Earth Science Vodcast Network ESVN

Topographic Maps

Topographic or Contour Maps Show surface features of the Earth - natural or man made Topography- size and shape of land Show elevation -height above sea level A top or aerial view

How is elevation shown on topographic maps? Contour lines are drawn connecting areas of equal elevation (isograms) Shape reveals land features Contour interval is the distance between contour lines

Contour Lines cont. Spacing of lines depends on RELIEF- the difference between the highest and lowest points Every 5 th line is made in bold print & is called an INDEX CONTOUR

How do I interpret spacing on a contour map ? Closely space lines mean the land is steep Widely spaced lines mean the land is flatter or more gently sloping

Valleys, Streams & Mountain Tops Contour lines make V’s when they form valleys or cross streams The V points uphill or upstream A closed loop or circle represents a mountaintop or ridge

How do contour lines show decreases in elevation? Contour lines drawn with short, perpendicular lines are called HACHURES They represent decreasing elevation The first hachure is equal in elevation to the closest regular contour line The next hachure represents a decrease in elevation equal to the contour interval

What do the following colors mean on a topographic map? See p 876 Blue- water Brown- contour line Green- vegetation Red- highways Black- constructed features

What is a Bench Mark? An exactly measured elevation ▲ followed by a number marks the spot

U.S.G.S. Maps-Quadrangles 15 minute 15 ’ lat/longitude 13 X 17.5 miles 1: inch on map equals 1 mile ____ area ____detail 7.5 minute 7.5 ’ lat/long 6.5 X 8.75 miles 1: One inch on the map equals 2000 feet ____area ____detail

U.S.G.S. Maps-Quadrangles 15 minute 15 ’ lat/longitude 13 X 17.5 miles 1: inch on map equals 1 mile _more_ area _less detail 7.5 minute 7.5 ’ lat/long 6.5 X 8.75 miles 1: One inch on the map equals 2000 feet _less_ area _more _detail