Geology Reference
In-Depth Information
1
I
Exercise 4 • Volcanoes and Volcanic Hazards
57
1
1
FIGURE 4.3
The distribution of the Huckleberry Ridge and Lava Creek ash beds from Yellowstone, the Bishop ash bed from Long Val-
ley caldera, and Mount St.Helens ash of 1980 (modified from Lowenstern and others, 2005).
TABLE 4.3 Supervolcano Eruptions at Yellowstone and Long Valley
Supervolcano
Age of Eruption
Approximate Size of Eruption
Long-Term Recurrence Interval
Yellowstone
2.1 million years ago
2450 cubic km
£j*
Yellowstone
640,000 years ago
1000 cubic km
j i
625 cubic km
Long Valley
760,000 years ago
b. If Tambora had moderate global climatic impacts, what
impacts would a Yellowstone-size eruption have today?
6.
What geologic processes might have changed the distribu-
tion of ash since the time of eruption?
A2. Smaller-Scale Rhyolitic Eruptions
and Ongoing Geologic Hazards: Long Valley
and Yellowstone
7. Given their recurrence interval, do you think it is appro-
priate to worry about the eruption of a supervolcano? Why
or why not?
-J
-J
-J
After the cataclysmic eruptions described above, both
Long Valley and Yellowstone have had rhyolitic erup-
tions that have filled the calderas created by the big
eruptions. At Long Valley, the youngest eruptions may
have been only about 250 years ago. There were larger
eruptions about 600 years ago. Volcanism at Yellow-
stone is much older, with the youngest eruptions hav-
ing occurred about 70,000 years ago. (Christiansen and
others, 2007).
Several data sets, when combined, suggest the
interpretation that there is active magma beneath both
calderas. Long Valley and Yellowstone both have
8.
Figure 4.2 shows that the eruption of Tambora in 1815 pro-
duced between 100 and 1000 km
3
new material (it has been
estimated at about 150 km
3
of new material). This eruption
led to "the year without a summer" in some parts of the
United States.
a.
The eruption of Yellowstone about 640,000 years ago
was how many times larger than the eruption of Tambora?
La
