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Chapter 3:
Mapping Earth’s Surface
Topography
The route of the Lewis and Clark
expedition crossed regions that differed
greatly in elevation, relief, and
landforms.
Types of Landforms
There are three main types of
landforms: plains, mountains, and
plateaus.
Types of Landforms
A large area of land where the
topography is made up of mainly one
type of landform is called a landform
region.
Comparing and Contrasting
As you read, compare and contrast the
characteristics of landforms by
completing a table like the one below.
Landform
Plain
Characteristics of Landforms
Relief
Elevation
Low
Low
Mountain
High
High
Plateau
High
Low
Maps and Globes
Maps and globes are drawn to scale and
use symbols to represent topography
and other features on Earth’s surface.
Scales and Ratios
A ratio compares two numbers by division. For
example, the scale of a map given as a ratio is
1:250,000. At this scale, the distance between two
points on the map measures
23.5 cm. How would you find the actual distance?
1. Write the scale as a fraction.
2. Write a proportion. Let d represent the distance
between the two points.
3. Write the cross products.
1 X d = 250,000 X 23.5 cm
d = 5,875,000 cm
Scales and Ratios
Practice Problem
A map’s scale is 1:25,000. If two points
are 4.7 cm apart on the map, how far
apart are they on the ground?
117,500 cm or 1.175 km; (1 X d =
25,000 X 4.7 cm) or (25,000 X 4.7 cm)
An Earth Reference System
Distances around circles are measured
in degrees.
An Earth Reference System
The equator and prime meridian divide
Earth’s surface into hemispheres.
Locating Points on Earth’s Surface
The lines of latitude and longitude form
a grid that can be used to find locations
anywhere on Earth.
Locating Points on Earth’s Surface
Every point on Earth’s surface has a
particular latitude and longitude.
Map Projections
A Mercator projection is based on a cylinder
with grid lines that has been flattened. On a
Mercator projection, lines of longitude are
parallel, so shapes near the poles are distorted.
Map Projections
An equal-area projection shows areas
correctly, but distorts some shapes
around its edges.
Map Projections
A conic projection is based on a cone that
covers part of Earth and is then rolled out flat.
A conic projection’s grid is formed from
straight lines of longitude and curved lines of
latitude.
Satellite Mapping
Google Earth
Mapping Earth’s Topography
Mapmakers use contour lines to
represent elevation, relief, and slope on
topographic maps.
Reading a Topographic Map
To read a topographic
map, you must familiarize
yourself with the map’s
scale and symbols and
interpret the map’s
contour lines.
Mapping Elevation Data
The map shows the
elevation data points
on which the contour
lines are based. Study
the map and the map
key, then answer the
questions.
Mapping Elevation Data
Reading Maps:
What is the contour
interval on this map?
Mapping Elevation Data
Reading Maps:
What color are the lowest
points on the map? What
range of elevations do
these points represent?
Yellow; points below
1,200 feet.
Mapping Elevation Data
Reading Maps:
What color are the highest
points on the map? What
range of elevations do
these points represent?
Red; 1,500 feet or
above.
Mapping Elevation Data
Applying
Concepts:
What is the elevation
of the contour line
labeled A?
1,300 feet
Mapping Elevation Data
Inferring:
Is the area between B
and C a ridge or a
valley? How can you
tell?
Valley; contour lines
curve uphill.
Mapping Elevation Data
Interpreting Data:
Describe how
elevation changes
along the trail from
point D to point C.
At point D, elevation is
above 1,500 feet. It then
decreases to about midway
along the trail where
elevation is less than 1,400
feet. Elevation then increases
again to point C, which is
above 1,500 feet.