Transcript Maps

Topographic Maps
Earth Science Presentation
Topography
► Topography
 The shape of a surface, including its relief and
the relative position of features.
Topography
► Relief
– refers to the difference in the
highest and lowest elevations on the map.
 An area with ‘low’ relief would be relatively flat,
 An area with ‘high’ relief would be more
rugged
LOW RELIEF
HIGH RELIEF
Topographic Maps
► Topographic
Map
 – a map that uses contour lines to show the
changes of elevation at Earth’s surface;
 - shows natural features such as lakes and
streams
 - shows cultural features such as cities, schools,
dams, etc.
Topographic Maps
► Contour
Lines
 A line on a map that connects points of equal
elevation.
 Elevation refers to height above or below sea
level.
Contour line
Index contour
Contour Interval = 20 feet
Topographic Maps
► Contour
Interval – C.I.
 The difference in elevation between two sideby-side contour lines.
1250
 1250 – 1200 = 50
 50 feet every 5 lines
 50/5 = 10 feet per line
 Contour Interval = 10 ft.
Topographic Maps
► Index
Contour
 Every 5th line is darker than the others.
 Indicates the elevation.
1250
 Helps determine the C.I.
Reading Contour Lines
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Which slope is steepest?
Reading Contour Lines
1250
The closer the contours are to each
other, the steeper the terrain.
Rules for Topo maps:
1. Contour lines close around hills
and basins or depressions.
MAP VIEW
CROSS SECTION
Rules for Topo maps:
1. Contour lines close around hills
and basins or depressions.
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1230
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Hachures – short lines at right
angles to the contour lines that
indicate depressions.
Elevations of hachured contour
lines are equal to the adjacent
non-hachured line.
Usually indicate sink holes,
quarries, or other areas of
subsidence.
Rules for Topo Maps:
2. Contour lines never cross.
► If
they did it would mean a spot would have
two elevations.
Rules for Topo Maps:
3. Contours form V’s that point
upstream when crossing creeks.
Contour lines V upstream and water flows downstream.
Maps
► Map
Legend
 Explanation of meaning of symbols used on a
map.