Top O' the Land
||edHelper's suggested reading level:
||grades 9 to 10
||Flesch-Kincaid grade level:
||closed-loop, isograms, reliefs, periodically, topography, perpendicular, human-made, cartographers, sunken, suburban, contour, reading, interval, urban, relatively, landform
||United States Geological Survey, United States
Print Top O' the Land
Top O' the Land
By Trista L. Pollard
1 If the surface of our planet was mostly flat, do you think scientists would develop only one type of map? We'll never know because the Earth is not close to resembling a flat sphere. Add a few landforms and a few man-made structures and you get the reason cartographers have developed topographic maps. Scientists need models that not only display the shape and size of a landform, but also display the elevation of a landform or structure. Topography focuses on the sizes, shapes, and elevations of landforms within a specific area. Similar for other types of maps, cartographers use information compiled in field surveys and from aerial pictures to design topographic maps. Scientists developed these maps which show natural land forms (mountains, rivers, hills, etc.) and human-made land forms (buildings, dams, roads, etc.).
2 Just like road maps and physical maps, topographic maps have their own special language. When scientists refer to a land feature's height, they don't say, "Gee that's a tall mountain!" Instead they describe the height of a landform as elevation. Elevation is the distance of a landform or structure above sea level. Scientists measure elevation by choosing a point halfway between the highest tide level of the ocean and the lowest ocean tide level. This is also referred to as the mean sea level (as in average, not mad), which has an elevation of zero. Scientists measure elevation from the mean sea level. Topographic maps are widely used by engineers, hikers, biologists, and other scientists because they show more detailed information about a land feature.
3 On topographic maps elevation is shown by using contour lines. At first glance, you will probably think there is just a bunch of "squiggly" lines on the map. Actually, these lines are isograms that connect points of equal elevation. The connecting points on the contour lines form the actual shape of the land. Contour lines also show the slope or steepness of an area and the area's relief. A relief is the difference between the highest points and lowest points of a region or area. When contour lines have a huge amount of space between them, then the change in the area's elevation is gradual. This also means that the area is considered to be level. When there is very little space between the contour lines, then there is a sharp increase in the area's elevation. You usually see lines like this at the base of mountains right before the land becomes very steep.
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