Contour lines do not ever cross one another because each line represents a different elevation on a topographic map. However, contour lines may merge in the case of a vertical cliff.
A topographic map is used as a graphic representation of features that appear on the earth's surface. Some examples are:
- Hydrography: streams, rivers, swamps and lakes
- Vegetation: both wooded and cleared areas, vineyards and orchards
- Relief: valleys and mountains, slopes and depressions
This kind of map can be difficult to read at first glance. Once a person understands the symbols, however, it becomes more clear.
Contour lines are used to represent the relief features in a topographic map. In the rare case that the Earth's surface is intersected at two different points, such as a cave or overhang, the two contour lines that are at the same point are represented by dashes rather than intersecting.
Noting the patterns in the contour lines helps one to view the topographic forms they represent. For example, a hill is represented by a series of circular contours. The closer the contour lines are to each other, the steeper the hill. If the contour lines do not connect to make a circular shape for the hill, this is because the hill is located at the edge of the map, and only a portion of the topography is represented.