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The Iceland and Arctic Ocean Region
The volcano-rich island of Iceland has the land area of the state of Virginia with only 4% of its population. Iceland's population of 301,000 ranks it above only the Kurils and Antarctica, among CAVW regions, but it enjoys the highest literacy rate (100%) of any nation in the world, and its close interaction with volcanoes makes it indeed a nation of volcanologists. Iceland has the highest proportion of Holocene volcanoes that bear dated eruptions (86%), and this follows largely from work initiated by Iceland's pioneer of tephrochronology, Sigurdur Thorarinsson, who developed this stratigraphic dating technique and assigned its name. Iceland leads all regions with nearly half of its eruptions having been dated by this approach, and detailed studies of the products of Icelandic eruptions are ongoing and will modify the eruptive record shown here.
First settled by Vikings in the 9th century AD, Iceland established its own parliament in 930 and recorded its first historical eruption only a few years later. An eruption in 1000 AD played an important role in Icelandic history when it occurred during a debate over the national religion at a meeting of the Icelandic outdoor parliament at Thingvellier. After a golden age of literature in the 12th and 13th centuries, natural history reporting reached a low around the 15th century (only 5 historical eruptions recorded, as opposed to 12 each in the 12th and 13th centuries and 15 in the 17th century). In the years 1707-09 a third of the population died from smallpox, and the 1783-84 Laki eruption killed a fifth of the remaining population by famine. Iceland gained sovereignty from Denmark in 1918 and complete independence in 1944.
This land of fire and ice is noted for subglacial and regional fissure eruptions, having produced 89% and 43% (respectively) of the world's total for each type. Fissure eruptions dominate because Iceland combines a hotspot setting with one of the few places where the oceanic rift system emerges above sea level. This setting has brought widespread attention to the region's volcanoes from many geophysical sub-disciplines. Following the 1974-84 fissure eruptions at Krafla caldera, Iceland has been relatively quiet, with eruptions from Hekla in 1991 and 2000 and subglacial eruptions from Grímsvötn caldera in 1996, 1998, and 2004. Further to the north, Jan Mayen erupted in 1986, and in 1999 a seismic swarm on the East Gakkel Ridge (near 86°N, 85°E) may have originated from submarine lava effusion, although this has not been confirmed.
Iceland's volcanoes have been organized by volcanic systems that provide meaningful grouping of genetically related surface features. We have followed the volcanic systems used in the tectonics sheet of the geological map of Iceland (Johannesson and Saemundsson, 1998). The en echelon distribution of volcanic systems along the subaerial component of the Mid-Atlantic Ridge has resulted in the construction of central volcanoes with long regional fissure systems, both of which are sometimes simultaneously active. The length of the fissures often exceeds the mid-point of the distance between adjacent central volcanoes, so that closely spaced eruptive fissures may actually be related to volcanic systems whose centers lie in opposite directions. Two of the largest recent eruptions in Iceland, the Eldgjá eruption about 934 AD and the 1783 Laki eruption, took place from fissures only about 5 km apart that parallel each other for several tens of kilometers, but are related to the Katla and Grímsvötn central volcanoes, respectively, whose summits lie 120 km apart.
The CAVW organizers did not recognize arctic volcanism and assigned no region numbers beyond 19, so we consequently have expanded region 17 beyond Jan Mayen to include the full Arctic Ocean and adjacent northern seas, thus including Pleistocene volcanism on Spitsbergen (north of Norway), and submarine rifts such as the East Gakkel Ridge.
List of Holocene volcanoes in the Iceland and Arctic Ocean region.