5. Pour water into the pan up to the one cm mark. Notice how the water forms a "shoreline" on the land form model (the face cast).
6. Put the cover on the pan. Trace the shoreline onto the cover. Look straight down at the shoreline as you trace.
7. Continue filling the pan with water, one cm at a time. Trace the new shoreline formed after each filling. When the land form is completely covered, you'll have a contour map of it.
8. Place tracing paper on the lid and trace the contour lines. Where are the steepest areas on the land form located? Where are the flatlands?

Extension
Have each student create a map of an isolated "Dream Island" that he or she would like to live on. The following should be included:

• Be able to produce your own food, shelter and materials for clothing.
• Include a cape, bay and lagoon that will protect against severe storms.
• The island should be no larger than 25 square miles and should include mountains, plains, rivers, a pier, jungle and any other features students would like to include.
• Draw contour lines at five-foot intervals.
• Students should give the name and the latitude and longitude coordinates of their islands.
• Students should create a scale to show distance (such as "one inch = two miles"), a contour line scale ("contour interval = five feet") and a map key with symbols for houses, bridges, depressions, lakes, roads, forests, etc.

John Cowens teaches sixth grade at Fleming Middle School in Grants Pass, OR.

January 2004, Vol.34, No.4