Eldgjá: Difference between revisions

Eldgjá
Eldgjá
	Canyon floor of Eldgjá
Highest point
Elevation	varies: canyon to 800 metres (2,625 ft)
Listing	List of volcanoes in Iceland
Coordinates	63°58′00″N 18°36′33″W / 63.96667°N 18.60917°W
Geography
	Eldgjá Location in Iceland
Location	Iceland
Geology
Mountain type	Fissure vents of Katla
Last eruption	939

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Eldgjá (Icelandic pronunciation: [ˈɛltˌcauː] ^ⓘ, "fire canyon") is a volcano and a canyon in Iceland. Eldgjá and the Katla volcano are part of the same volcanic system in the south of the country.

Situated between Landmannalaugar and Kirkjubæjarklaustur, Eldgjá is the largest volcanic canyon in the world, approx. 40 km long, 270 m deep and 600 m wide at its greatest.

History

It was discovered by Þorvaldur Thoroddsen in 1893.

The eruption was the largest effusive eruption basaltic eruption in historic time (800 square kilometres (310 sq mi),^[1] 18 cubic kilometres (4.3 cu mi) of magma.^[2])^[3]^[4] Evidence from tree rings in the Northern Hemisphere indicates that 940 was one of the coolest summers in 1500 years. Summer average temperatures in places as disparate as Central Europe, Scandinavia, Canada, Alaska, and Central Asia were 2 °C lower than normal.^[5]

In March 2018, a team of medieval historians and scientists from the University of Cambridge suggested that a famous medieval Icelandic poem, Vǫluspá, estimated to date from 961, was a roughly contemporary chronicle of Eldgjá's eruption in 939.^[6] The researchers suggested that the dramatic imagery of Eldgjá's eruption was purposefully invoked in order to accelerate the Christianization of Iceland.^[7]^[8]

There is a waterfall named Ófærufoss within the canyon. A natural bridge across the waterfall vanished in 1993, reportedly due to excess water from melting ice.^[9]

The northern part of Eldgjá, including Ófærufoss, and surrounding areas, have been a part of Vatnajökull National Park since 2011.^[10]

Geography and geomorphology

Eldgjá means "fire gorge"^[11] and is a reference to the fissure that makes up the volcano.^[12] It consists of an northeast-southwest trending,^[13] about 8.5 kilometres (5.3 mi) long graben with explosion craters. It is 600 metres (2,000 ft) wide, 150 metres (490 ft) deep and part of a larger 40 kilometres (25 mi) long chain of offset grabens.^[14] The lineament is subdivided into four segments from southwest to northeast (the northeasternmost segment being known as Kambagígar^[15]);^[16] the name Eldgjá is usually only applied to the 8.5 kilometres (5.3 mi) long segment^[14] in the middle of the chain, but the 939 eruption also involved other segments.^[17] The lineament extends between the Myrdalsjökull Ice Cap in the southwest across mountainous terrain and almost reaches the Vatnajökull Ice Cap to the northeast and is the longest volcanic fissure in Iceland.^[18]

Ground fractures, normal faults, pyroclastic cones and spatter ramparts make up the Eldgjá lineament;^[13] the cones have red-to-gray colours and consist of alternating layers of lava, scoria and spatter,^[12] with the scoria and spatter sometimes fused together until they resemble lava flows.^[19] There is evidence that the Eldgjá fissure existed before the 930s eruption.^[20] The Ófærufoss waterfall, a tourist attraction, lies in the main Eldgjá fissure.^[16]

The Eldgjá is part of the wider Katla volcano, which features a series of fissures including Eldgjá and a caldera covered by the Myrdalsjökull Ice Cap.^[13] To the northeast, the lineament runs 5 kilometres (3.1 mi) away from and parallel to that of the 1783-1784 CE Laki eruption fissure,^[21]^[22] which is part of the Grimsvötn volcano.^[23] There are other volcanic centres in the area, some of which had large fissure-fed eruptions during historical time.^[24]

