Iceland review - 2015, Side 33

ICELAND REVIEW 31
Jónsdóttir, coordinator of the Icelandic
Met Office’s natural hazards division. The
Met Office monitors 70 seismographs and
70 GPS sensors located on volcanoes and
in seismically-active areas in Iceland and
its staff were quick to put up more meters
in the Bárðarbunga area. Kristín adds that
because of the EU-funded research project
Futurevolc, which had been launched prior
to the eruption, important instruments had
already been installed in the field, stream-
ing data real-time, so the developments in
the volcano could be followed closely.
“The earthquakes moved away from the
caldera, to the northeast and north,” Kristín
describes of the development. The pattern
indicated that magma was channeling its
way underground, creating a 48-km (29-
mile) long intrusive dike, which ended
in the already existing Holuhraun lava
field, north of the glacier. “It was a relief,”
Kristín admits. “A minor sub-glacial erup-
tion did occur but it was extremely lucky
that magma didn’t surface through the
ice. There was no ash, no floods.” After
an eruption which lasted a few hours on
August 29, a 1.5-km (1-mile) long fissure
opened up, spewing 1,175°C (2,150°F) hot
lava from three craters, Suðri, Baugur and
Norðri, as high as 100 meters (328 feet)
into the air. Lava flowed over the old lava
field, onto the sands around it and into the
riverbed of glacial river Jökulsá á Fjöllum,
which retreated.
“The lava spread out over a plain of fine
sand in an area called Flæðurnar, north of
Dyngjujökull [outlet glacier], which gets
whirled up by the wind, causing sand-
storms—an annoyance for people in East
Iceland. Now the lava binds a large part of
the dust,” Kristín reveals. Eventually, the
new lava field stopped expanding and start-
ed thickening, while the edges around the
craters grew taller. The eruption remained
fairly stable until mid-January. One month
later it was reported that the eruption was
likely to be in its final days.
BIGGEST AND HOTTEST
The Holuhraun eruption is the largest
lava eruption in Iceland since the 1783-
1784 Laki eruption. During the Holuhraun
eruption, 1.5 cubic km (0.36 cubic miles) of
lava were emitted, covering 85 square km
(33 square miles), which is the same size as
Iceland’s largest lake, Þórisvatn in the south-
ern highlands. For comparison, Manhattan
measures 59 square km. Holuhraun is also
the ‘hottest’ eruption the world has seen
this century, at one point releasing one
third more energy than Russian volcano
Tolbachik, which erupted in 2012-2013 and
placed second on the list, as concluded in a
study led by Robert Wright of the Hawaii
Institute of Geophysics and Planetology.
The lava is approximately 40 meters (131
feet) thick at the lava field’s highest points.
The crater is 70 meters tall, 100 meters
wide and 600-700 meters long. The average
thickness of the lava is 15 meters, or similar
to a five-story building.
GAS, GAS, GAS
Even though Holuhraun was the biggest
eruption Iceland has seen in centuries,
it occurred in a favorable location in the
remote northeastern highlands, pos-
ing no direct threat to inhabited areas.
Nevertheless, toxic volcanic gases, primar-
ily sulfur dioxide (SO2), have proven a
hazard with Holuhraun being the most
gas-intensive eruption in Iceland since the
18th century. At the eruption site, where gas
masks and gas meters are a requirement,
SO2 levels have reached 130,000 µg/m3,
while 21,000 µg/m3 is the highest level
recorded in an inhabited area, in Höfn,
Southeast Iceland, in late October. At lev-
els above 2,000 µg/m3—which have been
recorded across the country—warnings are
issued and people advised to stay inside
with the windows closed and heaters on. As
a reference, an hourly concentration of 350
µg/m3 is the maximum safe limit for human
exposure.
While SO2 hasn’t been picked up in
inhabited areas since the eruption ended,
gas is still being released at the eruption
site as it takes months or years for the
lava to degas. “During a recent fieldtrip
we measured high levels of gas, even with
the strong wind. There was still a distinct
haze over the lava field,” describes Sara
Barsotti, coordinator for volcanic hazard
at the Icelandic Met Office, of the scene in
mid-March. “It will not be safe to walk on
the lava for several months to come.”
Samples taken in all regions have indi-
cated that snow has turned acidic as a
result of the volcanic gases. “A research
project is ongoing. Samples from fishing
rivers and water reservoirs will be taken in
spring but all this changeable weather has
helped—some of the toxins have already
been washed away,” Víðir Reynisson, direc-
tor of the Department of Civil Protection
and Emergency Management, states. “The
levels will peak immediately after spring
thaw but this will not be a lasting problem.”
Víðir is confident that come summer, it will
be safe to release sheep to the highlands, as
is customary in Iceland, and for hikers to
drink water from brooks.
RISING AGAIN
Bárðarbunga is one of the biggest volcanoes
in Iceland and has produced massive erup-
tions in the past. Scientists disagree wheth-
er it will erupt again in the near future.