Careful measurements show that the
pulses are dictated by the size of particles
being destroyed as gas pockets blow out.
Lab-made volcanic eruptions (shown)
support field data showing rocks flying
out of a volcano at breakneck speeds.
University of Hawaii at Manoa, agrees;
he is trying to get money to pay for a similarly sophisticated camera setup at the
Big Island’s Kilauea. “It is really a spectacular advance,” Houghton says.
The team is also working to see what
factors control how far large rocks get
ejected from volcanoes. By measuring
the pressure needed to throw a lab rock
of a certain size a certain distance, the sci-
entists can better calculate the immense
forces that fuel eruptions such as those
at Mexico’s Popocatépetl. Alatorre-
Ibargüengoitia has measured rocks trav-
eling up to 400 meters per second, the
same sort of speeds recorded
at Stromboli for much smaller
particles. These larger “vol-
canic bombs” can land as far
as five kilometers from the
actual eruption vent.
“That’s why it’s interesting that our lab
is observing what Jacopo is also seeing,”
says Miguel Alatorre-Ibargüengoitia,
a researcher in the lab. “We can really
replicate what’s going on.”
Experiments in Dingwell’s lab show
the same kind of explosive moments
going on. After collecting and grinding
up rocks from real-world eruptions, the
researchers put the rock powder into
one high-pressure tube meant to simulate the insides of a volcano and then let
the material rapidly decompress into a
second tube. The team has a front-row
seat for this explosion. “This time we’re
watching and deciding when and how,”
Dingwell said in February in Vancouver
at a meeting of the American Association
for the Advancement of Science.
In the lab experiments,
Alatorre-Ibargüengoitia
knows exactly what pressure
the rocks exploded under,
data he can use to calculate
the depth from which the
simulated magma erupted.
“In nature, we don’t know any
of these parameters,” he says.
For their part, Taddeucci and his col-
leagues have already taken their high-
speed camera to three other volcanoes, in
Guatemala and in Vanuatu in the South
Pacific, and seen similarly fast ejections
there. Next, Taddeucci wants to clock
some of the biggest and baddest things
in volcanology: pyroclastic flows, or
massive avalanches of gas and rock that
catapult down the sides of mountains.
Such flows have taken the lives of
volcanologists, including experienced
photographers Maurice and Katia Krafft
in 1991. “You have to find a suitable vol-
cano that you can look at without dying,”
says Taddeucci. s
“When
you’re there,
you’re not
as scared for
the camera
as for
yourself.”
Safety first
The work shows, for instance,
that particles shooting out of
the eruption drop off in speed proportionally to the depth from which they
were ejected. That information, in turn,
can help pin down how much magma is
spewing out of an eruption, along with
how much gas it contains and at what
pressures. Alatorre-Ibargüengoitia and
colleagues described the work last year in
Eventually, the scientists
hope to see their lab work
and occasional videotaping
translate into better monitoring of live
volcanoes. “There’s still an important
gap between experiments and the real
world,” says Alatorre-Ibargüengoitia.
“We are trying to close this gap.”
JACOPO TADDEUCCI
A high-speed camera captures the
size and speed of accelerating particles.
The lab videos show shock waves, like
those Taddeucci sees at Stromboli, driving pulses of material from the eruption.
Earth and Planetary Science Letters.
For instance, colleagues at the University of Hamburg have been tracking
the speed of stuff flying out of volcanoes
using Doppler radar, finding that some
standard monitoring techniques don’t
always accurately reflect the size and
energy of an explosion. (Not that better
information always results in safer conditions; at Etna’s current eruption, tourists have regularly brushed past warning
signs and continued dangerously close
to the summit to take pictures.)
Explore more
s Mount Stromboli info and webcam:
www.eolnet.it/ita/webcam2.asp
