Post-Visit Activity

### Objective

Students will make a topographic map and gain a better understanding of the meaning of contour lines.

### Background

It's one thing to make a map of a city's streets. Streets translate fairly easily onto a two-dimensional map. But how do you put a three-dimensional feature, such as a mountain, on a two-dimensional map? The answer is a topographic mapping, which has contour lines at given intervals. These give a sense of topography after one learns to "see" mountains on these flat maps. Contour lines are drawn at equal intervals in elevation on a topographic map. Where elevation changes rapidly (i.e., on a steep slope) lines are drawn close together. Lines representing gradual changes in elevation over an area are spaced farther apart. A contour interval is the difference in elevation (usually expressed in feet) between adjacent contour lines on a topographic map.

### Materials

- Clay
- Butcher paper for tracing sheets
- Topographic map from local area (needed fro the extension activity)
- Marking pens
- Fishing line or dental floss for cutting clay

### Procedure

1. Ask students, as individuals or in teams, to use their clay and make a mountain. The mountain should be at least large enough to fill the palm of their hand.

2. Introduce the idea of maps and how we often need to represent three-dimensional things like mountains on two-dimensional, flat maps by using contour lines. Ask students to trace the base of their clay mountain on the tracing sheet. Then ask them to cut their mountain horizontally, one-half inch above the base. Have them set aside the part of the mountain below the cut.

3. Next have your students lay down the remainder of their mountains on the tracing sheet within the lines already drawn to trace this new base. Each team should them make another horizontal cut, half an inch up from the base of the mountain and trace that new base, repeating these steps until they run out of mountain. The lines for each new base will fall inside the prior base's perimeter. They should end up with a mountain cut into several horizontal bands, a mountain they can reassemble by stacking the horizontal bands on top of one another. You students now have topographic maps of their mountains. The contour interval is one-half inch.

4. Ask students what the topographic lines look like for steep slopes and why. Ask students what the topographic lines look like for gradual slopes and why.

5. Reverse the process by giving all the students a topographic map of an imaginary mountain you have drawn and ask them to build a clay model of the map. Have the students compare how closely their mountains match each other.

### Extension

1. Have students place their reassembled mountains on desks around the classroom. Each student then gets a topographic map that a different student made and attempts to match the real mountain with the topographic map.

2. Students select a mountain from a topographic map of a nearby location. They then build a clay model of the mountain based on the map. Students check their work by going to look at the real mountains.