July 2016 – ICELAND – Two earthquakes of magnitude 3.2
occurred in the Katla caldera in Mýrdalsjökull glacier around 4:00 AM
this morning. Ten smaller earthquakes followed. Katla is one of
Iceland’s largest volcanoes, and with twenty eruptions being documented
since the year 930, Katla remains on of the country’s most active
volcanoes.
Scientists at the University of Iceland
Institute of Earth Sciences (IES) and the Icelandic Met Office have
been monitoring activity at Katla lately, but small glacial river floods
have been observed in recent weeks in the Múlakvísl river that flows
from underneath the glacial cap. The floods are caused by Katla’s
geothermal hot spots under the Mýrdalsjökull glacier in South Iceland.
“This seems to be an annual occurrence, but we still have a reason to
closely monitor the situation,” says Dr. Páll Einarsson, geophysicist at
the IES.
“The last large eruption in Katla was
in 1918, but in the meantime there have been three events that indicate
volcanic activity underneath the glacier. First in 1995, then in 1999
and most recently in 2011 when a glacial flood in Múlakvísl River took
out a bridge on the main road,” says Dr. Einarsson. “All of these
incidents share some similarities, there were earthquakes, rumbles, and
glacial floods. There are signs that suggest that small volcanic
eruptions did take place underneath the glacier but they were not large
enough to break through the icecap. The icecap is fairly thick and only a
large eruption would manage to break to the surface.”
Katla has not erupted for some time and
some locals believe the volcano is long overdue. Dr. Einarsson points
out that volcanoes do typically not erupt at a certain intervals and any
talk of Katla being overdue is misleading. “Katla seemed to be fairly
predictable for the past three hundred years, but it erupted twice a
century, typically in the 20s and 60s,” Dr. Einarsson says, but the
volcano erupted in 1625, 1660, 1721, 1755, 1823, 1860 og 1918. “This
perceived predictability led people to expect a large eruption in around
1960, but we’re still waiting for it. Volcanoes are unpredictable,” he
adds.
How bad would it be?
How bad will it be if Katla erupts? The
Katla eruption in 1918 produced an enormous ash cloud and five times as
much ash as the 2010 Eyjafjallajökull eruption that halted air traffic
in the North-Atlantic and across Europe. Such a large eruption is likely
to disrupt air traffic and cause destruction of property and local
infrastructure.
In addition to an ash cloud, large
eruptions in Katla are accompanied by enormous floods when melted snow
and glacial water, mixed with mud and pieces of ice, break out from
underneath the icecap and flow to sea. In the last large eruption in
1918, the Southern coast was extended by 5 km by the laharic flood
deposits. The most likely path of such a flood is to the South across
Mýrdalssandur area, an unpopulated area east of the town Vík in
Mýrdalur. –Iceland Monitor
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