Dr. Claus Rink,
Geoscientist and Special correspondet of Pattaya Mail and Chiang Mai Mail
What is happening in
Iceland?
Volcanic activity in Iceland has been ongoing for weeks
and is getting stronger than before. If you are there it is like you are
living on the surface of what sometimes seems like an entirely different
planet, you become aware of nature’s power to assert itself over our
miserably self-important affairs and to dispose of life in a few seconds.
The ash-plume on the way to Europe (picture: NASA))
The most recent eruption took place late last week. The
volcanic activity sent ash and debris 20,000 to 30,000 feet in the air and
disbursed an ash cloud over northern Europe. The ash cloud over Europe
is so devastating that it has grounded air travel all over the continent
and has stranded many people thousands of miles from their homes and jobs.
Scientists warn that it could be a couple of days or even
weeks before the ash cloud stops posing a threat. In addition, the volcano
eruption in Iceland has also stopped many world leaders from heading to the
funeral for the late Polish President who was killed in a plane crash
earlier this month.
Many now fear that the March and April eruptions of the
Eyjafjallajokull volcano will spawn an eruption at Katla, a much stronger
volcano located in Iceland that would be expected to do massive devastation
should it erupt.
Ash cloud
expanding to Russia
The ash cloud is reported to have extended near Russian
air space and also throughout other areas in Europe. Air traffic is all but
grounded, and many people are having to find alternative transportation
arrangements to get where they need to be.
Atmosphere with ash particles
However, the danger is that the small volcano is just the
beginning and that it will trigger the far more powerful volcano of Katla,
which nestles beneath Myrdalsjoekull.
Chances of
cataclysm high
Eyjafjallajökull is located west of the Katla volcano. It
is an ice-covered stratovolcano with a 2.5-km-wide summit caldera.
Fissure-fed lava flows occur on both the eastern and western flanks of the
volcano, but are more prominent on the western side. Although the
1666-m-high volcano has erupted during historical time, it has been less
active than the other volcanoes of Iceland’s eastern volcanic zone, and
relatively few Holocene lava flows are known.
The eruption is located on an approx. 2 km wide pass of
ice-free land between Eyjafjallajökull and the neighbouring Katla volcano
with its overlying Mýrdalsjökull ice cap. Katla volcano is known for
powerful subglacial phreatomagmatic eruptions producing basaltic tephra
layers with volumes ranging from ~0.01 to more than 1 cubic kilometer. This
could trigger Katla, which is a vicious volcano that could cause both local
and global damage.
Iceland is built on a volcanic magma chamber on the
Atlantic’s mid-oceanic ridge and it has grown used to eruptions. The
southern town of Vik, close to the current eruption, is built on high
ground. They know that if Katla erupts, flooding will be sure to follow.
The island’s worst eruption in modern times was in 1783,
when the Laki volcano blew its top. The lava shot to heights of 1.4
kilometres and more than 120 million tonnes of sulphur dioxide was released
into the atmosphere. A quarter of the island’s population died and it
transformed the world, creating Europes notorious “sand summer”, casting a
toxic cloud over Prague, playing havoc with harvests in France - sometimes
seen as a contributory factor in the French Revolution - and changing the
climate so dramatically that New Jersey recorded its largest snowfall and
Egypt one of its most enduring droughts.
Disaster for airlines and
passengers
Millions of passengers were stranded last Friday after a
huge cloud of volcanic ash from Iceland swept across Europe, grounding
thousands of flights in the biggest air travel shutdown since World War II.
Europe’s air traffic control centre said 75% of the flights were cancelled
because of the “unprecedented” situation and more would follow, while one
airline grounded all its planes in the affected area until Monday.
Europe’s three biggest airports - London Heathrow,
Paris-Charles de Gaulle and Frankfurt - were closed by the ash, leaving
passengers stranded as a global flight backlog built up. Eurocontrol, which
coordinates air traffic control in 38 nations, said only 12,000 of the daily
28,000 flights in the affected zone would take off last Friday, after about
6,000 were cancelled the day before.
Glacier melt causes large
floods
in Iceland
Jokulhlaups (floods of meltwater) reached the lowlands
around the volcano with peak flow around noon on April 14, with destruction
of roads, infrastructure, and farmlands. There were no reported fatalities
as people had been evacuated from the hazardous areas. Tephra fall begins in
southeast Iceland. A second jokulhlaup/lahar emanates from the ice cap.
Activity continued at a similar level with ash generation
and flow of meltwater in pulses. Jokulhlaup/lahar occurred in the evening.
On April 16 some variability occurred in seismic tremor and tephra
generation, but overall the eruptive activity remains stable. The pulsating
eruptive plume reached above 8 km, with overall height of 5 km.
Three large previous eruptions of Eyjafjallajökull are
known in the last 1,100 years (historical time in Iceland). The most recent
began in December 1821 and lasted intermittently for more than a year. The neighbouring volcano Katla erupted then on 26 June 1823. Other instances
include an eruption in 1612 or 1613, and about 920 A.D.
The new eruption is about ten times more powerful than
the eruption before and is located under a glacier. The glacier melted,
causing glacier runs (jökulhlaup) that have twice flooded the south of
Iceland. A vast cloud of ash rose 30,000 feet into the air, endangering
aircraft motors over the north Atlantic.
Katla, which is part of the same volcanic system and the
current eruptions, lies under the Mýrdalsjökull glacier. It has violently
erupted before, causing sudden floods of unthinkable violence (200,000 cubic
meters of water per second; the Amazon’s flow is 10,000 cubic meters per
second) that wiped out roads and farms, taking people with them, and leaving
the survivors on mountaintops that became islands for days at a time.
Although it has historically erupted every 40-80 years,
its last major eruption was in 1918, so it is considered overdue, and there
is speculation that the current activity is a precursor of a new Katla
explosion. Each of the previous three Eyjafjallajökull eruptions since
Iceland’s settlement (920, 1612, and 1821-23) have been followed by a major
Katla eruption.
The usual pattern with Icelandic eruptions is for rising
and stretching of the surface as magma moves up to shallow depths of a few
kilometres, followed by contraction and sinking of the surface as magma
exits the shallow magma chamber and erupts at the surface.
From analysis of radar data scientist know of two events
at Eyjafjallajökull, in 1994 and 1999, that started in a similar way with
magma moving to a shallow depths (5-6 kilometres). However, in both cases
the magma then spread out laterally and remained in the crust.
At the end of the last ice age, the rate of eruption in
Iceland was some 30 times higher than recent historic rates. This is because
the reduction in the ice load reduced the pressure on the mantle, leading to
decompression melting there. Since the late 19th Century the ice caps in
Iceland have been shrinking yet further, due to changing climate. This will
lead to additional magma generation, so we should expect more frequent
and/or more voluminous eruptions in the future.
Eyjafjallajökull is a relatively small volcano and
unlikely to erupt the volumes of material that will have a significant
impact on climate. However, eruptions of Eyjafjallajökull in 1821-1823 and
1612 were followed in short shrift by eruptions of its much larger neighbour,
Katla.
Geologists have no idea when it will stop. An eruption in
Iceland in 1973 lasted more than five months.
Next week in part 2 we look at the environmental changes
and impacts.
Note: Claus Rink is a geoscientist working in
Iceland and Greenland and is also a teacher who gives lectures on
volcanology and glaciology. He is member of the Rotary Club Eastern Seaboard
and is managing an education project for underprivileged people.
