Editing Hekla (section)

===1104 to 1878 ===<!---could this section better be handled in a table--->
;1104 (H1)
[[File:Stöng Viking Longhouse.jpg|thumb|right|Main building of the replica of [[Þjóðveldisbærinn Stöng|Stöng]], which was buried under volcanic ash from the 1104 eruption]]
Hekla had been dormant for at least 250&nbsp;years when it erupted explosively in 1104 (probably in the autumn), covering {{convert|55000|km2|abbr=on}} which is over half of Iceland with 1.2&nbsp;km<sup>3</sup><ref name="HANVp11" /> / 2.5&nbsp;km<sup>3</sup><ref name="UoI_Hekla">{{cite web|url=http://www.earthice.hi.is/page/ies_hekla |title=Hekla Volcano |access-date=14 January 2008 |work=University of Iceland, Institute of Earth Sciences |url-status=dead |archive-url=https://web.archive.org/web/20070212095558/http://www.earthice.hi.is/page/ies_hekla |archive-date=12 February 2007 }}</ref> of [[Rhyodacite|rhyodacitic]] tephra. This was the second largest tephra eruption in the country in historical times with a VEI of 5. Farms upwind of the volcano {{convert|15|km|abbr=on}} in [[Þjórsárdalur]] valley, {{convert|50|km|abbr=on}} at Hrunamannaafréttur and {{convert|70|km|abbr=on}} at Lake [[Hvítárvatn]] were abandoned because of the damage. The eruption caused Hekla to become famous throughout Europe.<ref name="GVPHEH" /><ref name="HANVp11">Thorarinsson, p. 11</ref>

;1158
A VEI-4 eruption began on 19 January 1158 producing over {{convert|0.15|km3|abbr=on}} of [[lava]] and {{convert|0.2|km3|abbr=on}} of tephra. It is likely to be the source of the ''Efrahvolshraun'' lava on Hekla's west.<ref name="GVP" /><ref name="HANVp11" />

;1206
The VEI-3 eruption began on 4 December.

;1222
The VEI-2 eruption and the 1206 eruption distributed around {{convert|0.24|km3|abbr=on}} of tephra mainly to the northeast.<ref name="GVP" /><ref>Thorarinsson, p. 12</ref>

;1300–1301
[[File:Hekla and horse.jpg|thumb|right|Hekla in 2006 and an [[Icelandic horse]]]]
This VEI-4 eruption, which started on 11 July and lasted for a year, was the second largest tephra eruption of Hekla since Iceland was settled, covering {{convert|30000|km2|abbr=on}}
of land with {{convert|0.31|km3|abbr=on}} of tephra. Over {{convert|0.5|km3|abbr=on}} of lava was also expelled. The tephra caused significant damage to the settlements of [[Skagafjörður]] and [[Fljót]], leading to over 500&nbsp;deaths that winter.<ref name="GVP" /><ref name="HANVp14">Thorarinsson, p. 14</ref>
The material output from this eruption had SiO<sub>2</sub> levels of between 56% and 64%, and apart from a slight abundance of [[olivine]] the lava, was typical of Hekla eruptions.<ref name="GSA">{{cite conference| first = Swarr| last = Gretchen| author2 = Peter Oswald| author3 = Karen Harpp| author4 = Dennis Geist| date = 27–29 March 2008| title = THE 1300 AD ERUPTION OF HEKLA VOLCANO, ICELAND| conference = Northeastern Section, Geological Society of America, 43rd Annual Meeting| location = Buffalo| url = http://gsa.confex.com/gsa/2008NE/finalprogram/abstract_134610.htm| access-date = 17 August 2008| archive-date = 14 September 2017| archive-url = https://web.archive.org/web/20170914081538/https://gsa.confex.com/gsa/2008NE/finalprogram/abstract_134610.htm| url-status = dead}}</ref>

;1341
A small eruption (VEI-3) started on 19 May and deposited around {{convert|5E7|km3|abbr=on}} of tephra over the areas west and southwest of Hekla, leading to many cattle deaths, probably mainly from [[Skeletal fluorosis|fluorosis]].<ref name="GVP" /><ref name="HANVp14" />

