Vatnajökull in the context of "Subglacial lake"

In glaciology, an ice cap is a mass of ice that covers less than 50,000 km (19,000 sq mi) of land area (usually covering a highland area). Larger ice masses covering more than 50,000 km (19,000 sq mi) are termed ice sheets.

Laki (Icelandic pronunciation: [ˈlaːcɪ] ) or Lakagígar ([ˈlaːkaˌciːɣar̥], Craters of Laki) is a volcanic fissure in the western part of Vatnajökull National Park, Iceland, not far from the volcanic fissure of Eldgjá and the small village of Kirkjubæjarklaustur. The fissure is properly referred to as Lakagígar, while Laki is a mountain that the fissure bisects. Lakagígar is part of a volcanic system centered on the volcano Grímsvötn and including the volcano Þórðarhyrna. It lies between the glaciers of Mýrdalsjökull and Vatnajökull, in an area of fissures that run in a southwest to northeast direction.

The system erupted violently over an eight-month period between June 1783 and February 1784 from the Laki fissure and the adjoining volcano Grímsvötn. It poured out an estimated 42 billion tonnes or 14 km (18×10^ cu yd) of basalt lava as well as clouds of poisonous hydrofluoric acid and sulfur dioxide compounds that contaminated the soil, leading to the death of over 50% of Iceland's livestock population, and the destruction of the vast majority of all crops. This led to a famine which then killed at least a fifth of the island's human population, although some have claimed a quarter.

Eldgjá (Icelandic pronunciation: [ˈɛltˌcauː] , "fire canyon") is a volcano and a canyon in Iceland. Eldgjá is part of the Katla volcano; it is a segment of a 40 kilometres (25 mi) long chain of volcanic craters and fissure vents that extends northeast away from Katla volcano almost to the Vatnajökull ice cap. This fissure experienced a major eruption around 939 CE, which was the largest effusive eruption in recent history. It covered about 780 square kilometres (300 sq mi) of land with 18.6 cubic kilometres (4.5 cu mi) of lava from two major lava flows.

While Icelandic records about the effects of the eruption are sparse, paleoclimate proxies and historical records from China, Europe and the Islamic world describe widespread impacts on the Northern Hemisphere's climate. The Eldgjá eruption produced a noticeable cooling of the climate, with resulting cold winters and food crises across Eurasia.

A jökulhlaup (Icelandic pronunciation: [ˈjœːkʏl̥ˌl̥œyp] pronunciation) (literally "glacial run") is a type of glacial outburst flood. It is an Icelandic term that has been adopted in glaciological terminology in many languages. It originally referred to the well-known subglacial outburst floods from Vatnajökull, Iceland, which are triggered by geothermal heating and occasionally by a volcanic subglacial eruption, but it is now used to describe any large and abrupt release of water from a subglacial or proglacial lake/reservoir.

Since jökulhlaups emerge from hydrostatically sealed lakes with floating levels far above the threshold, their peak discharge can be much larger than that of a marginal or extra-marginal lake burst. The hydrograph of a jökulhlaup from Vatnajökull typically either climbs over a period of weeks with the largest flow near the end, or it climbs much faster during the course of some hours. These patterns are suggested to reflect channel melting, and sheet flow under the front, respectively. Similar processes on a very large scale occurred during the deglaciation of North America and Europe after the last ice age (e.g., Lake Agassiz and the English Channel), and presumably at earlier times, although the geological record is not well preserved.

Austfonna is an ice cap located on Nordaustlandet in the Svalbard archipelago in Norway. Covering an area of 7,800 km, it is Europe's third-largest glacier by area and volume, after the Severny Island ice cap of Novaya Zemlya, Russia, and Vatnajökull in Iceland. The combined area of Austfonna and the Vegafonna ice cap is 8,492 km.

Austfonna has a thickness of up to 560 metres (235 meters average thickness), and is 200 km in circumference. The ice dome reaches an elevation of 783 meters above sea level.