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A Trip to the Aleutian Islands
by Dr.
Nathan L.B. Bangs
 The following article was written by our son
Dr. Nathan L. B. Bangs, a geophysicists who conducts research at the
University of Texas Institute for Geophysics. Nathan is a graduate
of Wildridge Academy, received his undergraduate degree from
Williams College, and his doctorate from Columbia University. He
lives with his wife Alex and 2 year old daughter, Hannah, in
Austin.
I was on my way to work, but this was
not a typical trip to the office. Instead of the 10 minute drive in
aggressive Austin, Texas traffic, my wife dropped me off at the
airport.  I was on my way to join the research
ship, the R/V Maurice Ewing, anchored in Dutch Harbor, Alaska. For
the next month we would acquire the data we needed for a major
research project along the remote stretches of the Aleutian Islands
and the southeastern Alaskan coast, which we had been planning for
years and eventually had convinced the National Science Foundation
to fund.
On these trips, I usually ask for a
window seat. As a geologist, there are few opportunities to see
continental landforms at the large scale one has from 30,000 feet,
and a trip in an airplane gives scope on the dimensions of earth
that just can't be appreciated or imagined from the ground.
Fortunately on this trip the weather was clear. We crossed the
plains of the central United States, the Rocky Mountains to Salt
Lake City, then changed planes and headed north again along the
inland waterway, took a left at Yellow Knife, over the Wrangell-St.
Elias Range, and landed with a great view of Denali (Mt. McKinley)
in Anchorage. Even though this was a domestic flight, you could not
get to Dutch Harbor in one day. It took almost twice the time to
reach Dutch Harbor as it took to get back from my last cruise even
though that one ended in the world's southernmost city, Punta
Arenas, Chile.
On the second day, and final leg of my
flight, it became apparent that I was heading to a destination that
is not in most travel agent's computers. I should have realized this
was an unusual trip when the ticket from Anchorage to Dutch Harbor
cost almost the same as the flight from Austin to Anchorage. The
plane was loaded with people who obviously had a good reason to be
there and not just tourist or people visiting relatives. Dutch
Harbor is the place where urban legend claimed you could make tons
of money canning salmon in Alaskan fisheries during the summer
between semesters at college. It was a stop during the great Alaskan
gold rush, and it was a military outpost that was bombed by the
Japanese during WWII. From the looks of the plane it was clear this
was a trip where they meant business. Actually, about half the
normal seating space on our 737 was used for cargo.
During our flight the sky was clear,
which was unusual for this part of the world and fortunate for me to
see the landforms I was hoping to view. Anchorage is near the
eastern edge of the Aleutian volcanic chain, which extends west for
more than 2,500 miles. As we flew along, every few minutes we passed
a cone shaped mountain that made up the snow capped volcanoes of the
Aleutians. One of them, Redout, about a half hour from Anchorage,
had actually erupted in 1987. A jet flying at night accidentally
flew into the erupting ash. It snuffed out all of its engines, and
gave the passengers a scare, but fortunately the plane landed safely
after getting some power back. We had clear skies that allowed any
pilot to see billowing clouds of ash if it should happen again
during our flight. Even without that story, it was obvious that
these are active volcanoes. They had a nearly perfect conical shape,
with few gullies or channels. The lava was erupting often enough to
keep pace with the erosion of the glaciers and rivers. In fact,
these very volcanoes were a big part of our study.
The land mass of the North American
continent and the crust beneath the Pacific Ocean are actually
colliding even though it is too slow to notice. The Pacific plate is
moving beneath the North American plate, subducting, at a rate of
about 8 cm/ yr. Although the motion of the plates is not noticeable,
the effects of this large scale plate motion were obvious from the
view out of my plane window. The movement of the Pacific plate
beneath the Aleutians forces rocks near the surface deep into the
earth where they are subjected to intense pressure and temperature
and consequently melt. Fluid magmas rise through the crust,
resulting in the volcanic eruptions and eventually the tall volcanic
peaks that I saw below. Associated with this process are also most
of the world's largest earthquakes, such as the 1964 event that
devastated parts of Anchorage. It was these plates, and the
structures produced from their movements that were the subjects of
our study.
