Salad Tray 3D Topographic Model
Purpose
The purpose of this activity is to introduce students to the concept of topography as
represented by contour lines on topographic maps and help students make a connection
between topographic contour maps and the shape of the surfaces they represent. This
activity is meant to help students visualize relief from contour lines on a topographic
map.
Objective
The object of this activity is to create a three-dimensional model of a landscape
represented by a topographic contour map.
CA State Science Standards (9-12)
Investigation and Experimentation Standard:
1.h. "Read and interpret topographic and geologic maps."
Time Needed
Approximately 45 min
Background Information
Topographic maps are 2-dimensional representations of a 3 dimensional surface.
Contour lines are used to show vertical elevation. Each contour line represents a line of
equal elevation on earth’s surface. Sea level is the zero elevation contour line. Contour
line basics: Contour lines do not cross but may converge at locations that are steeply
sloped. The farther apart the contour lines are spaced, the more gently sloped the
represented surface is (gradient). The elevation difference between two adjacent contour
lines is called the contour interval. Concentric contours represent hills. Contour lines
take a V-shape pointing upstream or uphill where they cross rivers or the lowest point in
a valley.
V-Shaped Contours
Saddle
Ridge
Hill
Valley
Key Terms
Elevation
Contour interval
Contour line
Gradient
Relief
Topography (Hill, Ridge, Valley)
Scale
Materials Needed
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6-8 clear plastic salad trays (restaurant take-out style) per model
Topographic map of a landform you want to model (an island, mountain, or
canyon will work best…something with enough topographic relief) sized
correctly to fit the salad tray (one photocopy per model)
Tape
Non-permanent/erasable colored markers (vis a vis or dry erase—Quartet brand
dry erase can be wiped off easily with a paper towel) or grease pencils (at least
one per model) NOTE: permanent markers can be used if you do not intend to
reuse the salad trays).
Paper towel (for fixing mistakes)
Activity
1. From the topographic map, choose a contour interval. The difference in elevation
between adjacent contour lines (contour interval) should always be the same.
You should choose a contour interval that includes 6-8 contour lines (one for each
salad tray).
2. On the topographic map, use a marker to darken the contour lines that you wish to
use in the model. These contour lines will be transferred one each to a salad tray.
3. Cut the map to fit the bottom of one of the salad trays. Tape the map in place on
the bottom of that salad tray. Call this salad tray the base.
4. Stack the next salad tray onto the base rotated one quarter or one half turn so that
it should fit snug and there is the most significant height increase possible.
5. Trace onto this salad tray the lowest elevation darkened contour line.
6. Stack another salad tray on top of the first and trace the next highest elevation
darkened contour line.
7. Continue stacking salad trays and tracing contour lines until each of the darkened
contour lines is traced onto one salad tray.
Questions
In order to help the students translate the relief of their model into a landscape, you can
ask them to:
1) Label on their model landscape features such as:
ridge
saddle
valley
steep slope
hill
gentle slope
And/Or
2) Write a paragraph describing the landscape using the key terms