What is the characteristic of contour lines in topographical maps?

Contour lines on topographical maps are a crucial element in representing the three-dimensional configuration of the terrain on a two-dimensional surface. The characteristic that is true about contour lines is that they never cross, except in rare cases where they indicate an overhang. This phenomenon occurs when a feature, such as a cliff or an undercut, creates a scenario where the elevation changes in such a way that two contour lines would seem to overlap.

The reason for this non-crossing property is that each contour line represents a specific elevation above a reference point, typically sea level. If contour lines were to cross, it would suggest that there is more than one elevation at the same horizontal position, which is not physically possible in the context of standard landforms. This characteristic allows anyone interpreting the map to understand the gradient and slope of the terrain effectively.

In contrast, the other choices describe misunderstandings of contour lines. They do not split randomly, nor do they solely represent particular types of slopes like convex ones. Furthermore, while contour lines can indicate flat terrain, they do not exclusively represent areas without elevation changes, as even flat areas can have contour lines that are spaced closely together to signify minor changes in elevation. Thus, the unique behavior of contour lines enhances the understanding