Iceland review - 2014, Side 25

ICELAND REVIEW 23
When Bárðarbunga volcano stirs, everyone in
Iceland listens. It’s the country’s biggest volcano,
and it’s located smack-bang in the middle of
the Icelandic hotspot (volcanic regions thought to be fed
by underlying anomalously hot mantle often near tectonic
plate boundaries). But it’s a difficult mountain to study, as
it’s entirely buried underneath Vatnajökull, Europe’s largest
glacier. At some point in the distant past, the volcano col-
lapsed during a catastrophic eruption, resulting in the for-
mation of a caldera, or a huge, 10-km (6-mile) wide central
cavity that is about 700 meters (2,300 feet) deep. The cavity,
or caldera, is filled with ice. Somewhere within the caldera,
now at a depth of over 100 meters in the ice, lies the wreck
of a Skymaster DC-4 aircraft, Geysir, that crashed there in
September 1950 during the early days of the Icelandic avia-
tion pioneer Loftleiðir, now Icelandair. It was a cargo flight
and all six crew members were rescued.
Bárðarbunga began to shake violently on August 16, 2014,
lasting two weeks. Then, the earthquakes migrated first to
the southeast and quickly changed direction to the north-
east. Scientists determined that the earthquake activity was
caused by the formation of a dike, or a magma-filled fissure,
that was fed from the underground reservoir of the volcano.
Dikes are the plumbing system of Icelandic volcanoes, and
they can carry molten rock or magma for a distance of tens
of kilometers away from the volcano in vertical fractures
within the crust. This earthquake activity was focused in two
areas. A series of large earthquakes, up to magnitude 5.7,
occurred along the caldera margin of Bárðarbunga, while a
series of earthquakes began to the east of the volcano. This
series created a line of earthquakes that stretched further
and further to the north, up to a distance of about 70 km
from Bárðarbunga and beyond the glacier’s edge. These
earthquakes represent the creation of a great fracture, or
crack, in the earth’s crust north of the volcano. Through this
vertical fracture, the volcano is sending a stream of molten
rock or magma to the north within the crust.
Finally, at the end of August, the magma-filled dike
reached the surface and a fissure eruption broke out in
Holuhraun, first for a few hours on August 29, then again
on August 31, and it has carried on since. Holuhraun is
an old lava field 50 km to the north of the volcano. For
Icelanders, the eruption could not have happened in a bet-
ter place: the region is a remote desert at the northern edge
of the Vatnajökull icecap. Red-hot magma at temperatures
of 1,175°C (2,150°F) flowed from the 1.6-km (1-mile) long
fissure, spreading lava over the sandy desert and over the old
lava at Holuhraun, which formed in the exact same spot in
1797. When the new eruption began, the floor of the caldera
of Bárðarbunga began to subside, including the thick icecap
sitting on top of it. It has been sinking at a rate of about 0.5
meters per day.
Although very remote, the eruption could potentially
have two serious impacts. One of these is the threat of mas-