Iceland review - 2015, Síða 32

30 ICELAND REVIEW
Volcanologist Haraldur Sigurðsson
was off by five days when pre-
dicting the end of the eruption in
Holuhraun. Starting on August 31, it lasted
almost six months, or 181 days, concluding
on February 27. Using a simple mathemat-
ical formula with the help of his grand-
son, Gabríel Sölvi Wendels, an engineering
student at Reykjavík University, Haraldur
calculated in October that, judging by the
decreasing subsidence of the Bárðarbunga
caldera—the volcano which lies under
Vatnajökull fed the eruption north of the
glacier by an underground channel—and
hence reduced pressure of magma, the
eruption would end on March 4.
SCIENTIFIC BREAKTHROUGH
“It’s the first time in history that the end
of a volcanic eruption has been predicted,”
Haraldur maintains. “There are three steps
to a scientific theory. First, data is collect-
ed, in this case about the subsidence of the
Bárðarbunga caldera. Next, a theory or
model based on the data is made—which
isn’t necessarily correct and must be tested.
Finally, a forecast is made and if it proves
correct it supports the theory on which
further forecasts can be based.”
Geophysicist Freysteinn Sigmundsson
agrees. “It tells us that the system is … basi-
cally rather simple and the question is now
what will happen with the magma cham-
ber below Bárðarbunga in the future,” he
told national broadcaster RÚV. Freysteinn
reasons that Haraldur’s theory can be used
to evaluate further developments in the
volcano.
“In 1978, my colleague Steve Sparks and
I put forth a theory about lateral magma
flow in volcanoes like Bárðarbunga, Askja,
Grímsvötn and Krafla, but we didn’t have
the opportunity to test it,” Haraldur says
of the origins of his theory. “When the
magma intrusion began in Bárðarbunga
on August 16, with magma reaching the
surface on August 29, there was a question
whether the theory could be put to the test,”
Haraldur explains. “We had data about the
subsidence and it followed a certain process
with unbelievable accuracy. It wasn’t linear
but a curve, which with time became flatter.
And so a formula could be made: once the
curve would become horizontal, the erup-
tion would stop, as the curve indicates the
outflow of magma.
“Gabríel Sölvi calculated when the curve
would become horizontal and came up
with the first week of March. And we stood
by it. The curve proved remarkably even,
there were almost no daily fluctuations, it
was almost perfect,” Haraldur excites. “It
was simple in this case because the magma
chamber is probably very large so that
outside disturbances have no effect on the
model. It can no doubt be used on other
eruptions in the future.” However, the
significance of Haraldur’s prediction is dis-
puted. “Some scientists claim it was mere
coincidence,” he says.
WAYS OF A VOLCANO
The eruption in Holuhraun was preceded
by a series of earthquakes which began
in Bárðarbunga on August 16. “We had
observed increased activity since May
and we had been in contact with the
Department of Civil Protection. Then,
on August 16 an immensely powerful
earthquake series suddenly began and it
immediately became clear that this was a
case of magma on the move,” says Kristín
As the eruption in Holuhraun has come to an end, scientists evaluate its
effect and discuss what Bárðarbunga volcano may be up to next.
BY EYGLÓ SVALA ARNARSDÓTTIR. PHOTOS BY PÁLL STEFÁNSSON.
FIRE OUT