Geology

The interaction between the Mid-Atlantic Ridge and the Iceland hotspot has given rise to the stack of volcanic rocks that forms Iceland.^[25] Volcanoes on Iceland occur in four volcanic zones; the North Volcanic Zone in northeastern Iceland, the East Volcanic Zone in the southeast, the West Volcanic Zone in the southwest and the Snaeffelsnes Volcanic Zone in the west. The first three of these form an upside-down Y structure, with each volcanic zone consisting of volcanic and tectonic lineaments that extend from north-northeast to south-southwest. These lineaments are dotted with volcanic edifices; Eldgjá lies in the East Volcanic Zone^[26] where there are no large shield volcanoes but numerous long fissures, including Laki.^[27]

Glaciation has influenced volcanic activity on Iceland, and the occurrence of large eruptions - such as the 25 cubic kilometres (6.0 cu mi) Thjorsa lava 8,600 years ago - in the early Holocene has been attributed to the unloading of the crust caused by the melting of Pleistocene ice. This process does not appear to have influenced the Eldgjá eruption however.^[26] In turn, the eruption may have altered the shape of the Katla volcano and thus modified the behaviour of its glaciers.^[28]

The rocks erupted by Eldgjá are mainly alkali basalts, which have an uniform composition and contain phenocrysts of clinopyroxene, olivine, magnetite and plagioclase.^[29] There is however a small amount of tholeiitic rocks.^[30] The composition of Katla magmas shows evidence of long-term variations that appear to reflect a long-term cycle of its magmatic system. The Eldgjá eruption appears to be the beginning of one such cycle that continues to the present-day.^[31]

10th century eruption

The Eldgjá eruption took place in the 930s but its exact date has been uncertain. Research published in 2015 indicated that it began in 939 and ended in 940^[32] but it may have continued for several years;^[18] earlier research had put its beginning during 934-938.^[22] That the Eldgjá eruption occurred at the same time as the Millennium Eruption of Changbaishan volcano in China creates ulterior confusion, as some climatic effects of the Eldgjá eruption may actually result from the Changbaishan eruption.^[33] A tephra layer at Katla originally attributed to a 1000 AD eruption is now considered to be part of the Eldgjá eruption.^[34]

The Eldgjá eruption is the largest Holocene eruption of the Katla system. It involved a 75 kilometres (47 mi) long area of the volcano, includng both the central caldera and the Eldgjá lineament.^[13] During the course of the eruption, about 16 episodes of Plinian or subplinian eruptions took place, producing plumes with heights of 15 kilometres (9.3 mi).^[22] These episodes did not occur simultaneously across the entire length of the Eldgjá; rather the eruption commenced in the caldera and propagated northeastward.^[18] Intense lava fountaining, explosive eruptions and the effusion of lava took place.^[35]

The eruption produced two fields of (mostly pahoehoe^[36]) lava flows^[17] emanating from the southern and central sectors of the Eldgjá fracture.^[37] the lava flows were channelled down river valleys and gorges and eventually reached the sea. They cover an area of 780 square kilometres (300 sq mi) and with a volume of 18.6 cubic kilometres (4.5 cu mi) constitute the largest lava flows of the last 1,100 years.^[38] The lavas buried traces of earlier eruptions^[31] and obstructed river valleys, forcing the rivers to change their course, and altered the terrain so that large parts of the plains east of Katla can no longer be reached by jokulhlaups from the volcano.^[39] Later eruptions from Laki have buried many of the northeastern Eldgjá lava flows.^[15]

About 1.3 cubic kilometres (0.31 cu mi) dense rock equivalent^[18] of mostly basaltic ejecta^[13] became 4.5 cubic kilometres (1.1 cu mi) of tephra, which was emplaced mainly south and southeast from Eldgjá.^[40] The tephra was formed through an alternation of^[18] magmatic and phreatomagmatic processes, and is more complex than common Katla tephras.^[41] External water (e.g from ice melt) did not play a major role in driving the explosivity of the eruption.^[42] Part of the eruption occurred underneath the Katla ice cap; this part also gave rise to the Kriki hyaloclastite on the eastern side of the ice cap,^[38] a product of an interaction between lava and ice.^[18] The Eldgjá eruption was accompanied by a jokulhlaups (glacier meltwater flood) but the burial of its deposits by later glacier meltwater floods and lavas make it difficult to trace its extent.^[39]

