Geology Reference
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major eruption. Compare it with Figure 5.5 in the map sec-
tion at the back of the topic, which depicts deposits from the
1980 eruptions.
17. a.
How closely do the predictions in Figure 5.11 match
the locations of actual mudflows or lahars in the southern
half of zone 1 at end of the following valleys (see Figure 5.5
and 5.6).
Muddy River
15.
List the predicted events for each flowage-hazard zone
shown in Figure 5.11.
Pine Creek
16. a.
Was a preferred direction predicted for events in flowage
zone 1?
Zone 2?
Zone 3?
Swift Creek.
b.
What eruption processes and products that occurred, if
any, were not included in the predictions?
FIGURE 5.6
The general area impacted by lahars (mudflows) from Mount St. Helens. (Scott, 1988)
FIGURE 5.7
Longitudinal profile (along the river channel) of the Columbia River bed before and after the 1980 eruption of Mount St.
Helens. Dark shaded area represents the thickness of sediment deposited as a result of the May 18, 1980, eruption (Schuster, 1981).
