How are depressions represented on a map?

Depressions on a map are represented by closed lines with tick marks that point toward low ground. This symbol indicates a lower area in the surrounding terrain, such as a basin or hollow. The tick marks, which are also known as "hachures," serve to visually indicate the downward slope of the land towards the depression, making it clear to the map reader that they are dealing with a decrease in elevation. This method of representation is crucial for land navigation, as it helps soldiers and navigators to identify potential obstacles or features in the landscape that may impact their route or tactical decisions.

The other options do not accurately describe how depressions are represented. Open circles with arrows typically denote features like craters or wells, broken lines may represent something entirely different like a trail or boundary, and solid lines with elevation numbers usually indicate contour lines that show specific elevations, rather than depressions.