3022
THE
CONTOUR
MODEL
To interpret the history of the earth's surface, maps must be constructed for
every area that is to be studied. The maps must contain accurate information
on the exact shape of the surface (topography). The understanding of these
topographic maps depends a great deal on the student's ability to understand
the concept of contour lines and what they indicate about the earth's surface.
The Contour Model Kit is designed to specifically illustrate what contour lines
are and what governs their shapes and patterns. The Contour Model itself is a
replica of Mount Capulin, a steep-sided volcano located in New Mexico.
Investigations - Time 60 Minutes
Specification of Materials
~ Transparent molded
plastic box containing
volcano.
~ Transparent plastic lid
~ Metric ruler
~ Marking pencil black
Additional materials
needed:
~ 3 Liters of water (in a
container suitable for
pouring)
~ Stereoscope (Hubbard
Product number 575),
optional
Part I: Three dimensional (raised relief) mapping_
Procedure
Provide one Contour Model Kit for each lob group. Explain that
each group is to construct a map of the plastic model provided in the
kit. The teacher may want to ask the students for ideas as to how to do
this. The students will probably suggest such things as different colors
to represent different elevations, or shading to represent the steepness
of the slope. Present the idea that lines can be used to show the shape
of the earth's surface. These are special lines which must always be at
right angels to the direction of the slope, and all points along each of
these lines are at the same elevation. To begin mapping, place the
clear plastic lid on top of the box containing the molded volcano.
Make marks one centimeter apart up the side of the box beginning at
the bottom. label the elevations: 0 centimeters, 1 centimeters, 2
centimeters, and so on. Then, carefully fill the container with water up
to the one centimeter mark.
Note: The outside dimensions of the model are intentionally smaller than the base of the clear plastic
box in order to facilitate drawing the 250' (1 centimeter) and 500' (2 centimeter) contours onto the
volcano model. It may be difficult to draw the 1 centimeter mark, but with a little creativity it can be
done. In the area around the volcano, try using the side of the marking pencil to draw instead of the
tip. Very slightly, heating the marking pencil, either with a match or a blow dryer set on warm, will
help the pencil write easily. Also, using food dyes, color the water blue. This will make the water line
easier fa see.
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As the contour is drawn around the model, follow its points of contact with the water exactly. When
this line has been drawn, sequentially raise the water level to each successive mark, drawing respective lines at each water level. (See figure 1).
Part II: Two dimensional (flat) mapping.
Procedure
When the volcano is completely submerged, empty the water from the box. Then cover the box with
its transparent lid. Carefvlly trace the lines from the model on the lid labeling each line with its eleva·
tion. (See figure 2).
To convert the contour lines into true altitude readings, the following scale should be used:
1 centimeter - 250 feet
Assume that the altitude at the bottom of the box (base of the volcano) is 6,280 feet above sea level.
Using the above scale, label each successive contour line on the plastic lid with the corred altitude.
The Contour Model can ba placed on on overhead proiector so that the process of mapping may be
demonstrated to the entire class at once.
Evaluation questions
Figure 2
Figure 1
1. Describe the general shape of the contour lines. They form irregular concentric circles around
the volcano.
2. What general statement can be made about the closeness of the contour lines and the steepness of
the slope' The closer the contour lines are spaced, the steeper is the slope of the land being
mapped.
3. Describe how the solidified lava flows affected the pattern of contour lines. They appear as a
series of nearly half-circles within the contour's larger circular pattem.
4. How would a steep valley down the side of the volcano change the contour pattern? As they
cross the valley the contour lines would all point sharply up-vaUey.
5. Would it be possible to distinguish a basin From a mountain on a toppgraphic mop? If the
basin is deep, the contour lines would show a decreasing elevation. Since each contour line on
a topographic map is not labeled, basins can also be distinguished by depression contours or
hachure marks.
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Part III: Comparison of model and map with actual photographs.
Procedure
As a reinforcement activity, students should compare their mops and the model fa the aerial photograph of Mount Capulin token from Wanless, Harold R" Aerial Stereo Photographs, p. 50, Hubbard
Sc::ientific, Inc. 1973. That photograph is reproduced on the adjoining poge. If a Hubbard Stereoscope (Product nu~ber 575) is available, the photograph can be viewed in a three-dimensional. 0$
well as a flat two-dimensional, aspect.
Evaluation questions
1. Where is the contour of the mountain steepest, and what indication of steepness do you hove
when comparing the model, the traced map, and the photograph? The steepest slope of the
model is along the sides of the crater as noted by a visual and tactile examination of the model,
by the closeness and lack of distance between the contour lines on the model and tracing, and
by the appearance of depth when viewing the photograph.
2. In what ways do working with a model and viewing a photograph help a person to understand
contour (topographic) maps? The three-dimensional model and stereophotograph are more
realistic representations of the mountain and relate more closely to one's experience, than
does the more abstract representation of elevation by contour lines. It is always beneficial to
be able to relate the concrete, realistic representation to the abstract representation.
Supplementary Materials
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•
•
•
•
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Stereo Photo Kit (Product number 30.42)
Map Reading ModellProduct number 625)
Map Reading Transparencies Sets I & II IProduct numbers 1055 & 1056)
Stereo Book of Contours (Product number 456)
Geo-landform Relief Map Set (Product Number .41 0)
Oceanography Transparencies Sets I & II (Product numbers 1035 & 1036)
Cleaning instructions
Use a moistened, nonabrasive wipe (tissue paper, co"on cloth, etc.l to clean the pencil markings off
the model. Abrasive material (like a paper towel) will scratch the surface of the model. Before
deaning the markings off the lid, place the lid of the model on a Aat level surface. The markings will
wash off easily. The model may be gently washed, from time to time, with warm soapy water and
dried with a nonabrasive wipe.
.
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Plate 50: MT. CAPULIN localion - New Mexico
Dale-June B, 1936
Scale - 1:20,000
Photographic Agency - USDA·SCS
University of Illinois Stereo No. -105
Map Reference - No topographic map
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Cinder cone, crater, and lava flows
Mt. Capulin is a steep·sided volcanic cone in northeastern New Mellico, formed of cinder ellploded at the time of eruption.
This lies on as steep a slope as is possible for loose material without sliding. A crater is in the center of the cone. A road
climbs to the lowest rim of the crater. Remnants of old lava flows which accumulated on much flatter surfaces are seen in the
upper left (stereo) and at the right where there is a long flow (nonstereo). This flow shows a series of wrInkles indicating
movement toward the upper right. This is typical of a fluid lava and is known by the Hawaiian name, pahoehoe. The source of
this lava may have been near the base of Mt. Capulin.
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