| How
do scientists predict volcanic eruptions?
[One way
is to monitor seismic activity around the volcano. The
first evidence of an impending eruption is usually a
series of seismic events or earthquakes. In order for
an eruption to occur, lava must rise from its formation
zone deep underground to near the surface. The lava
must literally push overlying rocks aside to rise through
them. The rocks are brittle and break as they are bent
and twisted, releasing seismic energy that we record
as earthquakes. By placing a number of seismic recorders
around a volcano, the movement of the new mass of rising
lava can be followed. (http://www.cotf.edu/ete/modules/volcanoes/vmonitor.html)]
What evacuation
procedures are currently in place in Washington State
and the Mt. Rainier area?
[According
to FEMA, most communities in the vicinity of Mt. Rainier
have plans in place. For example, the Orting school
district keeps the school buses at the school to evacuate
the flood plain where the schools are located given
enough warning.]
How do
the climates and weather around Mt. Pinatubo and Mt. Rainier
compare?
[Mt. Pinatubo
does not have an extensive glacier system like Mt Rainier.
Therefore, during an eruption of Mt. Rainier, the glacial
ice would melt quickly, causing larger and more devastating
lahars. Mt. Rainier's precipitation seems to be mostly
in the form of snowfall. The visitor's center (at 5,500
feet) averages 575 inches of snow. In the winter of
1971-72 it received a record 1,122 inches.]
Will seasonal
weather variations influence the effects of a major
eruption?
[Assuming
that Washington does not get as much water in as short
a time as do the Philippines during their rainy season.
Therefore, the physical destructive impact of an eruption
of Mt. Rainier would be more limited to the acute effects
of the immediate eruption. This is not to say that there
would be no long-term effect. I simply don't think that
the problem of lahars would pose a threat year after
year. I base this on what little I know of the Mt. St.
Helen's aftermath. To my knowledge, lahars did not become
a chronic problem.]
What will
happen to the glaciers on the top before and during
an eruption and where will the water go?
[As magma
builds, the ground water supply heats up, and snow and
ice may melt and cause increased water flow. I wonder
if this can be used to predict an eruption.]
What are
lahars, what are they composed of, and where will they
travel?
[LAHAR- A
flowing mixture of water - saturated rock debris that
forms on the slopes of a volcano, and moves downslope
under the force of gravity, sometimes referred to as
debris flow or mudflow. The term comes from Indonesia.
Lahars occurred at Mt. St. Helen's in 1980.]
What damage
did lahars cause in the Mt. Pinatubo area?
[From what
I have read, much of the destruction caused from Mt. Pinatubo was caused by lahars resulting from normally
heavy rainfall occurring over a four-year period. Mt.
St. Helen's in 1980 ejected .25 cubic miles of volcanic
material, but Mt. Pinatubo ejected a volume of 4.25
cubic miles of volcanic rock. (http://www.cotf.edu/ete/modules/volcanoes/vsizeserupt1.html)]
What
are the general dynamics of these lahars? (i.e., how
far do they flow, does this simply depend on rain levels,
topography, etc.; do lahars simply act as a muddy glacier
and eventually "disappear," and so on.)
[They can
travel over 50 miles and can reach speeds of over 40
mph. Mt. Rainier has a long history of eruptions that
caused lahars. About 5,800 years ago, a sudden collapse
of the 16,000 foot summit sent a lahar containing over
one-half cubic mile of material thundering down the
White River valley. This wall of mud was 100 feet high
and it buried an area of 125 square miles including
the area where the cities of Kent, Sumner, Auburn and
Puyallup now are located. It finally stopped beneath
the waters of Puget Sound. It is known as the Osceola
mudflow, one of the largest]
What is
the impact of the lahars on streams and rivers?
[As Brian
mentioned, lahars may choke the streams, but rivers
may also direct their flow. At Mt. St. Helen's, after
the outrush of the avalanche and ash cloud, enormous
mudflows slid off the mountain down several of the adjacent
river valleys. These flows were caused by water from
blast-melted glaciers and snow that mixed with the already
powdered rock to form pasty, muddy flows. These hot
and cold masses of mud swept down the valleys of several
rivers, sweeping away buildings, vehicles, trees, and
even bridges. Trees amounting to more than four billion
board feet of salable lumber were damaged or destroyed
by the near-supersonic lateral blast of rock, ash, and
hot gases. One of these flows even reached and blocked
the shipping channel of the Columbia River, 55 miles
downstream. (http://www.cotf.edu/ete/modules/volcanoes/vsituations4.html)]
How could
we estimate the primary blast area that would result
from a Mt. Rainier eruption?
[Using the
Mt. St. Helen's eruption as a guide, all those within
5 to 10 miles of the volcano on the north side, scientist
and layman alike, were doomed. Some took a few quick
pictures. Then, realizing their situation, most ran
or tried to drive away from the approaching cloud of
dust and steam. The ash-laden cloud engulfed the area
with a force sufficient to strip huge trees bare and
uproot or break them off at ground level. The temperature
within the cloud reached 500ºF and was sufficient to
cause serious burns and start fires. The rock avalanche
roared over Spirit Lake and the valley of the North
Fork Toutle River, burying them under layers of rock
up to several hundred feet thick. (http://www.cotf.edu/ete/modules/volcanoes/vnarrative3.html)]
What are
pyroclastic flows?
[Ash flows
are turbulent mixtures of hot gases and pyroclastic
materials carried with such force and speed that they
level anything in their paths. The French term, "nuee
ardente," for "glowing cloud" is used
to describe the intense heat carried through the air.]
Can the
release of SO2 from the eruption cause acid
rain?
[Sulfur is
largely responsible for the problem of acid rain. It
is oxidized into sulfur dioxide in the atmosphere that
creates sulfuric acid when combined with atmospheric
moisture. Nitrogen in the atmosphere oxidizes into nitrous
oxides that produce nitric acid when combined with atmospheric
moisture.]
What was
the character of past eruptions in the Cascade chain?
[The mud
flows from Mt. St. Helen's dumped more than 75 million
cubic yards of sediment into rivers, valleys, and reservoirs.
Several pyroclastic flows left about 0.05 cubic mile
of deposits in this area. About 230 square miles were
devastated by the eruption." (The Eruption, NGDC,
p.4).]
To affect
the worldwide temperature, how much dust and ash would
have to be added to the upper atmosphere?
[With Mt.
St. Helen's I did find out that in addition to the ash
cloud that stayed near the ground, millions of tons
of fine ash were thrown high into the air and carried
hundreds and thousands of miles downwind. These clouds,
easily seen in satellite images, dropped several inches
of ash over many communities and agricultural areas,
ruining machines and crops. I would suggest we look at
impacts on the state of Washington rather than worldwide
consequences.]
What is
the elevation of Mt. Pinatubo compared to Mt. Rainier?
[Mt. Pinatubo
is on the island of Luzon in the Philippines and rises
to an elevation of 4,875 feet (Mt. Rainier's elevation
is 14,410 feet).]
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