The eruption has been linked to an episode of active continental rifting in the 930s,^[22] during which the injection of magma into dykes led to deformation of the ground surface^[43] and the evacuation of magmas from the Katla magmatic system.^[44] Part of this magma entered into the Katla magma chamber, triggering the release of silicic magmas that form part of the tephra and were at least for some time erupted simultaneously with basaltic magmas.^[22]

Both tephra layers and sulfate layers linked to the Eldgjá eruption occur in Greenland, where they have been recorded from ice cores^[45] in the form of layers where the ice contains more acids.^[46] Tephra layers from the eruption have been used to date lake sediments,^[47] volcanic eruptions at Eyjafjallajökull^[48] and events in Viking Age Iceland.^[49]

Climatic impacts

Large volcanic eruptions can produce veils of aerosols in the atmosphere from sulfur dioxide, which reduce the amount of sunlight reaching Earth's surface and alter its climate.^[25] Eldgjá produced about 232000000 t of sulfur dioxide.^[13] The Eldgjá eruption is the largest volcanic atmospheric pollution event of the last few millennia.^[50]

The climate impact of the Eldgjá has been recorded in historical reports, ice cores, tree rings and other environmental records.^[23] Tree rings suggest a cooling of about 0.7–1.5 °C (1.3–2.7 °F) in the Northern Hemisphere during 940 CE, and is most pronounced in Alaska, Canadian Rocky Mountains, Central Asia, Central Europe and Scandinavia; in Canada and Central Asia it lasted until 941 CE.^[51] Volcanic aerosols often weaken the monsoons that feed the Nile River in Africa; during 939 the water levels of the river were unusually low.^[52]

Human impacts

Even though Iceland was already settled at that time, there are no contemporary historical records of the eruption although there are anecdotal reports recorded in the Book of Settlements, which was written about 200 years later^[18] and events in the poem Voluspa which may record the eruption.^[53] According to the Book of Settlements, lava flows forced settlers east of Katla off their land;^[35] farms belonging to at least two settlements in the Álftaver area southeast of Katla had to be abandoned due to damage from lava flows.^[54] Tephra covered an area of about 20,000 square kilometres (7,700 sq mi) on Iceland; of these, 600 square kilometres (230 sq mi) were covered with over 1 metre (3 ft 3 in) of tephra and had to be abandoned, while 2,600 square kilometres (1,000 sq mi) received a tephra cover exceeding 20 centimetres (7.9 in) and suffered heavy damage as a result.^[55] The events and impact of the eruption may have played a role in stimulating the Christianization of Iceland.^[56]

The settler Molda-Gnúpur took possession of land in Álftaver district between the rivers Kúðafjót and Eyjará. At that time a large lake was there and good swan hunting. He sold part of his settlement to many newcomers. The area became populated before it was overrun by jarðeldur (an earth fire), then they fled west to Höfðabrekka and set up a camp at Tjaldavellir
— Landnámabók pp. 328–331; Translation in Pálsson and Edwards 1972, Chap. 86^[57]

Unlike the local impacts on Iceland, the effects of the Eldgjá eruption on Europe appear in the historical record.^[58] Darkened skies were reported from Germany, Ireland, Italy, Portugal and Spain^[32] although the interpretation of contemporary reports as referencing atmospheric phenomena linked to the Eldgjá eruption is controversial.^[59]^[60] Food crises reported in China and Western Europe at that time have been linked to the Eldgjá eruption.^[11]

