Contour lines that are heavier and begin at zero elevation are known as?

Contour lines that are heavier and begin at zero elevation are known as?

• A. Index Contour Lines
• B. Intermediate Contour Lines
• C. Supplementary Contour Lines
• D. Contour Lines

Answer: (A)

On a topographic map, elevation is shown by contour lines. The heavier, darker lines that carry an elevation label are called index contour lines. They act as reference points for reading the map, typically occurring at wider intervals (often every fifth contour) and often starting at sea level so elevations can be gauged relative to that baseline. The lighter lines between them are intermediate contours, which use the same elevation interval but aren’t labeled. Supplementary contour lines are dashed lines added for extra detail when needed. So the heavy lines that begin at zero elevation and are labeled are index contours.

On a topographic map, elevation is shown by contour lines. The heavier, darker lines that carry an elevation label are called index contour lines. They act as reference points for reading the map, typically occurring at wider intervals (often every fifth contour) and often starting at sea level so elevations can be gauged relative to that baseline. The lighter lines between them are intermediate contours, which use the same elevation interval but aren’t labeled. Supplementary contour lines are dashed lines added for extra detail when needed. So the heavy lines that begin at zero elevation and are labeled are index contours.