Geography Reference
In-Depth Information
Figure A.10
Contour lines refl ecting low relief (left) and high relief (right). The map at left is part of the
U.S.G.S. North Olmstead Quadrangle, Ohio; the map at right is part of the U.S.G.S. Matterhorn
Peak Quadrangle, California.
on such a contour line thus are at the same elevation. The
spacing between contour lines immediately reveals the
nature of the local topography (the natural land surface).
When the contour lines at a given interval (e.g., 100 feet)
are spaced closely together, the slope of the ground is
steep. When they are widely separated, the land surface
slopes gently. Of course contour lines cannot be found
in the real world, and neither can the lines drawn on the
weather maps in our daily newspaper. These lines connect
points of equal pressure (isobars) and temperature (iso-
therms) and show the development of weather systems.
Note that the letters iso (meaning “the same”) appear in
these terms. Invisible lines of this kind are collectively
known as isolines, lines of equal or constant value. These
are abstract constructions, but they can be of great value
in geographic research and representation.
Area symbols take many forms, and we will see some
of them on the maps in this topic. Area symbols are used
in various ways to represent distributions and magni-
tudes. Maps showing distributions (of such phenomena
as regionally dominant languages or religions in human
geography, and climates or soils in physical geography)
show the world, or parts of it, divided into areas shaded or
colored in contrasting hues. But be careful: those sharp
dividing lines are likely to be transition zones in the real
world, and a dominant language or religion does not
imply the exclusion of all others. So distribution maps,
and there are many in this topic, tend to be small-scale
generalizations of much more complex patterns than
they can reveal. Maps showing magnitudes also must be
read with care. Here the objective is to reveal how much
of a phenomenon prevails in one unit (e.g., country) on
the map, compared to others. The maps on population
in chapter 2 are examples of such maps. The important
cartographic decision has to do with color. Darker should
mean more, and lighter implies less. That is relatively
easily done when the dominant color is the same. But on
a multicolored map, the use of reds, greens, and yellows
can be confusing, and fi rst impressions may have to be
revised upon examination of the key.
Some students who are fi rst drawn to the discipline
of geography go on to become professional cartographers,
and their work is seen in atlases, newspapers, magazines,
books, websites, and many other venues.
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