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Altitude and elevation
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The number next to the small black triangle on a flat map describes __________.
This map of the island of Corsica clearly shows what the outline of the coast looks like. Here are a couple of bays. Here, the coastline is fairly regular, and then here is a sharp peninsula pointing north. But the map is completely flat, and on Corsica there are plenty of high mountains. What can we do then, to illustrate the variations in the flat and mountainous areas, on flat map?
One way is to use different colours. Usually, green means lowland terrain with forests. The higher mountains are yellow and brown. The darker the colour, the higher the mountains. And these small black triangles mark where the summits are.
The numbers describe how high the summits are, their altitude. 1767. 1855. But 1855 what? This is relative to sea level.
The ocean’s waters spread out evenly over the world, and the ocean’s surface is the same distance from the centre of the earth, wherever you are. So, this summit is 1855 metres above sea level, m. a. s. l.
The altitude is 1855 metres above sea level. The highest summit on Corsica reaches 2706 metres above sea level. The highest summit in the world, Mount Everest in Nepal, has the altitude of 8848 metres above sea level. Here is a map of another mountain. It’s a confusing array of lines all over the map, and this is a way to describe elevation.
If we follow one of the lines, the height above sea level is the same along the line. This is a contour line. The next contour line marks another height above sea level. The difference in altitude between two contour lines is called the contour interval. If the first contour line is 1000 metres above sea level, and the next is 1010 metres above sea level, the contour interval is 10 metres.
The more contour lines we see on the map, the higher the elevation of the mountain. Where the contour lines are further apart, like here, the mountainside is less steep. But here, where the contour lines sit closer together, the slope is steeper. And the closer the contour lines are to each other, the steeper the mountainside. So if you want to get to the peak of the mountain, take a route where the contour lines are far apart.
Unless … you want extra excitement.