Largest
glacier in Europe---this is
just a sliver of it spilling
out into a valley
As fall marches
toward winter in the Northern
Hemisphere, Iceland’s rugged
terrain casts long shadows back
on itself, exaggerating the topography
of the island's snow-covered mountains,
particularly along the eastern
coast. On the northeastern portion
of the island’s largest
ice cap—Vatnajokull—what
appears to be another of the season’s
long shadows is actually a layer
of ash from the recent eruption
of the sub-glacial volcano that
lies beneath the thick ice.
The Grimsvötn
Volcano and Vatnajökull engage
in a cycle of creation and destruction,
build-up and release. Beneath
a sheet of ice 200 meters thick
in places, Grimsvötn simmers,
its crater filled with a lake
of meltwater dammed by ice blockages.
The immense mass of water and
ice presses down on the volcano,
holding explosive eruptions in
check. As the bottom of the glacier
continues to melt, the lake eventually
overruns the level of the ice
dams, releasing a glacial outburst
flood. The draining of the lake
temporarily releases the pressure
on the volcano, which may make
explosive eruptions more likely.
Ash from Grimsvotn
Volcano on Iceland's Vatnajokull[2]
In mid-October,
the lake spilled over the caldera’s
ice dams, and on November 2, 2004,
Grimsv?tn spewed a large plume
of ash and steam high into the
atmosphere. The plume forced air
traffic to be re-routed and left
a dark blanket across the northern
part of the scalloped glacier.
This Moderate Resolution Imaging
Spectroradiometer (MODIS) image
captured by the sensor on the
Terra satellite shows the sooty
remains of the eruption spread
across the glacier. Soon, the
evidence of the eruption will
be frozen in time, as the layer
of ash is buried by the advancing
winter’s snows. [2]
Vatnajökull
is the largest glacier in Iceland.
It is located in the south-east
of the island, covering more than
8% of the country. With a size
of 8,100 km², it is the largest
glacier in Europe in volume (3,100
km³) and the second largest
(after Austfonna on Nordaustlandet,
Svalbard) in area (not counting
the still larger ice cap of Severny
Island of Novaya Zemlya, Russia,
which is located in the extreme
northeast of Europe).
The average thickness of
the ice is 400 m, with a maximum
thickness of 1,000 m. Iceland's
highest peak, Hvannadalshnúkur
(2,110 m), is located in the
southern periphery of Vatnajökull,
near Skaftafell National Park.
It is classified as an ice cap
glacier.
Under the glacier, as under
many of the glaciers of Iceland,
there are several volcanoes.
The volcanic lakes, Grímsvötn
for example, were the sources
of a large glacial lake outburst
flood in 1996. The volcano under
these lakes also caused a considerable
but short-time eruption in the
beginning of November 2004.
During the last ice age, numerous
volcanic eruptions occurred
under Vatnajökull, creating
many subglacial eruptions. These
eruptions formed tuyas, such
as Herðubreið which
originally sat beneath Vatnajökull
during the last ice age.[4]
28th
of April 2006. Elli, the only
licenced commercial pilot in
Team Moby, took Baldur and Einar
flying over Europe's largest
glacier on a sunny day (anything
to kill time...).
The big hole you see at about
0.50 into the video is where
the surface has plummited down
after a small volcanic eruption
underneath the glacier. The
hole is big enough to swallow
a small village.
...Oh, and the
Mayday thing at the end is just
a joke. by undarlegt
Vatnajökull has been shrinking
for some years now, possibly
because of climatic changes
and recent volcanic activity.
Until 1930 it was growing. The
phenomenon of Jökulhlaup
is at present time confined
to Vatnajökull.
According to Guinness World
Records Vatnajökull is
the object of the world's longest
sight line, 550 km from Slættaratindur,
the highest mountain in the
Faroe Islands. GWR state that
"owing to the light bending
effects of atmospheric refraction,
Vatnajökull (2119m), Iceland,
can sometimes be seen from the
Faroe Islands, 340 miles (550km)
away". This may be based
on a claimed sighting by a British
sailor in 1939. The validity
of this record is analysed/undermined
in mathematical and atmospheric
detail by J.C. Ferranti.[4]
Grímsvötn
The Grímsvötn lakes (Icelandic:
vötn, singular: vatn) are lakes
in Iceland. They lie in the highlands
of Iceland at the northwestern side
of the Vatnajökull glacier and
are covered by its ice cap. Beneath
them is a large magma chamber of a
powerful volcano. The location of
the lakes is 64°25'N 17°20'W?
/ ?64.417°N 17.333°W? / 64.417;
-17.333, at an elevation of 1,725
m (5,659 ft).
Grímsvötn
has a southwest-northeast-trending fissure
system, and the massive climate-impacting
Laki fissure eruption of 1783-1784 was
a part of the same fissure system. Grímsvötn
was erupting at the same time as Laki
during 1783, but continued to erupt
until 1785. Because most of the volcano
lies underneath Vatnajökull, most
of its eruptions have been subglacial.[5]
