Final answer:
Solid contour lines on a topographic map represent consistent elevations of the terrain, while dashed contour lines indicate depressions. The spacing of these lines shows how steep the terrain is, with closer lines meaning steeper slopes.
Step-by-step explanation:
The difference between solid contour lines and dashed contour lines on a topographic map is that solid lines represent the surface of the earth at a constant elevation, while dashed lines typically indicate a depression or a downward fold in the terrain. Contrary to the choices provided in the question, solid lines do not necessarily represent higher elevations and dashed lines do not exclusively indicate lower elevations or ridges. Instead, dashed or hachured lines are used to depict depressions, with the hachures pointing towards the lower area within the depression, which can be at any elevation. Contour lines that form closed circles with hachures indicate a depression, while closed circles without hachures represent a hill or mountain. The spacing between contour lines indicates the steepness of the terrain: closely spaced lines suggest a steep slope, while lines that are further apart suggest a gentle slope.