Impacts of a repeat

Large fissure-fed effusive eruptions in Iceland reoccur every few centuries. The much smaller (0.27±0.07 km³) 2010 eruption of Eyjafjallajökull caused worldwide disruptions of air travel, with economic losses of over 1,000,000,000$ for airlines alone,^[24] because volcanic ash can interfere with the operation of airplane engines. Additional hazards of a widespread aerosol layer are its corrosive effects on equipment, decreased visibility leading to accidents on the sea, as well as health hazards resulting from the aerosols. The impact could extend to North Africa.^[61]

References

^ Árni Hjartarson 2011. Víðáttumestu hraun Íslands. (The Largest Lavas of Iceland). Náttúrufræðingurinn 81, 37-49.
^ "Katla: Eruptive History". Global Volcanism Program. Smithsonian Institution.
^ Albert Zijlstra (29 September 2016). "Eldgja: Eruption dating". Retrieved 1 January 2017.
^ Oppenheime, Clive; et al. (19 March 2018). "The Eldgjá eruption: timing, long-range impacts and influence on the Christianisation of Iceland". Climatic Change. 147 (3–4): 369–381. doi:10.1007/s10584-018-2171-9. PMC 6560931. PMID 31258223.
^ "Volcanic eruption influenced Iceland's conversion to Christianity". ScienceDaily. Retrieved 2018-03-30.
^ "10th century Eldgjá eruption thought to have influenced Christianisation of Iceland". Retrieved 2018-03-30.
^ Kettley, Sebastian (2018-03-21). "Iceland volcano ERUPTION: Scientists make shock discovery about Eldgja volcanic apocalypse". Express.co.uk. Retrieved 2018-03-30.
^ Dockrill, Peter. "A Volcanic Explosion 1,000 Years Ago Was So Brutal, It Slayed Icelandic Gods". ScienceAlert. Retrieved 2018-03-30.
^ Review, Iceland (2007-08-28). "Can you tell me what happened to the natural stone bridge over Ófaerufoss at Eldgjá?". Iceland Review. Retrieved 2018-03-30.
^ "Ósnortin víðerni og einstakar jarðmyndanir" (in Icelandic). Ministry for the Environment and Natural Resources. 29 July 2011. Retrieved 24 March 2014.
^ ^a ^b Oppenheimer et al. 2018, p. 370.
^ ^a ^b Miller 1989, p. 8.
^ ^a ^b ^c ^d ^e ^f Brugnatelli & Tibaldi 2020, p. 2.
^ ^a ^b Gudmundsson 2016, p. 90.
^ ^a ^b Miller 1989, p. 13.
^ ^a ^b Miller 1989, p. 12.
^ ^a ^b Larsen 2010, p. 37.
^ ^a ^b ^c ^d ^e ^f ^g Moreland et al. 2019, p. 130.
^ Miller 1989, p. 10.
^ Miller 1989, p. 14.
^ Miller 1989, p. 7.
^ ^a ^b ^c ^d ^e Brugnatelli & Tibaldi 2020, p. 3.
^ ^a ^b Brugnatelli & Tibaldi 2020, p. 4.
^ ^a ^b Brugnatelli & Tibaldi 2020, p. 10.
^ ^a ^b Brugnatelli & Tibaldi 2020, p. 1.
^ ^a ^b Gudmundsson 2016, p. 79.
^ Gudmundsson 2016, p. 91.
^ Larsen 2010, p. 40.
^ Thordarson et al. 2001, p. 38.
^ Thordarson et al. 2001, p. 41.
^ ^a ^b Óladóttir, Sigmarsson & Larsen 2018, p. 3.
^ ^a ^b Simpson 2020, p. 23.
^ Yin et al. 2012, p. 157.
^ Larsen 2010, p. 30.
^ ^a ^b Thordarson et al. 2001, p. 35.
^ Self, Keszthelyi & Thordarson 1998, p. 82.
^ Moreland et al. 2019, p. 131.
^ ^a ^b Larsen 2010, p. 38.
^ ^a ^b Larsen 2010, p. 44.
^ Guðmundsdóttir, Eiríksson & Larsen 2012, p. 65.
^ Larsen 2010, p. 28.
^ Moreland et al. 2019, p. 147.
^ Acocella & Trippanera 2016, p. 872.
^ Óladóttir, Sigmarsson & Larsen 2018, p. 10.
^ Oppenheimer et al. 2018, p. 372.
^ Hammer 1980, pp. 368–369.
^ Brader et al. 2017, p. 121.
^ Dugmore et al. 2013, p. 239.
^ Swindles et al. 2019, p. 212.
^ Martini & Chesworth 2011, p. 285.
^ Oppenheimer et al. 2018, p. 374.
^ Oppenheimer et al. 2018, p. 376.
^ Oppenheimer et al. 2018, p. 377.
^ Larsen 2010, p. 27.
^ Larsen 2010, p. 43.
^ Oppenheimer et al. 2018, p. 378.
^ Martini & Chesworth 2011, p. 288.
^ Ebert 2019, p. 1.
^ Brugnatelli & Tibaldi 2021, p. 3.
^ Ebert 2019, p. 2.
^ Brugnatelli & Tibaldi 2020, p. 11.

