Name: _________________________ Class: __________ Date: _________
Topographic Maps
One of the best ways of studying a land region is with a topographic map. The United
States Geological survey prints topographic maps of all parts of the United States. These
maps have contour lines that show the different elevations, or relief of the land. Symbols
are used to show natural and man-made features. North is toward the top of the map.
The map has a scale that shows distances in miles, kilometers, and feet. Most of these
maps show elevation in feet.
Purpose: To be able to read and interpret a topographic map, calculate gradients, and
draw a profile for an area.
Part A: Introduction
Read the following short article on Understanding Contour Lines and note the rules to
follow to help you understand and use topographic maps. Answer the questions that
follow in complete sentences.
Using A Topographic Map
by Jim Riesterer . . . . . Edited by Scott Hughes, Dan Narsavage & Diana Boyack
http://geology.isu.edu/geostac/Field_Exercise/topomaps/topo_interp.htm
Tips for Understanding Contour Lines
When first looking at a topographic map, it may appear somewhat confusing and not very useful. There are
a few rules that topographic contours must obey, however, and once you understand these rules the map
becomes an extremely useful and easy to use tool.
The rules are as follows:
•
•
•
•
Every point on a contour line represents the exact same elevation (remember the glass inserted
into the mountain). As a result of this every contour line must eventually close on itself to form an
irregular circle (in other words, the line created by the intersection of the glass with the mountain
cannot simply disappear on the backside of the mountain). Contour lines on the edge of a map do
not appear to close on themselves because they run into the edge of the map, but if you got the
adjacent map you would find that, eventually, the contour will close on itself.
Contour lines can never cross one another. Each line represents a separate elevation, and you can’t
have two different elevations at the same point. The only exception to this rule is if you have an
overhanging cliff or cave where, if you drilled a hole straight down from the upper surface, you
would intersect the earth’s surface at two elevations at the same X,Y coordinate. In this relatively
rare case, the contour line representing the lower elevation is dashed. The only time two contour
lines may merge is if there is a vertical cliff (see figure).
Moving from one contour line to another always indicates a change in elevation. To determine if it
is a positive (uphill) or negative (downhill) change you must look at the index contours on either
side (see figure).
On a hill with a consistent slope, there are always four intermediate contours for every index
contour. If there are more than four index contours it means that there has been a change of slope
and one or more contour line has been duplicated. This is most common when going over the top
of a hill or across a valley (see figure).
•
•
•
The closer contour lines are to one another, the steeper the slope is in the real world. If the contour
lines are evenly spaced it is a constant slope, if they are not evenly spaced the slope changes.
A series of closed contours (the contours make a circle) represents a hill. If the closed contours are
hatchured it indicates a closed depression (see figure).
Contour lines crossing a stream valley will form a "V" shape pointing in the uphill (and upstream)
direction.
1. What shape do contour lines make?
2. Why can’t two contour lines cross or touch?
3. How are steep areas indicated on a topographic map?
4. When a contour line crosses a stream, what shape will it make and what does that
indicate?
Part B: Part B will familiarize you with the basic concepts of map reading and contour
lines. Use the Mt. Pisgah map to answer the following questions.
1.
Is this area mostly flat or hilly? ______________
2.
Find the highest point on the map. Give the elevation for that point __________
What does the triangle by that point represent? ___________________________
3.
Which side of Mount Pisgah is steepest? (give compass direction) ___________
Explain how the map shows this? ______________________________________
4.
What is the contour interval for this map? _____________________
5.
In what general compass direction does Michael Brook flow? _______________
Explain how the map shows this _______________________________________
6.
How far is it from Drew Seminary to Michael Brook traveling by road? ________
7.
Michael Brook flows into a flat area near Carmel. What is this place like? ______
8.
What are the small dots (squares) along the road? _________________________
9.
What is the highest possible elevation for the hilltop labeled “A”? ____________
What is the lowest possible elevation for the hilltop labeled “A”? _____________
10.
What does the line labeled “Penn Central” represent? ______________________
Part C: In Part C, you will use a topographic map to calculate the gradient between 2
points in an area. The gradient is how fast the elevation changes between 2 points. To
calculate gradient, use the equation:
G=
∆FV
d
Use the Eagle Bay Quadrangle map to find the gradients from the following points:
1.
C to D (use the exact elevations)
2.
A to B (B is an exact elevation; estimate point A)
3.
How can you tell very quickly where the steepest (highest) gradients are on a
map?
4.
How can you tell very quickly where the gentlest (lowest) gradients are on a
map?
Part D: Now you will use a real topographic map to answer the following questions
and to draw a profile between two points.
1.
The latitude and longitude on this map are written as 3 groups of numbers:
44º07’30”. To read this, the first set of numbers are the degrees, the second set
are minutes, and the last set are seconds.
Between what two latitudes does this map cover? ___________ & ____________
Between what two longitudes does this map cover? __________& ____________
2.
What is the name of the urban area on the map? ___________________
3.
Name 3 schools in the city. _______________ _____________ ______________
4.
What 2 main roads enter and leave the city? ____________ ___________
5.
What land feature lies southwest of Mercy Hospital? _______________
6.
In what compass direction does the river between Lake Madelein and Heavens
lake flow? __________
7.
What is the contour interval on this map? ________________
What is the highest possible elevation of the hilltop just north of the “K” in Buck?
___________
8.
What total distance would you travel in a kayak from the boat launch on
Rte. 3 (30) to Trombley landing (on the north part of the map)? ___________km.
9.
What part of the map has the flattest land? _________________
How can you tell? __________________________________________________
10.
Draw a profile between points A and B (blue line) on the graph that follows:
(be sure to plot a scale on the vertical axis using the contour interval of the map)