Write a note on contour lines
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Answer:
Contour line, a line on a map representing an imaginary line on the land surface, all points of which are at the same elevation above a datum plane, usually mean sea level. ... The diagram illustrates how contour lines show relief by joining points of equal elevation.
There are 3 kinds of contour lines you’ll see on a map: intermediate, index, and supplementary.
1. Index lines are the thickest contour lines and are usually labeled with a number at one point along the line. This tells you the elevation above sea level.
2. Intermediate lines are the thinner, more common, lines between the index lines. They usually don't have a number label. Typically one index line occurs for every five intermediate lines.
3. Supplementary lines appear as dotted lines, indicating flatter terrain.
There are 10 rules of contour lines:-
Rule 1 - every point of a contour line has the same elevation.
Rule 2 - contour lines separate uphill from downhill.
Rule 3 - contour lines do not touch or cross each other except at a cliff.
Rule 4 - every 5th contour line is darker in color. This is an INDEX contour line.
Rule 5 - Contour lines are closer together in steep terrain and farther apart in flat areas.
Rule 6 - Contour lines close to form circles (or go off the map) AND the inside of the circle is the top of a HILL.
Rule 7 - Closed depressions have HACHURE marks on the downhilll side of a contour line.
Rule 8 - Contour lines create V-patterns when they cross a valley (or drainage). The tip of the V ALWAYS points uphill.
Rule 9 - Contour lines create V (or U) patterns when they cross a ridge. The tip or blunt end of the V or U at a ridge ALWAYS points downhill.
Rule 10 - Contour lines on opposite sides of a valley or ridge occur in pairs.