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Brugnatelli, Vermondo; Tibaldi, Alessandro (22 October 2020). "Effects in North Africa of the 934–940 CE Eldgjá and 1783–1784 CE Laki eruptions (Iceland) revealed by previously unrecognized written sources". Bulletin of Volcanology. 82 (11): 73. doi:10.1007/s00445-020-01409-0. ISSN 1432-0819.
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External links

[1] Árni Hjartarson 2011. Víðáttumestu hraun Íslands. (The Largest Lavas of Iceland). Náttúrufræðingurinn 81, 37-49.

[gvp-history-2] "Katla: Eruptive History". Global Volcanism Program. Smithsonian Institution.

[3] Albert Zijlstra (29 September 2016). "Eldgja: Eruption dating". Retrieved 1 January 2017.

[4] Oppenheime, Clive; et al. (19 March 2018). "The Eldgjá eruption: timing, long-range impacts and influence on the Christianisation of Iceland". Climatic Change. 147 (3–4): 369–381. doi:10.1007/s10584-018-2171-9. PMC 6560931. PMID 31258223.

[5] "Volcanic eruption influenced Iceland's conversion to Christianity". ScienceDaily. Retrieved 2018-03-30.

[6] "10th century Eldgjá eruption thought to have influenced Christianisation of Iceland". Retrieved 2018-03-30.

[7] Kettley, Sebastian (2018-03-21). "Iceland volcano ERUPTION: Scientists make shock discovery about Eldgja volcanic apocalypse". Express.co.uk. Retrieved 2018-03-30.

[8] Dockrill, Peter. "A Volcanic Explosion 1,000 Years Ago Was So Brutal, It Slayed Icelandic Gods". ScienceAlert. Retrieved 2018-03-30.

[9] Review, Iceland (2007-08-28). "Can you tell me what happened to the natural stone bridge over Ófaerufoss at Eldgjá?". Iceland Review. Retrieved 2018-03-30.

[10] "Ósnortin víðerni og einstakar jarðmyndanir" (in Icelandic). Ministry for the Environment and Natural Resources. 29 July 2011. Retrieved 24 March 2014.

[FOOTNOTEOppenheimerOrchardStoffelNewfield2018370-11] Oppenheimer et al. 2018, p. 370.

[FOOTNOTEMiller19898-12] Miller 1989, p. 8.

[FOOTNOTEBrugnatelliTibaldi20202-13] ^ ^a ^b ^c ^d ^e ^f Brugnatelli & Tibaldi 2020, p. 2.

[FOOTNOTEGudmundsson201690-14] Gudmundsson 2016, p. 90.

[FOOTNOTEMiller198913-15] Miller 1989, p. 13.

[FOOTNOTEMiller198912-16] Miller 1989, p. 12.

