Contour lines — Geography, 11–13
Contour lines turn the height of real land into a pattern on a flat map. They help you picture hills, valleys and steep slopes without climbing them.
A map that shows height
A contour line joins places that are at the same height above sea level. The numbers on the lines tell you the height, while the spacing tells you about the slope: close lines mean steep ground and wide gaps mean a gentler slope.
Why draw invisible height?
A flat map cannot show a hill by making the paper rise. Surveyors therefore needed a compact way to record land height and plan routes, roads or buildings. Contour lines solve this by turning many height measurements into a pattern that can be read from above.
Reading a hill
A map has contour lines labelled 100 m, 110 m, 120 m and 130 m, with 10 m between each line. A path crosses the 100 m line, then the 110 m and 120 m lines, so it climbs 20 m. If the lines become closer together, the path is entering a steeper section.
The trap: close lines are not high
It is easy to think that close contour lines mean a very high place. They do not: they show how quickly height changes across a short distance. A low hill can have close lines on its steep side, while a high plateau can have widely spaced lines.
Planning across real land
Hikers use contour lines to choose a route that avoids a difficult climb. Engineers also study them before placing a road, railway or reservoir, because slope affects safety, cost and drainage. The map helps with planning, but it cannot replace checking the actual ground.
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