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Above, the dome of the volcano before and after
its collapse.
The dome of the Soufriére Hills volcano on
Montserrat was steaming from heavy rains that had fallen for days
on the warm rocks. By the morning of July 12, 2003, the skies finally
cleared, and another typically humid day began in the tropics. UA
scientist Glen Mattioli and four students were on the east side
of the volcano, in a place called Jack Boy Hill, watching lava as
it surged down the side of the volcano into the sea. For years,
scientists knew that the huge lava dome of the Soufriére
Hills volcano could collapse at any time. When it did, the volcano
released over 300 million tons of lava and deposited nearly 4.5
inches of ash that snapped heavy limbs off trees and destroyed most
of the island’s vegetation and crops.
At sunset, Mattioli headed to the villa where the
team was staying on the west side, while the students remained behind
to watch the flows. The power was out, and so he went to the Montserrat
observatory, which had a generator. He found a radio, contacted
the students, and drove through a slippery blizzard of ashes to
meet them at a restaurant for pizza.
Pamela Jansma, also a UA geologist and chair of the geosciences
department, called later that night to check how husband Glen and
the team were doing. She learned they were in the middle of a major
eruption.
“We didn’t know until later just how major an eruption
it would be,” Jansma recalls.
The peak of the eruption occurred around midnight. Mattioli and
his students were pelted with pumice and a heavy ashfall that lasted
1.5 hours.
“You can’t outrun pyroclastic flows. They consist of
nearly molten materials from microns to meters in diameter, traveling
65 to 165 feet per second. The flows incinerate everything in their
path. They’re energetic avalanches of hot material,”
says Mattioli.
He and his students prepared for a disaster, filling water jugs
and finding candles. Because they had no hard hats, the students
went outside with kitchen pots on their heads to collect samples.
Mattioli and other scientists who study volcanoes know that flows
can reach the oceans, but the instruments this time showed something
they didn’t know: the flows could create tsunami waves.
“They aren’t giant ones, but the physics of both are
very similar. This had never been observed before,” Mattioli
says.
He and Jansma both employ geographic positioning systems in their
research. Mattioli and a team of researchers from Penn State University,
Duke University, and the Carnegie Institution of Washington, in
collaboration with the Montserrat Volcano Observatory and UK colleagues
from Bristol and Leeds, have installed the first volcano monitoring
system of its type on Montserrat.
The researchers drilled four boreholes, each 600 feet deep, around
the volcano’s perimeter, strategically placed in relation
to shallower holes and surface sites.
In addition to the GPS station, the integrated array of equipment
includes seismometers, tiltmeters, and strainmeters. By studying
the entire magma system below the island, the team hopes to learn
more about the volcano’s volatile, often unpredictable cycles
of activity.
The borehole observatory, which will be fully integrated into the
surface monitoring network operated by the Montserrat Volcano Observatory,
will be used to track activity in the magma reservoir and its associated
conduit systems. Data from Montserrat Volcano Observatory can be
viewed in real time and is available to researchers any time of
the day or night on the Internet (http://www.mvo.ms/).
The job scientists face in identifying patterns in nature is formidable.
For example, they know that the events which generate giant tsunamis
occur once every 10,000 to 100,000 years. They don’t know
the most important part of the puzzle: when.
The volcano, which has over a 300,000-year-old history of eruptions,
came alive in 1995 after 400 years of relative quiet. By late 1996,
at the end of the first phase of the eruption, half the population
left.
By 1997, the continuing eruption destroyed the capital, Plymouth,
as well as the southern half of the island.
Mattioli and his colleagues intend to record the volcano’s
short-term dynamics, from 6 to 18 hours, its meso-scale patterns,
which last from a few days to several weeks, and the long-term patterns,
which can last 30 years or more.
What the Early Settlers Couldn't
Know
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Pamela Jansma studies the constant movement of
the Earth as well, but her focus is on the subtle shifts in
the underground plates of the Caribbean.
Because faults form at the boundaries of microplates, researchers
must look at the faults to measure the rates of displacement,
whether the earth is moving at meters or millimeters each year.
“We also look at how sticky they are,” says Jansma.
“Plates moving freely pose a low risk, but those that
are locked will eventually break apart in great force and generate
a large earthquake.”
To illustrate the constant movement of the earth’s surface,
Jansma tells students that in five million years, Los Angeles
and San Francisco will be suburbs, since they are on opposite
sides of the San Andreas fault.
Both Mattioli and Jansma know that one of the most important
benefits of their work will be to protect people in danger from
earthquakes or eruptions. The Soufriére Hills volcano
is an andesite volcano, characterized by explosive eruptions
that lead to more human deaths than any other type of volcano.
Researchers have found evidence that when Europeans arrived
in Montserrat 350 years ago, what they found was a lush but
deserted grassy plain. What the settlers couldn’t know
was why the Indians had all left. As the Europeans settled on
the verdant island, they were also building their new
colony near an active and dangerous volcano.
They certainly could have used an early warning system. |
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