Understanding Topographic Maps

Topographic Maps

• A topographic map is a type of map that shows elevation and is used by people like hikers who need to know the elevation of an area.
• Topographic maps show contour lines, which connect points of equal elevation, similar to the lines on a banana split sundae.
• Contour lines on a map are typically shown in a light brown color.

Contour Lines

• Contour lines show elevation, with each line representing a different elevation.
• Index contours display the exact elevation of one specific line.
• Index contours are usually labeled in two or three places on the map to avoid clutter.

Contour Rules

• Contour lines cannot cross, as this would mean a location has two different elevations, which is not possible.
• Contour lines form circles around hills or depressions.

Contour Intervals

• The contour interval is the distance between any two side-by-side lines.
• For example, a contour interval of 10 means that each line represents a 10-foot elevation change.

Hills and Depressions

• Contour lines close around hills and depressions, forming concentric circles.
• Lines get closer together on steep hills and farther apart on gentle slopes.

Hachures

• Hachures are small lines that show depressions or holes on a topographic map.
• Hachures resemble teeth in an open mouth and indicate a dip or bowl shape in the landscape.

Geologic Maps

• Geologic maps are similar to topographic maps but include additional information, such as the age and type of rocks.
• Geologic maps show topographic lines, ages, and types of rocks.
• Colors on a geologic map represent different types of rocks or ages of rocks, with different colors used for igneous, metamorphic, and marine-formed rocks.