Geology Reference
In-Depth Information
FIGURE 8.30
Topographic map of Alta area, Utah (Dromedary Peak, Utah, 7.5-minute quadrangle).
marked
A
(the gully west of the Flagstaff Mine, on the south-
east side of Flagstaff Mountain), a starting zone for an
avalanche that might travel down the gully. Also mark the
track and identify a runout zone. Determine the slope angle
for the track and calculate the length of the runout zone,
based on your data and using the formula given in Question 4.
(The formula may not really apply here, but it gives an
approximation.) Show your work.
12.
The Alta Guard Station and other buildings are shown
along the road. Are these buildings at risk for a small
avalanche? Explain.
13.
Now let's look at the risk of an unconfined avalanche on
the same map. From the east side of peak 10277, which is
north of Hellgate Spring and southwest of Flagstaff Moun-
tain, draw a line along the 10,000 ft contour for 1 mile east.
Refer to Figure 8.24 as a guide, and mark clearly on the map
about how far you think that the runout zone from an
unconfined avalanche with a mile-long starting zone might
have gone. Was the town of Alta at risk for this type of an
avalanche? Explain.
Slope
Runout zone length
Bibliography
Armstrong, B. R., and Williams, K., 1992,
The Avalanche topic:
Golden, Colorado, Fulcrum Publishing, 240 p.
Bovis, M. J., and Mears, A. I., 1976, Statistical prediction of
snow avalanche runout from terrain variables:
Arctic and
Alpine Research,
v. 8, no.l, p. 115-120.
Bryant, B., 1972,
Map showing avalanche areas in the Aspen
quadrangle, Pitkin County, Colorado:
U.S. Geological Survey
Map I-785-G.
Brabb, E. E., and Harrod, B. L. eds., 1989, Landslides:
Extent and economic significance.
Proceedings of the 28th
