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| Oberlin's First Volcanologist
Seeks Answers to Eruptive Questions |
by Anne C. Paine | photos by Al Fuchs
January 6, 2003 |
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Assistant Professor of Geology Jonathan
Castro found his fascination for volcanoes in a most unlikely
place: a freshman speech course at Humboldt State University.
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Castro holds a piece
of volcanic rock, the subject to which he has devoted
his professional life. Like all volcanologists,
Castro hopes that if scientists can better understand
the behavior of volcanoes, their disruptive effect
on people’s lives can be minimized. |
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To fulfill a class assignment, the young geology major
presented a talk on the 1902 eruption of Mount Pelée
on the Caribbean island of Martinique.
"There was precursor activity just a few hours before
the eruption, but authorities didn't evacuate residents
in a timely manner," Castro said. Volcanoes are highly
unpredictable, and rumblings don't always result
in volcanic activity. But "an eruption can happen
in a matter of hours," Castro said.
Martinique's decision not to evacuate turned out
to be a deadly gamble. The eruption destroyed the city
of Saint Pierre, killing 30,000 inhabitants.
In completing his assignment Castro confirmed his vocational
interest, which led him to graduate study at the University
of Oregon and finally to Oberlin, where he is the first
volcanologist ever to be a member of the faculty.
"It was very intriguing to me that people all around
the world live on the flanks of volcanoes without much
concern for their danger," he said.
"Volcanology as a science is directed toward mitigating
volcanic hazards, or lessening the blow of volcanic eruptions
on humans," Castro said. "If we can better predict
how long the explosive phase of an eruption will last,
we can better prepare for evacuations and predict how
long people's lives will be disrupted."
Volcanic eruptions can be effusive or explosive. Effusive
eruptions are destructive, but explosive eruptions are
deadly.
In effusive eruptions, the magma (molten rock from deep
within the earth) is thin and runny, and it flows easily
out of the vent. Lava flows rarely kill people because
they move slowly enough that people can get out of harm's
way.
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| Castro makes some
adjustments on the scanning electron microscope.
Castro was the principal writer of Oberlin’s
successful grant application to the National Science
Foundation for the machine, which he uses extensively
in his research. |
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In explosive eruptions, viscous and sticky magma prevents
gases from escaping; these gases build up and explode
violently from the vent, spewing hot clouds of gas and
lava fragments into the air. As they descend, these hot
clouds destroy almost everything in their path. Explosive
eruptions also spew ash into the air, and if the falling
ash is heavy enough, it can suffocate plants, animals,
and people.
"My current research is focused on understanding
explosive and non-explosive volcanic eruptions,"
Castro continued. "It's common that when there
is an eruption in the U.S. West, it starts with an explosive
phase. Then there is a quiescent, or calm, lava flow.
I try to figure out what controls the transition from
the explosive phase to the quiescent phase."
Much of Castro's research is focused on the Inyo
Domes in the Mammoth Lakes area of eastern California,
in the Sierra Nevada range. A lava dome occurs when thick,
slow-moving lava collects around the volcano vent and
forms irregular mounds, or domes. The most recent Inyo
eruptions occurred between 500 and 600 years ago, making
them among the youngest and best-preserved lava flows
in the United States.
Castro uses Oberlin's new scanning electron microscope
extensively in his work, examining the texture of samples
of volcanic material produced during explosive and effusive
stages of eruption. By examining the size, number, and
shape of mineral grains within the volcanic material,
Castro can learn a great deal about the eruption history.
"These textures have recorded in them the path that
the magma traveled before the eruption. By path, I mean
how fast it traveled, what distance it traveled, and what
sorts of pressure changes the magma underwent. I'm
reading rocks, basically, like an archeologist would read
an excavation of an ancient city. I can describe the behavior
of the magma beneath the earth and the chemical changes
in the rock that happened over time," Castro explained.
Taking his research one step further and trying to predict
volcano behavior requires working with geophysicists,
who do real-time monitoring of what's happening in
the depths of volcanoes. "It's definitely a
collaboration," Castro said, who works with colleagues
at the University of Oregon, the University of California,
Berkeley, and the University of Alaska, Fairbanks.
Castro has witnessed—from safe distances—several
volcanic eruptions, including Etna and Stromboli in Italy
and the large Kilauea volcano in Hawaii.
"But I'm still waiting to see my first explosive
eruption," he said.
That's a wish perhaps only a volcanologist would
ever want to come true. |
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