Final answer:
Closely spaced contour lines on a topographic map signify a steep elevation change, representing a rapid increase or decrease in elevation over a short distance.
Step-by-step explanation:
On a topographic map, closely spaced contour lines indicate a steep change in elevation. This is due to the principle that contour lines represent areas of equal elevation. When the spacing between these lines decreases, this represents a rapid change in elevation over a short horizontal distance, which is characteristic of steep terrain. For example, when looking at the topographical map of Devil's Tower in Wyoming, the closely spaced lines indicate that the terrain is very steep, which is confirmed by a perspective photo of the actual location. Additionally, when comparing the steepness of two slopes by examining contour lines, the area with closer contour lines would be the steeper slope, such as the comparison between line A and line B in the provided example.