From the plane we could even see some
of our project objectives. When we left Anchorage, the volcanoes
poked up through the large continental mass that comprises Alaska.
But as we flew farther west, the volcanoes form individual islands
that extended farther and farther from the continent, out into the
middle of the North Pacific. There, the North Pacific plate subducts
beneath ocean crust of the Bering Sea rather than beneath
continental crust of Alaska. From the plane, I could see this chain
of volcanoes appeared to be stepping down and foundering into the
sea. From the plane it did not appear that the volcanoes were any
different, the only difference was that the continent ran out as you
headed west. We wanted to investigate how new continental crust,
which forms with each new eruption along these islands, is created
on continents and in the middle of the ocean where no continents had
previously existed.
Continents protrude up out of the
oceans because continental crust is lighter and thicker than the
crust that forms beneath oceans. Plate tectonics explains how pieces
of continent move around the surface of the earth, but there is no
explanation of how continental crust is generated and evolves to its
composition, which is similar to granite. Even though volcanoes are
far more common and active beneath the worlds oceans, those
volcanoes rarely poke up out of the sea. Outside my plane window I
could see volcanoes that poked hundreds of feet out of the ocean,
and we believed that the volcanic processes that created these
islands were the ones responsible for the genesis of new continental
pieces that would eventually collide with existing continental
masses and accrete to form new landmass.
What we wanted to know was the
structure beneath the volcanoes, which controls the geochemical
processes that generate magmas and their subsurface movement. How
did the structure and the subsurface tectonic and geochemical
processes change beneath this obvious transition from volcanoes on
an Alaskan continental host to a host in the middle of the Pacific
ocean crust? But how do you examine the structure of the crust that
is not only underwater and not accessible to a rock hammer, but
extends down 30 miles below the seafloor? This is why we needed the
R/V Ewing, and why we designed a seismic experiment. While direct
sampling is possible with the Ocean Drilling Programs drilling ship,
drilling usually can make it no more than 1 mile into the crust and
that is extremely expensive and it would take about 2 months time.
The alternative is to try to sample the deep earth remotely. This
can be done by sending a sound wave directed down into the crust and
listen to any reflections that return. Bats use similar techniques
to "see" as they fly, and marine mammals also do so in the oceans.
Our seismic technique can "see" the subsurface structure after a
great deal of manipulation and processing of recordings made on the
Ewing.
The Ewing is operated by Columbia
University, which acquired her in 1990 from Petro Canada. The Ewing
was designed for seismic work, but the down turn in the oil business
in the late 1980s forced Petro Canada to sell her and allowed
Columbia to make her available to the academic world. She is the
most capable seismic ship in the academic world. She is the only
ship capable of sending a large enough sound signal to reach 30
miles and return to the surface to be recorded by her sensitive
hydrophones. With her capability and the hard work of its 20 crew
members and 18 scientists, we could remotely sample the subsurface
down to 30 miles even though our results are nothing more tangible
than several hundred computer tapes. This shipboard seismic
surveying of the deep subcrustal structure was to be conducted along
the Aleutians and across the island chain where it breaks in between
the volcanic islands.
Thoughts of what was happening outside
my plane window distracted me from the work I had brought along with
me to do on the plane. Before I left, I had been asked to review
proposals by the National Science Foundation. Proposals that were
similar to the one we had submitted to NSF to request funds to
conduct the survey I was headed for. It is this peer review process
that the whole system of conducting good science depends. It is a
long and thorough process that requires the efforts of several
experts in each field and experts outside the field to evaluate the
merits and potential problems of any experiment, particularly
experiments that are as costly as a seagoing program. This Aleutians
program took almost 5 years from the time it was conceived until the
cruise began. It would be 3 more years working on the data. In the
frenzy of preparing to be out of the office for more than a month,
and to prepare for the cruise, I had not finished my reviews.
