Part A: You will
answers the 6 questions below
Topographical Map Information:
Contour Intervals Since each contour line represents a
specific elevation, two different contour are separated by the same difference
in elevation (e.g. 20 ft or 100 ft.). This difference between contour lines is
called the contour interval. You can calculate the contour interval by
following these steps:
a. Take the difference in elevation between 2 bold lines.
b. Divide that difference by the number of contour lines
Imagine that the difference between two bold lines is 100
feet and there are five lines between them. What is the contour interval? If
you answered 20 feet, then you are correct (100 ft/5 lines = 20 ft between
lines). 100 ÷ 5 = 20 ft between lines.
The legend on the map also gives the contour interval.
Interpreting Contour Maps
How does a topographic map tell you about the terrain? Let’s
consider the following principles:
1. The spacing of
contour lines shows the slope of the land. Contour lines that are close
together indicate a steep slope. This is because the elevation changes quickly
in a small area. Contour lines that seem to touch indicate a very steep slope,
like a cliff. When contour lines are spaced far apart the slope is gentle. So
contour lines help us see the three-dimensional shape of the land.
Look at the topographic map of Stowe, Vermont (Figure
above). There is a steep hill rising just to the right of the city of Stowe.
You can tell this because the contour lines there are closely spaced. The
contour lines also show that the hill has a sharp rise of about 200 feet. Then
the slope becomes less steep toward the right.
2. Concentric circles indicate a hill. Figure below shows
another side of the topographic map of Stowe, Vermont. When contour lines form
closed loops, there is a hill. The smallest loops are the higher elevations on
the hill. The larger loops encircling the smaller loops are downhill. If you
look at the map, you can see Cady Hill in the lower left and another, smaller
hill in the upper right.
concentric circles indicate a depression. The hatch marks are short,
perpendicular lines inside the circle. The innermost hatched circle represents
the deepest part of the depression. The outer hatched circles represent higher
elevations (Figure below). Volcanoes
craters would be shown this way on a topographical map.
portions of contour lines indicate stream valleys. The “V“ shape of the contour
lines point uphill. There is a V shape because the stream channel passes
through the point of the V. The open end of the V represents the downstream
portion. A blue line indicates that there is water running through the valley.
If there is not a blue line the V pattern indicates which way water flows. In
Figure below, you can see examples of V-shaped markings. Try to find the direction
a stream flows.
The top of this drawing is a topographical map showing the
are illustrated at the bottom.
On this map, the vertical distance between each contour line
is 10 feet.
1. Which hill is
higher, hill A or hill B?
2. What do contour
lines that are close together mean? _____________
3. Which is
steeper, hill A or hill B_ _______________________
4. How many feet of
elevation are there between contour lines? _____________
5. How high is hill
A? ___________ Hill B? ____________
6. Are the contour
lines closer together on hill A or hill B? ____________________