Name
CHAPTER 3
Class
Date
Models of the Earth
SECTION
3 Types of Maps
KEY IDEAS
As you read this section, keep these questions in mind:
• How are elevation and topography shown on a map?
• What are three types of information shown in
geologic maps?
• What are two uses of soil maps?
What Is a Topographic Map?
There are many different kinds of maps. Each kind of
map shows different information. One common kind of
map is a topographic map. A topographic map is a map
that shows the surface features, or topography, of an
area. Topographic maps show three main things:
• natural features, such as rivers and lakes
• features made by people, such as bridges
• elevation, or the height of an object above sea level
READING TOOLBOX
Ask Questions Read this
section silently. As you read,
write down questions that
you have about this section.
Discuss your questions in a
small group.
Look at the two figures below. The figure on the left
shows a picture of an island. The figure on the right
shows a topographic map of the same island.
X
715
00
7
LOOKING CLOSER
0
500 60
400
300
200
100
1. Apply Concepts About
how long is this island from
the southwest corner to the
northeast corner?
1 km
The topographic map on the right shows the features and elevation
of the picture on the left. An X marks the highest point on the map.
The picture of the island shows the island’s shape. A
regular map of the island could use a scale to show its
size. The topographic map shows the island’s topography,
in addition to its shape and size. In this way, a topographic map gives more detail than a picture or a regular
map.
READING CHECK
2. Compare How is a
topographic map different
from a regular map?
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Models of the Earth
Name
SECTION 3
Class
Date
Types of Maps continued
Type of Model
What It Shows
Shape
Critical Thinking
3. Infer Why is a contour
line a type of isogram?
Size
Picture
X
Regular map
X
X
Topographic map
X
X
Elevation
X
CONTOUR LINES
Topographic maps use contour lines to show elevation.
A contour line is an isogram that connects points with
the same elevation. Contour lines that are far apart show
a gradual change in elevation. Contour lines that are
close to each other show a steeper slope.
50 m
The distance between
contour lines shows how
steep or gentle a slope is.
LOOKING CLOSER
4. Identify Circle an area
on the map that has a steep
slope. Put a square around
an area that has a gentle
slope.
Critical Thinking
5. Apply Concepts A point
on a map is halfway between
the 50 m contour line and
the 60 m contour line. What
is the elevation of the point?
contour interval = 10 m
A contour interval is the difference in elevation
between two contour lines. For example, the map above
has a contour interval of 10 m. Therefore, the difference
in elevation between two contour lines is 10 m.
Some contour lines are drawn darker than others.
These darker lines are called index contours. They make
the map easier to read. In the map above, every fifth
contour line is an index contour.
You can estimate the elevation of a point on a map by
looking at the two contour lines near it. The elevation of
that point is between the elevations of the two contour
lines. For example, a point halfway between the 100 m
and 110 m contour lines has an elevation of about 105 m.
Some points on a topographic map are marked with an
×. A number is written next to the ×. That number is the
exact elevation of that point.
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Models of the Earth
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SECTION 3
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Types of Maps continued
RELIEF ON TOPOGRAPHIC MAPS
Relief is the difference between the highest elevation
and the lowest elevation on a topographic map. On some
maps, the relief can be as large as 100 m. On other maps,
it may be as small as 1 m.
OTHER SYMBOLS ON TOPOGRAPHIC MAPS
Most topographic maps use colors and symbols to
represent objects. For example, a map might have symbols to show roads, railroads, and buildings. These
symbols are generally black. Bodies of water are generally blue, and forests are generally green. Major highways
are red.
The shapes of contour lines can give you information
about the landforms on a map. For example, a contour
line may be shaped like a small, closed circle. That contour line represents either a hill or a very low area. A
contour line shaped like a V represents a valley. If there is
a river in the valley, the V will point upstream. It points in
the direction opposite that of the river’s flow.
50
6. Identify What color is
generally used to show water
on a topographic map?
Closed circle:
top of a hill
m
0m
10
V-shaped
Contour Line
READING CHECK
50 m
50
m
LOOKING CLOSER
contour interval = 10 m
7. Apply Concepts What is
the elevation of the top of
the mountain in the top right
corner of the map?
