Lab 11 Volcanic Hazards (1)
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Geol 116 Fall 2023
Name Nicholas DeNobrega
Lab 11 Volcanic Hazards
Volcanoes present a wide range of different hazards as a result of the variation in magma composition
and eruptive style (Table 1 is a nice review). While most areas of the United States are not locations of
active volcanoes, the impacts of major eruptions can be widespread. In this lab we’ll look at hazards
associated with three different styles of volcanoes in the U.S.—Yellowstone, Kilauea, and Mt. Rainier—
to get a good sense of the types and distributions of hazards.
Table 1.
Relationships among magma composition, viscosity, volcano form, typical eruption products.
Yellowstone National Park
Most of Yellowstone National Park is a caldera, formed at the active end of the Snake River Hot Spot.
A
generalized geologic maps is shown in Figure 1.
The caldera has produced major eruptions about 2.0
million, 1.2 million, and 0.62 million years ago, with estimated volumes of material of 2500, 275, and
1000 cubic km, respectively.
The two biggest eruptions produced widespread ash falls (tephra),
extending across much of the western half of the country, as shown in Figure 2.
Since the 0.62 Ma
eruption, smaller rhyolite eruptions have occurred within and outside of the caldera itself.
Earthquakes
have been occurring under and adjacent to the caldera, some shallow enough to suggest that magma
may be moving toward the surface.
And certainly there is considerable heat being generated, as
evidenced by the famous geysers and hot springs of the park. Use the figures to answer the following
questions.
1.
Other than its world-famous geysers and hot springs (which are a local hazard due to the hot
water), what volcanic hazard(s) are likely to exist in the Old Faithful area (west-central part of the
park) due to renewed eruption?
What is the basis for your hazard analysis?
Figure 1.
Simplified geologic map of Yellowstone National Park.
Thin lines represent contacts between
different rock units; thick lines represent the locations of faults.
Squiggles cover lakes (Yellowstone
Lake in the large one in the center of the park).
2.
Are there different hazards that might exist at the Mammoth Hot Springs area on the north edge of
the map?
Explain.
3.
Which of the ash deposits (Figure 2) covers a larger area?
Were the wind directions at the time of
eruption the same or different?
Figure 2.
Ash distribution from Yellowstone eruptions.
Points show locations where the ash deposit
has been identified.
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4.
The Huckleberry Ridge ash represents an eruption that was 2.5 times the volume of the Lava Creek
event.
But the area depicted for the Huckleberry Ridge ash is not 2.5 times the area depicted for
the younger Lava Creek ash.
What eruption characteristics and/or post-eruption processes could
explain the difference in the areas covered by these ash deposits?
5.
Scientists expect that the Yellowstone caldera will erupt again in the not-too-distant future (at least
in geological time frame).
What would be the principal impacts of a future mega-eruption?
Hawaii—Kilauea Volcano
The Kilauea volcano on the “big island” of Hawai’i has been extremely active historically, and indeed
throughout the last thousand years (Figure 3).
Ongoing eruptions have been occurring since 1983—the
longest eruptive episode during recorded history.
The spring and early summer of 2018 saw a
significant increase in lava volume emitting from fissures in the East Rift Zone area (Figure 4).
These
eruptions destroyed more than 700 houses and other buildings.
Use the maps of Figures 3-6 to answer the following questions.
1.
Sketch on lined or graph paper a topographic profile from the city of Hilo through the summit of
Mauna Loa from the topographic map, Figure 5.
Based on the shape, is Mauna Loa a basaltic shield
volcano, an andesitic composite volcano, or a dacitic-rhyolitic caldera?
2.
What hazard would you expect at Hilo from an eruption of Mauna Loa?
Kilauea?
3.
How does the area affected by the 2018 lava flows (Figure 4) relate to the other historical flows at
Kilauea (Figure 6)? How does it compare to the longer-term history of flows from Kilauea (Figure 4)?
Figure 3.
Distribution of geologically recent flows, Hawai’I, from Mauna Loa and Kilauea volcanoes.
Figure 4.
Map of lava flows from Kilauea volcano in 2018.
Figure 5.
Simplified topographic map of the big island of Hawai’i.
Figure 6. Volcanic hazard zones in the Kilauea area.
Zones 1 and 2 are highest hazard, based on history
of eruptions.
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Mt. Rainier, Washington
Based in part on an exercise by Stephen Nielsen, Tulane University
In your work as an insurance company executive for Denyallclaims Insurance Co.
you have been
reassigned to head up the Tacoma, Washington office. Although Tacoma is located about 50 miles (80
km) from the volcanic mountain, Mount Rainier, other executives in Denyallclaims have assured you
that the volcano has not erupted for a long time and there is no risk associated with the volcano. In
fact, the current manager of the office has offered to sell you his home in the suburb of Puyallup,
Washington, for what seems to be a good price. You decide to check things out for yourself, and go to
the internet to search for hazards associated with Mt. Rainier; the US Geological Survey
(
www.usgs.gov
) web page will be a good place to start. The following are questions you (and your
professor) want answered.
a.
When was the last time Mt. Rainier had a major eruption?
b.
Are there any types of volcanic hazards associated with Mt. Rainier that could affect you
in the future if you were living in the area of Tacoma or its suburbs? If so, what types of hazards have
affected the Tacoma area in the past?
c.
Considering that the summit area of Mt. Rainier is covered to a large extent by glacial
ice, would residents of the Tacoma area be threatened in any way by a small eruption from the volcano
that only sent a few lava flows down the flanks, none reaching more than 1 km from the summit? If so,
why, and if not, why not?
d.
Among the things you should be able find is a hazards map for the area around Mount
Rainier. One version, which shows the path of some prehistoric volcanic deposits, is included as Figure
7. Figure 8 shows how the USGS has classified the hazard; you can find the original source here:
http://vulcan.wr.usgs.gov/Volcanoes/Rainier/Publications/FS065-97/FS065-97_map.pdf
. What hazards
exist in Puyallup where the Denyallclaims manager has offered to sell the house? How often do events
represented by this hazard occur?
e.
Find a site on the internet that discusses Puyallup, Washington (but don’t rely exclusively
on Wikipedia).
Describe the location of Puyallup in terms of its topography and location relative to
rivers, and discuss why this location could be particularly at risk
f.
What steps have been taken in Puyallup to reduce risk from volcanic hazards?
g.
How much warning would the residents of Puyallup have were a lahar to be caused by a
Mount Rainier eruption?
Figure 7.
Map of major prehistoric Mt. Rainier lahar deposits
Figure 8.
Lahar risk from Mt. Rainier based on ages and frequency of lahar deposits.
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