Vatnajökull:
Area: Approx. 8.300 km2
Highest point (excl. Öræfajokull): 2000m
Thickness: Estim. av. 420 - 450m, Max 900m
Type: Ice cap
THE MIGHTY VATNAJÖKULL occupies vast highlands in the Southeast
comprising 8,300 square kilometres. The western half lies within
the active volcanic zone and its southern margin is fringed by
high mountains, cut by numerous valleys. There, the most prominent
mountain is the Öræfajölull volcano (chapter 7). At the northern
margin, another high volcano towers over the ice cap: Kverkfjöll
(1,920 m) with its two calderas and a powerful, partly glaciated,
geothermal area.
Within the ice cap lie at least
four other active central volcanoes, including the Bárðarbunga
volcano (2,000 m), and the Grímsvötn volcano (1,719 m), both set
with deep ice-filled calderas. Grímsvötn is a very powerful
geothermal area and the caldera holds a warm subglacial lake. Its
water level rises due to ice melting until the lake is partly
emptied in a glacier outburst flood (jökulhlaup). These huge,
periodical floods enter glacial rivers with a discharge of
3,000-8,000 cubic metres per second. Jökulhlaups accompanying
volcanic eruptions have a still larger discharge, up to 40,000
cubic metres per second
.Nunataks like Grendill (1,570 m) and Goðahnúkar in the east and
Pálsfjall (1,335 m) in the west break up the almost 150-km-long
and 50 to 100-km-wide white expanses. Two larger massifs, Esjufjöll
and Mávabyggðir, also rise high above the ice as islands from a
frozen sea. A few glacier domes attain an elevation of up to 1,700
m but most of the ice fields lie at 1,100-1,500 m above sea level.
Some 23 named outlet glaciers flow from the accumulation area.
Öræfajokull is connected to Vatnajokull but identified as a
separate glacier system. It feeds additional 9 named outlet
glaciers.Many Vatnajokull outlet glaciers, especially in the west
and north are flat, broad ice lopes and many of them are of the
surging type. Other glaciers include ice falls up to 800-1,000 m
high. Many ice-dammed and proglacial lakes exist at the ice cap
margins. Grænalón is the largest ice-dammed lake and Jökulsárlón
the largest proglacial lake. Jökulsárlón is bordered by a
retreating glacier which fills a 20-km-long overdeepened trench
and calves into the lake. A new fjord would be created if the sea
were to break through a small barrier in front of the lake.The
Englishman W.L. Watts and his Icelandic escorts became the first
men to cross Vatnajokull in recent times (1875). Its highest dome
(Bárðarbunga, 2000 m) was climbed in 1935 by an Austrian-Italian
expedition.
Today, researchers, mountaineers and travellers roam the white,
slow-moving ice ocean and four huts have been built on its rocky
outcrops. Radio-echo depth soundings have been aimed at Vatnajökul
for years and, slowly, a complete picture of the underlying land
is emerging. The ice is generally 300-500 metres deep, ranging in
many places to 600-700 metres, with the maximum thickness about 900
metres. An estimated average thickness of 450 metres would render
a total ice volume of almost 4000 cubic kilometres. Other types of
research are also carried out such as mass balance and movement
studies, chemical research and studies of surges. There are ample
opportunities for both laymen and scientists to study nature at
Vatnajokull. The ice cap is a world of its own.
From: Ari Trausti Guðmundsson, Ragnar Th. Sigurðsson. Light on
Ice - Glaciers in Iceland. p. 44-45. Ormstunga 1995
(www.ormstunga.is).