Geology Reference
In-Depth Information
map of the area. Figure 8.29, in the maps section at the
back of the topic, shows avalanche paths near Aspen. You
must first measure the area of the starting zone in square
feet or meters and convert this measurement to hectares.
Outline your starting zone on the map of Aspen. Also out-
line the beginning and end of the runout zone. Show your
calculations.
7. What evidence would you look for in the field to deter-
mine whether debris fans, such as at the mouth of McFarlane
Creek, is related to stream deposition or avalanches?
8. The colored map of the Aspen area was published in 1972.
Did McFarlane Creek avalanches present a hazard to people
at that time? Explain your answer.
Runout zone length
9. Compare Figures 8.28 and 8.29 (the colored map). Identify
changes in human use of the land at the base of McFarlane
Creek that occurred between 1972 (the date of the original
base map used in compiling Figure 8.29) and 1987, the date
of the revised map in Figure 8.28.
5. a. How does the runout distance you calculated for the
McFarlane Creek runout zone compare with the length of
the runout zone shown on the map?
b. Do the results suggest any changes for the map?
10. How have changes in human use of the land at the base
of McFarlane Creek increased or decreased hazards from
avalanches since 1972?
6. Notice that the contours at the mouth of McFarlane Creek
bend away from the range front out into the valley. They rep-
resent a debris fan or alluvial fan. Are there other debris fans
along the valley of Roaring Fork that could be related to
avalanche activity? If so, where are they?
Alta, Utah
11. First, let's look at a typical small-avalanche site on the
Alta map (Figure 8.30). Carefully identify, in the general area
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