Reading the Gap Between Blue Ridge Peaks

A flat map can describe a landscape that is anything but flat. In the Blue Ridge Mountains, part of the Appalachian Mountains, long ridges rise above narrow valleys. How can a map show those changes without standing up from the table? Consider an imaginary practice map of this region. Its heading, “Reading the Land,” introduces the clues that help readers picture the ground and compare two possible routes to a study point.

The first clue is elevation, the height of a location above sea level. A tree might be sixty feet tall, but that measurement is not the elevation of the ground beneath it. On this practice map, thin brown lines called contours connect places at equal elevation. Imagine tracing one line labeled 2,400 feet. Although the line bends across the page, every location along it has the same elevation.

The map key states, “Contour interval: 40 feet.” Here, interval means the vertical difference between neighboring contour lines, not the space between them on paper. Moving uphill from the 2,400-foot line, you would next cross lines representing 2,440 feet and 2,480 feet. Another map might use a different interval. Reading the key first prevents a reader from giving the lines the wrong values.

The spacing between contours provides another clue. Where the lines crowd together, the land rises a given amount over a short horizontal distance. That slope is steep. Widely spaced lines show the same rise spread over a longer distance, making a gentler slope. The word relief describes the difference between higher and lower elevations in an area. A landscape with large relief has a greater height difference than one with small relief.

Near the center of the practice map, closed contours surround two separate hilltops. Between them lies a saddle, a low place along the ridge connecting the higher ground. The name suggests a riding saddle: the land rises on two sides and is lower between them. A labeled point gives the saddle's elevation as 2,520 feet. A nearby caption reads, “The gap lies below the neighboring hilltops.”

Now compare the routes. Route A goes directly uphill across tightly packed contours. Route B curves toward the saddle across more widely spaced contours before reaching the study point. Both routes begin at 2,400 feet, end at 2,560 feet, and rise without going downhill. Each therefore has 160 feet of ascent, or upward travel. Yet Route B spreads that rise over a greater distance. It has a gentler gradient, meaning a less steep slope.

This comparison solves the map reader's problem: the shortest line on paper is not necessarily the gentlest climb. Contours, their interval, and their spacing work together to describe the landscape. They do not reveal every loose rock or muddy patch, so a map alone cannot establish actual trail conditions. They do, however, turn unfamiliar mountain shapes into information a reader can use.