Reykjavík Grapevine - 07.05.2010, Blaðsíða 12

The Reykjavík Grapevine
Issue 05 — 2010
12
Log on to grapevine.is to see many morestunning photos of the eruption
and ashfall, and to read detailed and updated reports on all things volcano..
You are probably aware of the spec-
tacular (if small) volcanic eruption on
Fimmvörðuháls, the ridge next to Ey-
jafjallajökull glacier. We wrote about it
last issue and everything. That erup-
tion sadly ended not long after we
went to print, and even most volcanol-
ogists generally believed it was over.
But shortly after midnight on April
14th, everyone's favourite Icelandic
volcano showed us that not only had
it not finished, but it was just warm-
ing up...
Technically it's the same volcano,
just a different eruption. What prob-
ably happened is that the pathway
to the surface on Fimmvörðuháls
blocked itself up, but the pressure be-
neath needed another way out—this
time the weak point was somewhere
around the summit caldera (crater) of
the mountain. And so unlike the pre-
vious fire-fountaining flank eruption,
this time we got lava coming up from
a fissure near the top, under the Eyjaf-
jallajökull glacier itself.
Eyjafjallajökull goes
phreatomagmatic!
Fissure eruptions in open air, like
Fimmvörðuháls, tend to produce
lava fountains, lava flows and very
little ash. Sub-glacial eruptions, on
the other hand, are totally differ-
ent beasts. This eruption began with
what's called 'phreatomagmatic' ac-
tivity—water (in this case from the
melting glacier) interacting with the
hot magma near the surface. The re-
sult was a thick plume of mostly white
steam, rising between 6 and 11 kilo-
metres into the air. As the eruption
progressed, the plume became much
blacker as the glacier melted away it
could scrub less ash from the erup-
tion plume, so the ash content of the
plume increased over time. By the first
Saturday, when Grapevine took a trip
out there, the plume was like a dark
grey pillar looming over the mountain,
being blown by winds and shearing
sideways at the top (the so-called
'umbrella' region).
And all that ash had to come down
somewhere. The heavier stuff rained
down over the surrounding area, blan-
keting everything in a thick layer of
fine grey powder. The air stank of sul-
phur, and a deathly silence prevailed.
Farmers struggled to move livestock
out of the ash fall area and some are
now claiming they will never return.
The lighter stuff caused problems on
a much, much larger scale. Taken by
high-altitude winds, the fine ash was
blown all around the northern hemi-
sphere in a matter of days. With fears
of volcanic ash being sucked into jet
engines, flights all over Europe and
beyond were grounded. Air trans-
port literally shut down for a week or
more, leaving people stranded all over
the world (including, ironically, stu-
dents from my home university in the
UK, who were on a Volcanology field
course in Italy). And this will surely
have a lasting effect on air travel.
Investigations currently abound into
whether or not the decision to ground
air traffic was the right one. On a busi-
ness and political level, this certainly
isn't over.
Eyjafjallajökull goes jökulhlaup!
Aside from the ash cloud, this erup-
tion carried one other major threat—
one that we'd been fearing since day
one: jökulhlaup. Jökulhlaup are glacial
floods, a rush of water generated in
this case by the heat of a volcanic
eruption. Within 12 hours or so of the
eruption beginning, the decision was
made to break the ring road in order
to let floodwaters pass through to
the sea, hopefully without taking the
expensive bridges with them. Shortly
thereafter the floods began: torrents
of dirty water, rocks and icebergs,
flowing down from under Gígjökull
glacier and washing south towards
the sea. The scene was spectacular,
if destructive, and repeated itself a
number of times over the following
days.
Luckily for many, after a week or so
the eruption began to change. 'Strom-
bolian' activity, which takes its name
from the famous volcano in southern
Italy and not the dish akin to a rolled
pizza, began in earnest. The ash
plume shrank down, and airspace fi-
nally began to re-open. Billowing ash
and steam was largely replaced by
small explosions casting lava bombs
hundreds of meters into the air, ac-
companied by thunderous booming
sounds. As I write this, the erup-
tion continues and shows no signs
of slowing down. We could be in for
more of the same for months to come,
perhaps with a lava flow emerging
from beneath Gígjökull at some point.
what about Katla, then?
And so, to the question seemingly on
everyone's mind—“What about Kat-
la?” The answer, right now, is “Abso-
lutely nothing”. There may be signs of
a linkage between Eyjafjallajökull and
Katla, but at the moment there are no
signs of that linkage waking up. May-
be this will change in the future—who
knows—but for now you can relax safe
in the knowledge that the volcano ev-
eryone loves to hate (come on, give
poor Katla a break!) is not about to
blow up in our faces. Unless it does.
Travel | Volcanic bliss
jAMES ASHwORTH
jULIA STAPLES
Who's Laughing Now, Europe? The Eyjafjallajökull-Fimmvörðuháls eruption