Recognizing horizontal layers on a geologic map depends on the topography of the area. Suppose we have flat layers in a Kansas-like area (a very flat land surface) as in the three dimensional figure at left. The surface (the middle figure) would show only one color. The geologic map (at right) would have only one color and symbol. The contour lines would be far apart indicating very little slope. The circle with an "x" or "+" symbol is used to indicate horizontal layers.