Asked by Cocoa

Must all topographic maps have a contour line that represents 0 m of elevation?

I'm not sure about this question, but I don't think you do need a line of 0 m because each contour line is exactly the same apart from each other, so you could just subtract that amount to get zero. Am I right?
Answered by Ms. Sue
That depends on the location you're mapping. The lowest point on the contour map is marked. It could be 0 if the lowest part of the map is at sea level, or it could be below 0, if part of the map is below sea level.

http://raider.muc.edu/~mcnaugma/Topographic%20Maps/contour.htm

Each contour line represents the height of a landform. If it's a map of a steep hill, the contour lines are close together. If it's a map of gentle hills, the contour lines are much farther apart.
Answered by Cocoa
thank you Ms. Sue. I had a very steep rock, and the lines were close together. I guess not every landform must have a 0m contour line then.