The shapes of contour lines give information about landforms.
What Is a Soil Map?
Earth scientists use soil maps to show the properties
of the soil in an area. People can use soil maps to understand how to use land most efficiently. They can also use
the maps to identify ways to conserve soil.
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Models of the Earth
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Types of Maps continued
SOIL SURVEYS
To create a soil map, cartographers do a soil survey of
the area. During the soil survey, they record information
about the types of soils in the area. They collect samples
of soil from many different places in the area. The figure
below shows an example of a soil map.
Soil maps help scientists
understand how to best
use the land in an area.
Talk About It
Investigate Use the Internet
or library to find a soil map
for your county or for another
area. Find out which areas on
the map are best for growing
different kinds of plants, such
as corn, wheat, or pine trees.
Share what you learn with a
partner or a small group.
What Are Geologic Maps?
READING CHECK
8. Describe How do
geologic maps show
different geologic units?
Geologic maps show the geologic features of Earth.
Most geologic maps show the types of rocks in an area.
They also show the locations of geologic structures.
Most geologic maps start with a base map. The base
map shows features such as mountains or roads. As
Earth scientists study an area, they learn about the different kinds of rocks and other landforms in the area. They
mark that information on the base map. They add color
and special symbols to represent different landforms.
Cartographers use different colors to represent the
geologic units on a geologic map. A geologic unit is a
layer of rock that is all the same age and type. Units that
are similar ages generally have similar colors.
Cartographers label each geologic unit with a set of
letters. The set contains one capital letter and one or
more lowercase letters. The capital letter stands for the
rock’s age. The lowercase letters stand for the type of
rock.
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Models of the Earth
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Types of Maps continued
CONTACT LINES
Geologic maps also contain symbols called contact
lines. A contact line is a place where two geologic units
meet. There are two main kinds of contact lines: depositional contacts and faults. Depositional contacts show
where one rock layer formed above another. Faults are
cracks where rocks move past each other.
LOOKING CLOSER
9. Identify The geologic
units on this map are
separated by black lines.
What are the black lines
called?
Each color on this map shows a different type and age of rock. Scientists can use
this geologic map to see which types of rocks are in this area.
What Are Some Other Types of Maps?
Topographic maps, geologic maps, and soil maps are
not the only kinds of maps Earth scientists use. Earth
scientists may use maps to show the movements of wind
and water. They may use maps to show where earthquakes and volcanoes are likely to happen.
Different scientists use maps in different ways. For
example, meteorologists use some maps to predict
weather events. These maps may show the amount of
precipitation that falls on different areas. They may also
show the location of high and low atmospheric pressure.
Meteorologists use these maps to predict weather and to
warn people about weather emergencies.
Some maps show where and how groundwater flows.
Structures and systems such as power plants, garbage
dumps, and new communities can pollute groundwater. Geologists can use groundwater maps to find the
best places to build such structures. Other maps help
geologists to study changes in Earth’s surface over
time. Geologists may use these maps to study changes
in topography, in the amounts of available natural
resources, and in climate.
READING CHECK
10. Explain Why is it
important for meteorologists
to share the information on
their maps with the public?
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Section 3 Review
SECTION VOCABULARY
contour line a line that connects points of equal
elevation on a map
elevation the height of an object above sea
level
relief the difference between the highest and
lowest elevations in a given area
topography the size and shape of the land
surface features of a region, including its relief
1. Explain A small topographic map contains the following contour lines (in meters):
40, 50, 60, 70, 80, 90. What is the relief of the map? What is the contour interval?
2. Infer How could a topographic map be useful for a hiker?
3. Apply Concepts An Earth scientist is studying the geologic history of an area. She
wants to know when different rock layers in the area formed. Which kind of map
should she use? Explain your answer.
4. Identify What are two ways people use soil maps?
5. Compare Complete the table below to compare topographic maps, geologic maps,
and soil maps.
Type of Map
What Colors Represent on the Map
Topographic map
black = roads and buildings; blue = water;
green = forest; red = major highways
What Lines Represent on the Map
different geologic units
places where different kinds of soil touch
6. Identify Give two examples of how people can use maps to help the environment.
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Models of the Earth