Earth Science
November 2, 2015
TOPIC IN REVIEW
Contour Maps
Contour maps show a top view of a landscape region, also known as
topography. The lines represent different elevations on the map, and every
point on a line is equal. The elevation change between the contour lines is
equal on the entire map, and is called the contour interval. Contour rules
need to be followed when labeling the elevation of each contour line. When
analyzing a topographic map, or contour map, the contour interval and scale
are necessary to determine the gradient of the land. Scales will be given at
the bottom of most maps, and the units will be labeled, usually in km or mi.
In order to determine the gradient of the area, the difference in elevation
Earth Science
Contour Maps
The picture above
shows an image of a
contour map in which
you are able to see the
elevation and the
contour lines as they
increase up each hill.
1
Earth Science
November 2, 2015
between two points must be determined and divided by the distance between these two points. An
example is listed below.
The diagram above
shows the steps
necessary to calculate
the gradient of a
region.
It is sometimes difficult to imagine what the land looks like from a side view,
therefore we create profiles which give an accurate depiction of the area.
When creating a profile, a line straight line between two points will be
analyzed. To create the profile, only the horizontal lines on the graph paper
will be used to plot the points. Using a scrap piece of paper, a point will be
created for each contour line that passes through the profile line, and labeled
with the proper elevation. This will be transferred to the graph paper, and
points will be placed at the proper elevation on the horizontal lines. The
distance between the points is important because it will create an accurate
depiction of the slope of the profile. An example is shown below. Notice that
the closer the points are together, the steeper the slope. Earth Science
Contour Maps
2
Earth Science
November 2, 2015
Contour lines that have hachure marks on them represent depressions, or areas where the land is
dipping down. The arrow is pointing at a depression on the map below. These are common at the
top of a volcano, or where the land has settled. The key concept to remember when labeling the
depression lines is
that the first hachure
line has the same
value as the solid line
outside of it. In other
words, the value
repeats itself anytime
a solid line is next to a
hachure line. The land
between the solid line
and the hachure line
actually goes up
slightly when looking
at a profile view.
Earth Science
Contour Maps
3