Hekla
   HOME

TheInfoList



OR:

Hekla (), or Hecla, is a stratovolcano in the south of
Iceland Iceland ( is, Ísland; ) is a Nordic island country in the North Atlantic Ocean and in the Arctic Ocean. Iceland is the most sparsely populated country in Europe. Iceland's capital and largest city is Reykjavík, which (along with its s ...
with a height of . Hekla is one of Iceland's most active
volcano A volcano is a rupture in the Crust (geology), crust of a Planet#Planetary-mass objects, planetary-mass object, such as Earth, that allows hot lava, volcanic ash, and volcanic gas, gases to escape from a magma chamber below the surface. On Ear ...
es; over 20 eruptions have occurred in and around the volcano since 874. During the
Middle Ages In the history of Europe, the Middle Ages or medieval period lasted approximately from the late 5th to the late 15th centuries, similar to the post-classical period of global history. It began with the fall of the Western Roman Empire ...
, the Icelandic Norse called the volcano the "Gateway to Hell". Hekla is part of a volcanic ridge, long. The most active part of this ridge, a
fissure A fissure is a long, narrow crack opening along the surface of Earth. The term is derived from the Latin word , which means 'cleft' or 'crack'. Fissures emerge in Earth's crust, on ice sheets and glaciers, and on volcanoes. Ground fissure ...
about long named , is considered to be within Hekla proper. Hekla looks rather like an overturned boat, with its keel being a series of craters, two of which are generally the most active. The volcano's frequent large eruptions have covered much of Iceland with
tephra Tephra is fragmental material produced by a volcanic eruption regardless of composition, fragment size, or emplacement mechanism. Volcanologists also refer to airborne fragments as pyroclasts. Once clasts have fallen to the ground, they re ...
, and these layers can be used to date eruptions of Iceland's other volcanoes. Approximately 10% of the tephra created in Iceland in the last thousand years has come from Hekla, amounting to 5 km3. Cumulatively, the volcano has produced one of the largest volumes of
lava Lava is molten or partially molten rock (magma) that has been expelled from the interior of a terrestrial planet (such as Earth) or a moon onto its surface. Lava may be erupted at a volcano or through a fracture in the crust, on land or un ...
of any in the world in the last millennium, around 8 km3.


Etymology

In Icelandic ''Hekla'' is the word for a short hooded cloak, which may relate to the frequent cloud cover on the summit. An early
Latin Latin (, or , ) is a classical language belonging to the Italic branch of the Indo-European languages. Latin was originally a dialect spoken in the lower Tiber area (then known as Latium) around present-day Rome, but through the power of the ...
source refers to the mountain as ''Mons Casule''.Thorarinsson, p. 7


Reputation

After the eruption of 1104, stories, probably spread deliberately through Europe by Cistercian monks, told that Hekla was the gateway to Hell.Thorarinsson, Hekla, p. 4 The Cistercian monk Herbert of Clairvaux wrote in his ''De Miraculis'' (without naming Hekla): A poem by the monk Benedeit from circa 1120 about the voyages of
Saint Brendan Brendan of Clonfert (c. AD 484 - c.577), is one of the early Irish monastic saints and one of the Twelve Apostles of Ireland. He is also referred to as Brendan the Navigator, Brendan the Voyager, Brendan the Anchorite, Brendan the Bold. The ...
mentions Hekla as the prison of
Judas Judas Iscariot (; grc-x-biblical, Ἰούδας Ἰσκαριώτης; syc, ܝܗܘܕܐ ܣܟܪܝܘܛܐ; died AD) was a disciple and one of the original Twelve Apostles of Jesus Christ. According to all four canonical gospels, Judas betr ...
. In the ''Flatey Book Annal'' it was recorded that during the 1341 eruption, people saw large and small birds flying in the mountain's fire which were taken to be souls.Thorarinsson, p. 6 In the 16th century Caspar Peucer wrote that the Gates of Hell could be found in "the bottomless abyss of Hekla Fell". The belief that Hekla was the gate to Hell persisted until the 19th century.Thorarinsson, p. 5 There is still a legend that
witch Witchcraft traditionally means the use of magic or supernatural powers to harm others. A practitioner is a witch. In medieval and early modern Europe, where the term originated, accused witches were usually women who were believed to have us ...
es gather on Hekla during
Easter Easter,Traditional names for the feast in English are "Easter Day", as in the '' Book of Common Prayer''; "Easter Sunday", used by James Ussher''The Whole Works of the Most Rev. James Ussher, Volume 4'') and Samuel Pepys''The Diary of Samuel ...
.


