Topography shape of the earth’s surface

Contours Make it possible to measure the height of Mountains Depths of ocean bottoms Steepness of slopes

Contours Imaginary lines that connect points of equal elevation Above or below a reference point Sea level is base level or Zero feet elevation

contours Each contour is a line of equal elevation Therefore, contours NEVER cross They show the general shape of the terrain contours

contours Intermediate and supplementary contours Found in between the index contours Help show more details of the land surface shape

contours Very close Indicate steep slopes Spread apart Indicate gentle slopes

Contour interval Vertical space between adjacent contours Relatively flat area – contour interval is small ex. 10 ft Mountainous areas – contour interval is large ex. 100 ft Interval printed on the map in the margin

Contour interval The difference in elevation between one contour line and the next is ALWAYS the same on a given map This difference is the contour interval

Never just stop Contour lines never end in the middle of a map They either form a closed loop or run off the edge of the map

Index contours Wider Darker Are marked along the lines with an elevation number

Bathymetric contours Below water level May be blue or black dependent on location Show the shape of the land beneath the water Interval may vary on each map Explained in the margins

Depressions Use hatchured lines to show depression Contour interval remains the same

Rivers Contour lines point toward the source of a river. In the picture in the right, the river is flowing from top right to bottom left.

Series Different size maps 7.5 minute series 15 minute series

Series The minutes refer to latitude and longitude 7.5 minute means the map covers 7.5” of latitude and 7.5” of longitude 15 minute means the map covers 15” of latitude and 15” of longitude

Details The 7.5” map shows more detail The 15” map shows a larger area, therefore shows less detail