Contour lines are used on maps to represent areas of equal elevation above sea level. Typically, these lines indicate the shape of the land surface.

Understanding Contour Line Behavior

Under normal topographical conditions, contour lines represent distinct elevations. A single point on the ground cannot have multiple elevations simultaneously. Therefore, contour lines generally do not intersect or merge.

Condition for Contour Line Intersection

Overhanging Cliff Scenario

The specific condition where contour lines appear to intersect or merge on a map is an overhanging cliff.

• An overhanging cliff is a feature where the upper part of a slope extends horizontally beyond the lower part.
• In such cases, multiple elevations exist at the same horizontal location on the map. For instance, the top of the overhang and the ground directly below it might fall within the same map grid area.
• To represent this vertical stacking of terrain, contour lines corresponding to these different elevations are shown merging or intersecting on the 2D map projection.

Analysis of Other Options

• Hills: Contour lines form closed loops. Closer lines indicate steeper slopes, while wider spacing indicates gentler slopes. They do not intersect.
• Steep slope: Contour lines are close together, showing a rapid change in elevation over a short horizontal distance. However, they remain distinct and parallel, not intersecting.
• Uniform slope: Contour lines are spaced equally, indicating a consistent gradient. They do not intersect.

Therefore, the only condition among the options where contour lines intersect is an overhanging cliff.