Читать книгу Geography For Dummies - Jerry T. Mitchell - Страница 106

Contour lines connect points of equal elevation. In so doing, they convey the shape (hence, “contour”) of the land they depict. Near the top of Figure 5-3b is a thin line labeled “50,” which connects points that are 50 feet above sea level. Farther inland is a line labeled 100, which connects points that are 100 feet above sea level. Thus, a walk from the water’s edge to a point on the second line involves a 100-foot gain in elevation. These elevation line features are a major component of topographic maps published by the United States Geologic Survey.

One important feature of contour lines is also their ability to tell us about slope steepness. Contour lines very close together means a greater elevation change over less distance. In other words, in that place the slope would be steep.

Other maps have similar lines that connect equal data points using an isoline (iso means equal). Want to connect areas of equal temperature on a map instead of elevation? Using the same process, now you have an isotherm instead of a contour line. All maps that use isolines to connect features of the same value are called isopleth maps.