Interview with Dr. Stephen McNutt,
Research Professor Volcano
Seismology, Geophysical Institute of Alaska. USGS.
Fairbanks, Alaska 22.07.2002.
"Volcanos give rise to numerous geologic and hydrologic
hazards. U.S. Geological Survey (USGS) scientists are
assessing hazards and many of the almost 70 active and
potentially active volcanoes in the United States.
They closely monitor the most dangerous ones and are
prepared to issue warnings of impending eruptions or
other hazardous events."
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Interview Summary
"Almost 300 specialists work at the Geophysical Institute of
Alaska in Fairbanks, making it one of the biggest Institute
of its kind. About 20 persons are studying volcanoes fulltime and there
is about 15-20 persons who studying earthquakes.
Professor McNutt's speciality is seismology with the studying
of earthquakes and the deformation of the ground by sensors
on the ground and by the use of satellite technologies.
At the same time geologists are studying rocks, the structure of the
rocks, deposits and are mainly interested
in the history of the
past eruptions trying to gather information of how (what type)
and how often a volcano was erupting in the past.
Additionally there is the field of geochemistry - where we are
trying to find out how the rocks formed in the first place.
The gathering of all these information allows the forecasting
when an eruption will occur and what type of eruption will occur. "
Volcano eruptions cause many different threats.
"The better we know a volcano, the better we are able to predict its
behavior and issue appropriate warnings."
Example of an 1989 Eruption of Mt. Redoubt that put KLM
Flight 867 at great risk.
Nowadays modern technology is used to monitor the volcanoes
in Alaska and the Aleutean Islands.
"24 volcanoes are permanently monitored with seismometers.
41 of them are historically active, so more than half of the active
ones are covered by now."
"Satellite technologies in use:
1. Geostationary satellites are situated at around 22000 km
above ground and give a fairly reliable but low resolution image
every 15 minutes. They show bigger eruptions and bigger plumes
of volcanic ash.
2. Polar orbiting satellites help to find hot spots or plumes
(volcanic ash) on the ground with a good resolution. As they
cruise much closer to the ground they give a very detailled picture
of whats going on on the ground..
3. The most interesting satellite in use is an AVHRR (Advanced
Very High Resolution) Radiometer which takes
pictures at
different frequency bands sensitive to heat. They show a change
in temperature on the ground as well as plumes (volcanic ash
clouds). A plume might look like a cloud but has different
frequencies which are revealed by this radiometer.
4. The fourth technology in use is Interferometry, which is
comparing pictures of the same area which are taken at
different times. Interferometry allows to see deformation in
all 3 dimensions."
One of the
Shishaldin - one of the most active volcanoes - monitored
closely at present time:
Detailled combination of data on Mt. Shishaldin:
General plate movement around the ring of fire:
"Assuming that the North American plate is stable, the Pacific
plate (the largest plate on the earth) - is moving 8 cm per year
to the north west. As the Pacific plate is moving underneath
the American plate, part of the earth which is moving under
the North American plate melts with the lava which is already
there and then moves upwards. This process is called
"subduction process" and goes on around the ring of fire."
In Alaska the strongest friction and the strongest earthquakes
happen about 60 miles inland:
"About 95% of the seismic energy is produced around
the "Ring of Fire" (ring around the Pacific plate)."
"The
challenge in volcano research is to find out, when a
volcano behaves strange.
Each volcano has its own pattern. While one volcano may
have hundreds of tiny earthquakes every day - another has
only one earthquake every 3 months - still, these different levels
of activites can be normal for each place.
The most typical unusal activity in
a seismological point of
view is when a volcano starts to produce more earthquakes
than he normally does. The second type of signal is more
subtile: A volcano can start to produce a continuous type of
signal which is called "volcanic tremour". This signal is
always produced while he is erupting but it can also be
produced before. The trouble is, that the signal can ressemble
noise, particularly at a stormy day. If the signal begins very
gradually You can only "hear" it at quiet days. This means that
we have to wait for the signal to get strong enough to be sure
of its characteristics. This for example was the case that
happened a couple of years ago with Mt. Shishaldin where
we were able to get hold of the signal a couple of months
before he was erupting.
In combination with all the other information (geology
a.s.o)
appropriate warnings can be given to the public and the
different organisations (f.e. in the field of air traffic)."
Goals for the
future:
- New network of seismometers. The goal is to monitor all of the
active volcanoes in the area
- Get deformation instruments (latest GPS-Technology) on the
ground
Problems:
- Probably the biggest problem out in the
field is the weather. It
normally would take a day to put a station out but bad weather
conditions many times do not allow flying and working on the ground
can be a problem too.
- A big problem is always politics. It takes a big effort each time
to convince people that things have to be done and that the
resources (money&people) are given to get further on in
achieving our general goals
- Another problem are the logistics. Some areas are quite difficult to
get to. As we need to organise everything that we will need out
there on our own (fuel, helicopters, food, survival gear) these
expeditions can be quite expensive and need a lot of preparation
- Another problem can be the bears when working on the mainland
or at islands nearby. Right now further out in the Aleuts we
fortunately
do not have this problem"
Personal biggest current wish of Dr.
McNutt:
"...and - If I had a technical wish:"
"It would be great if someone invented a better powersystem - means: ..new
and stronger solar- and battery technology, 'cause that's the reason of
most of the failures of our existing data network."
and:
"New
technologies that prevent signals to cancel themselves out at high
tides or at certain snow conditions because they interfere with each
other and make us lose the data."
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With
many thanks to Dr. Stephen McNutt, Jon Dehn and also to the people
that we might
have disturbed during our visit:
Marius
& Franziska Staerkle