[FOOTNOTELarsen201037-17] Larsen 2010, p. 37.

[FOOTNOTEMorelandThordarsonHoughtonLarsen2019130-18] ^ ^a ^b ^c ^d ^e ^f ^g Moreland et al. 2019, p. 130.

[FOOTNOTEMiller198910-19] Miller 1989, p. 10.

[FOOTNOTEMiller198914-20] Miller 1989, p. 14.

[FOOTNOTEMiller19897-21] Miller 1989, p. 7.

[FOOTNOTEBrugnatelliTibaldi20203-22] Brugnatelli & Tibaldi 2020, p. 3.

[FOOTNOTEBrugnatelliTibaldi20204-23] Brugnatelli & Tibaldi 2020, p. 4.

[FOOTNOTEBrugnatelliTibaldi202010-24] Brugnatelli & Tibaldi 2020, p. 10.

[FOOTNOTEBrugnatelliTibaldi20201-25] Brugnatelli & Tibaldi 2020, p. 1.

[FOOTNOTEGudmundsson201679-26] Gudmundsson 2016, p. 79.

[FOOTNOTEGudmundsson201691-27] Gudmundsson 2016, p. 91.

[FOOTNOTELarsen201040-28] Larsen 2010, p. 40.

[FOOTNOTEThordarsonMillerLarsenSelf200138-29] Thordarson et al. 2001, p. 38.

[FOOTNOTEThordarsonMillerLarsenSelf200141-30] Thordarson et al. 2001, p. 41.

[FOOTNOTEÓladóttirSigmarssonLarsen20183-31] Óladóttir, Sigmarsson & Larsen 2018, p. 3.

[FOOTNOTESimpson202023-32] Simpson 2020, p. 23.

[FOOTNOTEYinJullBurrZheng2012157-33] Yin et al. 2012, p. 157.

[FOOTNOTELarsen201030-34] Larsen 2010, p. 30.

[FOOTNOTEThordarsonMillerLarsenSelf200135-35] Thordarson et al. 2001, p. 35.

[FOOTNOTESelfKeszthelyiThordarson199882-36] Self, Keszthelyi & Thordarson 1998, p. 82.

[FOOTNOTEMorelandThordarsonHoughtonLarsen2019131-37] Moreland et al. 2019, p. 131.

[FOOTNOTELarsen201038-38] Larsen 2010, p. 38.

[FOOTNOTELarsen201044-39] Larsen 2010, p. 44.

[FOOTNOTEGuðmundsdóttirEiríkssonLarsen201265-40] Guðmundsdóttir, Eiríksson & Larsen 2012, p. 65.

[FOOTNOTELarsen201028-41] Larsen 2010, p. 28.

[FOOTNOTEMorelandThordarsonHoughtonLarsen2019147-42] Moreland et al. 2019, p. 147.

[FOOTNOTEAcocellaTrippanera2016872-43] Acocella & Trippanera 2016, p. 872.

[FOOTNOTEÓladóttirSigmarssonLarsen201810-44] Óladóttir, Sigmarsson & Larsen 2018, p. 10.

[FOOTNOTEOppenheimerOrchardStoffelNewfield2018372-45] Oppenheimer et al. 2018, p. 372.

[FOOTNOTEHammer1980368–369-46] Hammer 1980, pp. 368–369.

[FOOTNOTEBraderLloydBarlowNorðdahl2017121-47] Brader et al. 2017, p. 121.

[FOOTNOTEDugmoreNewtonSmithMairs2013239-48] Dugmore et al. 2013, p. 239.

[FOOTNOTESwindlesOutramBattHamilton2019212-49] Swindles et al. 2019, p. 212.

[FOOTNOTEMartiniChesworth2011285-50] Martini & Chesworth 2011, p. 285.

[FOOTNOTEOppenheimerOrchardStoffelNewfield2018374-51] Oppenheimer et al. 2018, p. 374.

[FOOTNOTEOppenheimerOrchardStoffelNewfield2018376-52] Oppenheimer et al. 2018, p. 376.

