Final answer:
Contour lines are the solid or dashed lines on a civil drawing that represent the earth's elevation, helping to show the topography on a flat map and indicate terrain steepness.
Step-by-step explanation:
The lines on a civil drawing that represent the elevation of the earth are called contour lines. These lines may be solid or dashed, and they follow paths across a shape to indicate the topography on a flat surface, like a civil or topographic map. Essentially, contour lines are used to depict surface features and elevations, they can give an illusion of three dimensions on a two-dimensional map. The closer the lines are to each other, the steeper the terrain. For example, on a topographical map, such as one of Devil's Tower in Wyoming, the closely spaced contour lines indicate very steep terrain, just as the tower itself is steep.These lines are crucial for understanding the geography of an area and are often used by various professions, such as geologists, civil engineers, and surveyors, to analyze the landscape for construction, environmental studies, and more. When one looks at a contour map, it's able to show them not only the flat geographical layout but also the elevation, which is vital for proper planning and construction.