What are the three types of contour lines found on a map?

The three types of contour lines found on a map are index, primary, and supplementary.

Index contour lines are the thicker lines that are usually labeled with their elevation. They help provide a visual reference for understanding the terrain's elevation changes at a glance. Primary contour lines detail the elevation between these index lines, representing the same interval of elevation but without labels. Supplementary contours serve as additional guidelines and often represent intermediate elevations; they are generally lighter and help in depicting gradual changes in elevation.

This classification aids in reading topographical maps effectively, allowing users to understand the relief of the terrain, navigate landscapes, and plan routes based on elevation changes. Understanding these distinctions is essential for tasks such as planning hiking routes, understanding watershed areas, or conducting land navigational assessments.