[FOOTNOTEOppenheimerOrchardStoffelNewfield2018377-53] Oppenheimer et al. 2018, p. 377.

[FOOTNOTELarsen201027-54] Larsen 2010, p. 27.

[FOOTNOTELarsen201043-55] Larsen 2010, p. 43.

[FOOTNOTEOppenheimerOrchardStoffelNewfield2018378-56] Oppenheimer et al. 2018, p. 378.

[FOOTNOTEMartiniChesworth2011288-57] Martini & Chesworth 2011, p. 288.

[FOOTNOTEEbert20191-58] Ebert 2019, p. 1.

[FOOTNOTEBrugnatelliTibaldi20213-59] Brugnatelli & Tibaldi 2021, p. 3.

[FOOTNOTEEbert20192-60] Ebert 2019, p. 2.

[FOOTNOTEBrugnatelliTibaldi202011-61] Brugnatelli & Tibaldi 2020, p. 11.

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@@ Line 64: / Line 64: @@
 === Climatic impacts ===
-Large volcanic eruptions can produce veils of [[aerosol]]s in the atmosphere from [[sulfur dioxide]], which reduce the amount of sunlight reaching Earth's surface and alter its climate.{{sfn|Brugnatelli|Tibaldi|2020|p=1}} Eldgjá produced about {{val|232000000|ul=t}} of sulfur dioxide.{{sfn|Brugnatelli|Tibaldi|2020|p=2}}
+Large volcanic eruptions can produce veils of [[aerosol]]s in the atmosphere from [[sulfur dioxide]], which reduce the amount of sunlight reaching Earth's surface and alter its climate.{{sfn|Brugnatelli|Tibaldi|2020|p=1}} Eldgjá produced about {{val|232000000|ul=t}} of sulfur dioxide.{{sfn|Brugnatelli|Tibaldi|2020|p=2}} The Eldgjá eruption is the largest volcanic [[atmospheric pollution]] event of the last few millennia.{{sfn|Martini|Chesworth|2011|p=285}}
 The climate impact of the Eldgjá has been recorded in historical reports, [[ice core]]s, [[tree ring]]s and other environmental records.{{sfn|Brugnatelli|Tibaldi|2020|p=4}} [[Tree ring]]s suggest a cooling of about {{convert|0.7|-|1.5|C-change}} in the [[Northern Hemisphere]] during 940 [[Common Era|CE]], and is most pronounced in Alaska, Canadian [[Rocky Mountains]], Central Asia, Central Europe and Scandinavia; in Canada and Central Asia it lasted until 941 CE.{{sfn|Oppenheimer|Orchard|Stoffel|Newfield|2018|p=374}} Volcanic aerosols often weaken the [[monsoon]]s that feed the [[Nile River]] in Africa; during 939 the water levels of the river were unusually low.{{sfn|Oppenheimer|Orchard|Stoffel|Newfield|2018|p=376}}
@@ Line 71: / Line 71: @@
 Even though Iceland was already settled at that time, there are no contemporary historical records of the eruption although there are anecdotal reports recorded in the [[Book of Settlements]], which was written about 200 years later{{sfn|Moreland|Thordarson|Houghton|Larsen|2019|p=130}} and events<!--Quote?--> in the poem [[Voluspa]] which may record the eruption.{{sfn|Oppenheimer|Orchard|Stoffel|Newfield|2018|p=377}} According to the Book of Settlements, lava flows forced settlers east of Katla off their land;{{sfn|Thordarson|Miller|Larsen|Self|2001|p=35}} farms belonging to at least two settlements in the Álftaver area southeast of Katla had to be abandoned due to damage from lava flows.{{sfn|Larsen|2010|p=27}} Tephra covered an area of about {{convert|20000|km2}} on Iceland; of these, {{convert|600|km2}} were covered with over {{convert|1|m}} of tephra and had to be abandoned, while {{convert|2600|km2}} received a tephra cover exceeding {{convert|20|cm}} and suffered heavy damage as a result.{{sfn|Larsen|2010|p=43}} The events and impact of the eruption may have played a role in stimulating the [[Christianization of Iceland]].{{sfn|Oppenheimer|Orchard|Stoffel|Newfield|2018|p=378}}