Because of the demands of my academic research position, I try to
utilize whatever moments I can, and a long airplane ride can't be
wasted. I knew if I did the review on the plane, I could type it up
while we were in port, and send it to NSF from the ship via e-mail,
our main means of shipboard communication. Even though the deadline
was still a few days away, I knew it had to be done before getting
underway because a few miles from port and I would be far too
seasick to want to read, or type on the computer.
It happens every time. Even the best of
sailors feel ill when they leave port, but most of them just won't
admit it. I suffer more than most. The only difference between the
first time I went to sea on a cruise 10 years before and this time
is that now I know that I will recover enough to function reasonably
in probably 3-4 days. On my first trip I didn't know that I would
ever be able to do anything other than be miserable aboard the
rocking ship. On this trip my adjustment will surely depend on the
weather, which is not good at these high latitudes. I'm hoping the
summer months will mean quiet conditions, it is the best time of
year to avoid big storms. I guess that there were enough select
memories from the last cruise, that I have lost my memory of the
shipboard motion and how unpleasant it is at first. Otherwise I
don't know why I am not apprehensive about heading back to join the
ship once again.
As the plane began its descent, I had a
strange recollection. When I was 10 on a trip with my parents and
several other teenagers, we went out to dinner. Everyone said that
they wanted to be daring diners and try something new, the braised
calves brains. To show I was as sophisticated as these teenagers, I
ordered the brains, but it was not until I saw the plates arrive
that I realized that everyone else had ordered something more
pedestrian, and I was the only one who ordered the calves brains. On
this trip, I was alone because all of the other participants were
from other institutions such as the University of Delaware, Columbia
University, Woods Hole, and Stanford, and they were not on my
flight. Was there really going to be a ship there waiting for me?,
or had I ordered calves brains once again. If you were going to
screw up, or be dooped, it was one thing to land at one of my
favorite spots, Barbados, and another to land in Dutch
Harbor.
As the plane pulled in for a landing it
was obvious we were on a small steep-sided volcanic island in the
middle of the ocean. The steep hillsides were lush with green
vegetation; a product of the frequent rains, and the mineral rich
soil of the volcanic ash. The plane flew up a harbor, made a steep
decent and left turn simultaneously. From my side of the plane I
could see the water below, a steep cut in the mountain for the
runway, and another harbor at the end of the runway. The plane pulls
out of its turn, and immediately hits the runway and brakes. Flat
spots on the island are so limited that the short runway makes for a
memorable landing. I discovered later that the end of the runway
doubles as part of a main road around the island, and a gate comes
across to switch from roadway to runway use. After what seemed to me
to be a controlled crash, the flight attendant said, "that was a
pretty good landing, for Dutch Harbor."
When I got off the plane, some of the
rest of the scientific party was there to meet me and take me to the
ship. The Ewing was being loaded with food stores for a month, fuel,
scientific equipment, the new crew members, and the scientific
party. We sailed for 28 days and saw lots of whales and other marine
mammals, smoking volcanic islands, and an occasional brilliant
sunset that lingered for hours at this high latitude. We returned to
Dutch Harbor with only two storms and seas nearly as flat as a lake
the rest of the time.
It has been three years since the
cruise now, the data are still being analyzed, but we have learned
some fundamentally important things. The most important thing is
that the continental crust that is made in the middle of the Pacific
does not have the structure of crust that makes up the continental
crust of Alaska nor does it look much like the crust of other
continents. The structure of the newly formed Aleutian continental
crust is lacking in the pieces that make up the deeper parts of most
continents. It is clear that these newly formed islands are just at
the beginning stages of the mysterious evolutionary process that
created the habitable parts of earth's surface, the
continents.
You can learn more about the work of
the University of Texas Institute for Geophysics at http://www.ldeo.columbia.edu/.
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