;1389
In late 1389 Hekla erupted again (VEI-3), starting with a large ejection of tephra to the southeast. Later "the eruption fissure moved itself out of the mountain proper and into the woods a little above Skard". Skard and another nearby farm were destroyed by a large lava flow that now forms the {{convert|12.5|km2|abbr=on}} ''Nordurhraun''. In total around {{convert|0.3|km3|abbr=on}} of lava and {{convert|5E7|m3|abbr=on}} of tephra were produced.<ref name="GVP" /><ref name="HANVp14" />

;1440
An eruption may have occurred around 1440 at [[Raudölder]]; despite being close to Hekla this is not classed as an eruption of Hekla based on the [[Silicon dioxide|SiO<sub>2</sub>]] content of the lava.<ref name="HANVp18">Thorarinsson, p. 18</ref><ref name="GVP" /><ref name="VW">{{cite web |url=http://volcano.oregonstate.edu/vwdocs/volc_images/europe_west_asia/eruption_history.html |title=Hekla Eruption History |access-date=7 October 2007 |work=Volcano World |archive-date=6 August 2017 |archive-url=https://web.archive.org/web/20170806082922/http://volcano.oregonstate.edu/vwdocs/volc_images/europe_west_asia/eruption_history.html |url-status=dead }}</ref>

;1510
[[Image:Volcanic bomb from Hekla.jpg|thumb|right|17&nbsp;cm long volcanic bomb found in the lava-fields of Hekla]]
Details of the 1510 eruption were not recorded until a century later. It started on 25 July and was particularly violent (VEI 4), firing [[volcanic bombs]] as far as [[Vördufell]], {{convert|40|km|abbr=on}} west. Tephra was deposited over [[Oddi|Rangárvellir]], Holt and [[Landeyjar]], {{convert|0.2|km3|abbr=on}} in total. A man in Landsveit was killed.<ref name="GVP" /><ref name="HANVp14" />

;1597
A VEI-4 eruption began on 3 January and lasted for over 6&nbsp;months, with {{convert|0.15|km3|abbr=on}} of tephra being deposited to the south-southeast, damaging [[Mýrdalur]].<ref name="GVP" /><ref name="HANVp14" />

;1636–1637
A small (VEI-3) eruption began on 8 May 1636 and lasted for over a year. The {{convert|5E7|m3|abbr=on}} of tephra from the eruption damaged pasture to the northeast causing death of livestock.<ref name="GVP" /><ref name="HANVp15">Thorarinsson, p. 15</ref>

;1693
Starting 13 February and lasting for over 7&nbsp;months the eruption was one of Hekla's most destructive (VEI-4). Initially tephra was produced at 60,000&nbsp;m<sup>3</sup>·s<sup>−1</sup>, {{convert|0.18|km3|abbr=on}} during the entire eruption, which also caused [[lahar]]s and [[tsunami]]. The tephra was deposited to the northwest, destroying and damaging farms and woodland in Þjórsárdalur, Land, Hreppar and [[Biskupstungur]]. Fine ash from the eruption reached Norway. There was damage to wildlife with significant numbers of [[trout]], [[salmon]], [[rock ptarmigan|ptarmigan]] and farm animals dying.<ref name="GVP" /><ref name="HANVp15" />

;1725
[[File:Hekla flank.jpg|thumb|right|The flanks of Hekla]]
A very small eruption, possibly only VEI-1, took place on 2 April 1725, producing flows of lava from locations around Hekla which have since been covered by later lava flows. These eruptions are not classed as of Hekla itself based on the SiO<sub>2</sub> content of the lava.<ref name="HANVp18" /><ref name="GVP" />

