Travel Reference
In-Depth Information
JÖKULHLAUP!
In late 1996 the devastating Grímsvötn eruption - Iceland's fourth largest of the 20th
century, after Katla in 1918, Hekla in 1947 and Surtsey in 1963 - shook southeast Iceland
and caused an awesome jökulhlaup(glacial flood) across Skeiðarársandur. The events
leading up to it are a sobering reminder of Iceland's volatile fire-and-ice combination.
On the morning of 29 September 1996, a magnitude 5.0 earthquake shook the Vatna-
jökull ice cap. Magma from a new volcano, in the Grímsvötn region beneath Vatnajökull,
had made its way through the earth's crust and into the ice, causing the eruption of a
4km-long subsurface fissure known as Gjálp. The following day the eruption burst
through the surface, ejecting a column of steam that rose 10km into the sky.
Scientists became concerned as the subglacial lake in the Grímsvötn caldera began to
fill with water from ice melted by the eruption. Initial predictions on 3 October were that
the ice would lift and the lake would spill out across Skeiðarársandur, threatening the
Ring Road and its bridges. In the hope of diverting floodwaters away from the bridges,
massive dyke-building projects were organised on Skeiðarársandur.
On 5 November, more than a month after the eruption started, the ice did lift and the
Grímsvötn reservoir drained in a massive jökulhlaup,releasing up to 3000 billion litres of
water within a few hours. The floodwaters - dragging along icebergs the size of three-
storey buildings - destroyed the 375m-long Gígjukvísl Bridge and the 900m-long
Skeiðará Bridge, both on the Skeiðarársandur. You can see video footage of the eruption
and enormous multi-tonne blocks of ice being hurled across Skeiðarársandur at the Skaf-
tafell and Höfn visitor centres.
Some of Grímsvötn's other creations include the Ásbyrgi canyon, gouged out by a cata-
clysmic flood over just a few days. In 1934 an eruption released a jökulhlaupof 40,000 cu
metres per second, which swelled the river Skeiðará to 9km in width and laid waste to
large areas of farmland.
Grímsvötn erupted again in December 1998, November 2004 and, most recently, in
May 2011, when a huge ash plume was released into the atmosphere, disrupting air traffic
(but with nowhere near the disruption caused by 2010's Eyjafjallajökull eruption). There
was no jökulhlaupon any of these three occasions.
From August 2014, scientists have been monitoring seismic activity around Bárðar-
bunga caldera, under the northwestern part of Vatnajökull. The first fissure eruptions
from this activity have been in the Holuhraun area (ie, not subglacial) but there is the pos-
sibility of an eruption occurring under ice, and a resulting jökulhlaup. Stay tuned.
