What information does an index contour line carry?

• A. Elevation value along the line
• B. Temperature data
• C. Land ownership
• D. Road width

Answer: (A)

Contour lines show points at the same elevation on a map. An index contour line is the bold, labeled line that carries the actual elevation value printed on it, so you can read the height directly from the map. This labeling lets you quickly gauge how high that line sits relative to sea level and estimate elevations elsewhere using the known contour interval between lines. Other kinds of information like temperature, land ownership, or road width come from different map layers and data, not from the elevation lines themselves.