;1766–1768
The eruption of 1766 was large (VEI-4) and produced the second largest lava flow, {{convert|1.3|km3|abbr=on}} covering {{convert|65|km2|abbr=on}}, and third largest tephra volume, {{convert|0.24|km3|abbr=on}}, of any Icelandic volcano during the inhabited era. The eruption started at around 3:30 am on 5 April 1766 and ceased in May 1768. Initially a 2–4&nbsp;cm layer of tephra was deposited over [[Austur-Húnavatnssýsla]] and Skagafjördur, resulting in the deaths of both fish and livestock. Rangárvellir, Land and Hreppar also suffered damage. During the eruption up to {{convert|0.5|m|abbr=on}} lava bombs were thrown {{convert|15-20|km|abbr=on}} away, and flooding was caused by the sudden melting of snow and ice on Hekla's slopes.<ref name="GVP" /><ref name="HANVp15" />

;1845–1846
[[File:Hecla from Westman Islands rcgl.jpg|thumb|right|Hekla {{circa|1851}}]]
Hekla was dormant for more than sixty years before 1845, when it suddenly burst forth on 2 September at 9 am:
{{Blockquote|After a violent storm on the night of the 2nd of September in that year, the surface of the ground in the [[Orkney Islands]] was found strown with volcanic dust. There was thus conveyed to the inhabitants of Great Britain an intimation that Hecla had been again at work. Accordingly, tidings soon after arrived of a great eruption of the mountain. On the night of 1 September, the dwellers in its neighbourhood were terrified by a fearful underground groaning, which continued till mid-day on the 2nd. Then, with a tremendous crash, there were formed in the sides of the cone two large openings, whence there gushed torrents of lava, which flowed down two gorges on the flanks of the mountain. The whole summit was enveloped in clouds of vapour and volcanic dust. The neighbouring rivers became so hot as to kill the fish, and the sheep fled in terror from the adjoining heaths, some being burnt before they could escape. On the night of 15 September, two new openings were formed — one on the eastern, and the other on the southern slope — from both of which lava was discharged for twenty-two hours. It flowed to a distance of upwards of twenty miles, killing many cattle and destroying a large tract of pasturage. Twelve miles from the crater, the lava-stream was between forty and fifty feet deep and nearly a mile in width. On 12 October a fresh torrent of lava burst forth, and heaped up another similar mass. The mountain continued in a state of activity up to April 1846; then it rested for a while, and began again in the following month of October. Since then, however, it has enjoyed repose. The effects of these eruptions were disastrous. The whole island was strewn with volcanic ash, which, where it did not smother the grass outright, gave it a poisonous taint. The cattle that ate of it were attacked by a [[murrain]], of which great numbers died. The ice and snow, which had gathered about the mountain for a long period of time, were wholly melted by the heat. Masses of [[pumice]] weighing nearly half a ton were thrown to a distance of between four and five miles.<ref>[http://www.gutenberg.org/ebooks/6131 Wonders of Creation: A descriptive account of volcanoes and their phenomena], T. Nelson & Sons (1872)</ref>|Anonymous, 1872}}
The eruption ceased around 5 April 1846. Initially in this VEI-4 eruption tephra was produced at 20,000&nbsp;m<sup>3</sup>·s<sup>−1</sup>. The tephra deposition of a total amount of {{convert|0.17|km3|abbr=on}} was mainly to the east-southeast; immediately to the east of Hekla the layer was {{convert|20|-|40|cm|abbr=on}} deep. Fine ash was carried to the [[Faroes]], [[Shetland]] and Orkney. Lava flows to the west and north-west covered an area of {{convert|25|km2|abbr=on}} with a volume of {{convert|0.63|km3|abbr=on}} of lava. Large quantities of dark ash were deposited over pasture in the same directions leading to many livestock deaths through fluorosis for the next two years.<ref name="GVP" /><ref name="HANVp17">Thorarinsson, p. 17</ref>

;1878
[[File:Iceland - Approaching Hekla.jpg|thumb|right|Hekla {{circa|1893}}]]
A small eruption (VEI-2) occurred between 27 February 1878 and April 1878, around {{convert|10|km|abbr=on}} east of Hekla, and produced {{convert|0.2|km3|abbr=on}} of lava from two parallel fissures covering {{convert|15.5|km2|abbr=on}}.