+{{blockquote|text=The settler Molda-Gnúpur took possession of land in Álftaver district between the rivers Kúðafjót and Eyjará. At that time a large lake was there and good swan hunting. He sold part of his settlement to many newcomers. The area became populated before it was overrun by jarðeldur (an earth fire), then they fled west to Höfðabrekka and set up a camp at Tjaldavellir|source=Landnámabók pp. 328–331; Translation in Pálsson and Edwards 1972, Chap. 86{{sfn|Martini|Chesworth|2011|p=288}}}}
 Unlike the local impacts on Iceland, the effects of the Eldgjá eruption on Europe appear in the historical record.{{sfn|Ebert|2019|p=1}} Darkened skies were reported from Germany, Ireland, Italy, Portugal and Spain{{sfn|Simpson|2020|p=23}} although the interpretation of contemporary reports as referencing atmospheric phenomena linked to the Eldgjá eruption is controversial.{{sfn|Brugnatelli|Tibaldi|2021|p=3}}{{sfn|Ebert|2019|p=2}}<!--Mention examples? {{sfn|Oppenheimer|Orchard|Stoffel|Newfield|2018|p=376}}--> Food crises reported in China and Western Europe at that time have been linked to the Eldgjá eruption.{{sfn|Oppenheimer|Orchard|Stoffel|Newfield|2018|p=370}}
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 * {{cite journal |last1=Hammer |first1=C. U. |title=Acidity of Polar Ice Cores in Relation to Absolute Dating, Past Volcanism, and Radio–Echoes |journal=Journal of Glaciology |date=1980 |volume=25 |issue=93 |pages=359–372 |doi=10.3189/S0022143000015227 |url=https://www.cambridge.org/core/journals/journal-of-glaciology/article/acidity-of-polar-ice-cores-in-relation-to-absolute-dating-past-volcanism-and-radioechoes/44073EE8AF12069C4ADBAE84032849B9 |language=en |issn=0022-1430}}
 * {{cite journal |last1=Larsen |first1=Guðrún |title=3 Katla: Tephrochronology and Eruption History |journal=Developments in Quaternary Sciences |date=1 January 2010 |volume=13 |pages=23–49 |url=https://www.sciencedirect.com/science/article/pii/S1571086609013037 |publisher=Elsevier |language=en}}
+* {{Cite book |url=http://link.springer.com/10.1007/978-90-481-9413-1 |title=Landscapes and Societies |date=2011 |publisher=Springer Netherlands |isbn=978-90-481-9412-4 |editor-last=Martini |editor-first=I. Peter |location=Dordrecht |language=en |doi=10.1007/978-90-481-9413-1 |editor-last2=Chesworth |editor-first2=Ward}}
 * {{cite report|last=Miller|first=Jay|title=The 10th century eruption of Eldgjá, southern Iceland|volume=8903|publisher=Nordic Volcanological Institute, University of Iceland|year=1989|url=https://nordvulk.hi.is/sites/nordvulk.hi.is/files/NVI_Reports_pdf/nvi_report_8903_low_text.pdf}}
 * {{cite journal |last1=Moreland |first1=William Michael |last2=Thordarson |first2=Thor |last3=Houghton |first3=Bruce F. |last4=Larsen |first4=Gudrún |title=Driving mechanisms of subaerial and subglacial explosive episodes during the 10th century Eldgjá fissure eruption, southern Iceland |journal=Volcanica |date=28 August 2019 |volume=2 |issue=2 |pages=129–150 |doi=10.30909/vol.02.02.129150 |url=http://jvolcanica.org/ojs/index.php/volcanica/article/view/31 |language=en |issn=2610-3540}}