The Vatnajökull glacier in Europe is a temperate glacier covering about 8300 km2 in the SE part of Iceland. Volcanic fissure systems of the Mid- Atlantic Ridge plate boundary are partly covered by the western part of the ice sheet. Two major volcanic centers lie beneath the ice, the Bardarbunga volcanic center and the Grimsvotn volcanic center both with large subglacial caldera depressions. The Bardarbunga center is a part of a fissure system extending over 100 km to the south and some 50 km to the north of the glacier. The last eruption within the Bardarbunga center occurred in 1910, but eruptions on the fissure system have occurred in 871 AD, 1477 AD and 1862 AD, all producing substantial amounts of lava.
The Grimsvotn center is the more active of the two with an eruption frequency during past centuries close to one eruption per decade. The last eruption occurred in 1983. As Bardarbunga the Grimsvotn center is a part of a a fissure system which includes the Laki fissure, which in 1783 produced about 12-14 km3 of basaltic lava. Within the ice filled Grimsvotn caldera intense geothermal activity continuously melts the ice to form a subglacial lake, which at intervals of 5 to 10 years is emptied along subglacial channels to create large floods (jökulhlaup) on the sandur plain, Skeidararsandur, on the Icelandic south coast. The lake was last emptied in 1996.
Karl Grönvold and Haukur Jóhannesson, 1984:
Eruption in Grímsvötn 1983, course of events and
Magnús T. Gudmunsson, Freysteinn Sigmundsson and Helgi Björnsson, 1997: Ice-volcano interaction of the 1996 Gjálp subglacial eruption, Vatnajökull, Iceland. Nature, vol. 389, 954-957.
Páll Einarsson, Bryndís Brandsdóttir
Magnús Tumi Gudmunsson, Helgi Björnsson, Karl Grönvold