6. Divisions
• Like time and temperature, latitude
and longitude are divided into
degrees, minutes, and seconds.
• For example:
N88º30’45” = 88 degrees (out of
90) north of the equator; plus 30/60
minutes, and 45/60 seconds north
beyond that.
7. Declination
True North= North on a map
Magnetic North= North on your
compass
The difference between the MAGNETIC
NORTH and TRUE NORTH is called the
MAGNETIC DECLINATION.
12. TOPO MAPS
• A topographic map is a two
dimensional representation of three
dimensional space.
• Utilizes contour lines to show
elevation.
• Contour lines are lines of equal
elevation.
13. • Elevation is distance above sea
level.
• A contour line connects points of
the same elevation.
• If you walked around an entire
mountain staying on the same
contour line, you wouldn’t change
elevation.
14. Index contours
• If we wrote the elevation of every
contour line on that line, then our
map would be covered in numbers.
• Instead, we use index contour lines.
1. Usually darker lines
2. Have the elevation marked on them
18. Rules for Contour Lines
• Contour lines always close to
form an irregular circle, it’s just
that sometimes you can’t see
the complete thing.
• Contour lines will make a ‘v’ in
the upstream direction a of a
stream.
19. Contour Lines ‘V’ Upstream
Topography of Appalachian valley surrounding the Rapidan River, Va (from Google Maps - Terrain)
20. Rules Continued
• Lines always increase unless
indicated by hash marks. These
hash marks indicate a
depression.
• Page 150 and figures 9.4-9.7 in
your manual is a great resource
21.
22.
23.
24. Relief
• The difference in elevation
between two points.
Total Relief
• The difference in elevation
between the highest point and
the lowest point on a map.
26. Gradient
• The change in elevation from one
point to another is the slope of the
terrain. This is a measure of how
steep the slope is, and also known
as the gradient.
12
12
XX
YY
Run
Rise
Gradient
30. How to Measure a Bearing in Degrees
Mount Saint Helens USGS Quadrangle
BUTTE
CAMP
DOME
N
S
EW
45°
Bearing Measurement
Quadrant Method = S 45°
W
Azimuthal = 225°
40. B.A. Digital perspective view derived from USGS Digital Elevation Model (DEM) of Mount St. Helens as seen
from the northwest prior to the catastrophic eruption of May 18, 1980. Created with Geographic
Information Systems (GIS).
41. B. Digital perspective view derived from USGS DEM of Mount St. Helens following the catastrophic
eruption of May 18, 1980. The 1980-86 lava dome has begun growing in the center of the crater.
42. C. Light Detection And Ranging (LIDAR)-derived digital perspective view of the volcano on September 22,
2003, one year before the start of its latest eruption. The 1980-86 lava dome and Crater Glacier
occupy the crater.
43. D. Digital perspective view derived from both LIDAR DEM and DEM constructed by photogrammetric
techniques, showing new lava dome, 1980-86 dome, and advancing Crater Glacier on July 5, 2007.
56. Mt. Saint Helens Resources
A Volcano Rekindled: The Renewed Eruption of Mount St. Helens, 2004–2006
http://pubs.usgs.gov/pp/1750/
Rebuilding Mount St. Helens
http://pubs.usgs.gov/sim/2006/2928/
A New Perspective on Mount St. Helens—Dramatic Landform Change and Associated Hazards at the Most Active
Volcano in the Cascade Range
http://pubs.usgs.gov/sim/3008/
Historic Digital Elevation Models (DEMs)
http://ned.usgs.gov/Ned/historic.asp
USGS Fact Sheet: Mount St. Helens – From the 1980 Eruption to 2000
http://pubs.usgs.gov/fs/2000/fs036-00/
Geologic Map of the Sasquatch Steps Area, North Flank of Mount St. Helens, Washington
http://geopubs.wr.usgs.gov/i-map/i2463/
360 ° Panoramic View of Mount St. Helens Crater
http://www.panoramas.dk/fullscreen6/f34-Mt-St-Helens.html
Teacher’s Corner – Mt. Saint Helens National Volcanic Monument
http://www.fs.fed.us/gpnf/mshnvm/education/teachers-corner/library/nasa-aster-series.shtml
Mount St. Helens National Volcanic Monument
http://www.fs.fed.us/gpnf/mshnvm/
57. Today’s Lab
• Construct a topographic map of the Egyptian
Pyramid of the Pharaoh Khafre
• Learn to read and navigate using topographic
maps
• Create a topographic profile
• Examine the topographic map of Mt. St. Helens
• Learn about volcanic deformation and evolution
of Mt. Saint Helens from digital topographic data