Geology

Hekla has a morphological type between that of a fissure vent and stratovolcano (built from mixed lava and tephra eruptions) sited at a rift-
transform Transform may refer to: Arts and entertainment * Transform (scratch), a type of scratch used by turntablists * ''Transform'' (Alva Noto album), 2001 * ''Transform'' (Howard Jones album) or the title song, 2019 * ''Transform'' (Powerman 5000 album ...
junction in the area where the south Iceland seismic zone and eastern volcanic zone meet. The unusual form of Hekla is found on very few volcanoes around the world, notably Callaqui in
Chile Chile, officially the Republic of Chile, is a country in the western part of South America. It is the southernmost country in the world, and the closest to Antarctica, occupying a long and narrow strip of land between the Andes to the east a ...
. Hekla is situated on a long volcanic ridge of which the 5.5 km ''Heklugjá'' fissure is considered Hekla proper. This fissure opens along its entire length during major eruptions and is fed by a magma reservoir estimated to have a top 4 km below the surface with centroid 2.5 km lower. The tephra produced by its eruptions is high in fluorine, which is poisonous to animals. Hekla's basaltic andesite lava generally has a SiO2 content of over 54%, compared to the 45–50% of other nearby transitional alkaline basalt eruptions (see
TAS classification The TAS classification can be used to assign names to many common types of volcanic rocks based upon the relationships between the combined alkali content and the silica content. These chemical parameters are useful, because the relative proportio ...
). It is the only Icelandic volcano to produce
calc-alkaline The calc-alkaline magma series is one of two main subdivisions of the subalkaline magma series, the other subalkaline magma series being the tholeiitic series. A magma series is a series of compositions that describes the evolution of a mafic m ...
lavas.
Phenocryst 300px, feldspathic phenocrysts. This granite, from the Switzerland">Swiss side of the Mont Blanc massif, has large white plagioclase phenocrysts, triclinic minerals that give trapezoid shapes when cut through). 1 euro coins, 1 euro coin (diameter ...
s in Hekla's lava can contain
plagioclase Plagioclase is a series of tectosilicate (framework silicate) minerals within the feldspar group. Rather than referring to a particular mineral with a specific chemical composition, plagioclase is a continuous solid solution series, more pro ...
, pyroxene, titanomagnetite,
olivine The mineral olivine () is a magnesium iron silicate with the chemical formula . It is a type of nesosilicate or orthosilicate. The primary component of the Earth's upper mantle, it is a common mineral in Earth's subsurface, but weathers quickl ...
, and apatite. When not erupting Hekla is often covered with snow and small
glacier A glacier (; ) is a persistent body of dense ice that is constantly moving under its own weight. A glacier forms where the accumulation of snow exceeds its ablation over many years, often centuries. It acquires distinguishing features, such as ...
s; it is also unusually aseismic with activity only starting 30–80 minutes before an eruption. Hekla is located on the mid-ocean ridge, a diverging plate boundary. Hekla is closely studied today for parameters such as
strain Strain may refer to: Science and technology * Strain (biology), variants of plants, viruses or bacteria; or an inbred animal used for experimental purposes * Strain (chemistry), a chemical stress of a molecule * Strain (injury), an injury to a mu ...
, tilt,
deformation Deformation can refer to: * Deformation (engineering), changes in an object's shape or form due to the application of a force or forces. ** Deformation (physics), such changes considered and analyzed as displacements of continuum bodies. * Defor ...
and other movement and seismic activity. Earthquakes in the volcano's vicinity are generally below
magnitude Magnitude may refer to: Mathematics *Euclidean vector, a quantity defined by both its magnitude and its direction *Magnitude (mathematics), the relative size of an object *Norm (mathematics), a term for the size or length of a vector *Order of ...
2 while it is dormant and magnitude 3 when erupting.


Eruption history

The earliest recorded eruption of Hekla took place in 1104. Since then there have been between twenty and thirty considerable eruptions, with the mountain sometimes remaining active for periods of six years with little pause. Eruptions in Hekla are varied and difficult to predict. Some are very short (a week to ten days) whereas others can stretch into months and years (the 1947 eruption started 29 March 1947 and ended April 1948). But there is a general correlation: the longer Hekla goes dormant, the larger and more catastrophic its opening eruption will be. The most recent eruption was on 26 February 2000.


Prehistoric eruptions

One of the largest
Holocene The Holocene ( ) is the current geological epoch. It began approximately 11,650 cal years Before Present (), after the Last Glacial Period, which concluded with the Holocene glacial retreat. The Holocene and the preceding Pleistocene togeth ...
eruptions in Iceland was the
Hekla 3 The Hekla 3 eruption (H-3) circa 1000 BC is considered the most severe eruption of Hekla during the Holocene. It threw about 7.3 km3 of volcanic rock into the atmosphere, placing its Volcanic Explosivity Index (VEI) at 5. This would have ca ...
(or H3) eruption circa 1000 BC, which threw about 7.3 km3 of
volcanic rock Volcanic rock (often shortened to volcanics in scientific contexts) is a rock formed from lava erupted from a volcano. In other words, it differs from other igneous rock by being of volcanic origin. Like all rock types, the concept of volcanic ...
into the atmosphere, placing its Volcanic Explosivity Index (VEI) at 5. This would have cooled temperatures in the northern parts of the globe for a few years afterwards. Traces of this eruption have been identified in Scottish
peat bog A bog or bogland is a wetland that accumulates peat as a deposit of dead plant materials often mosses, typically sphagnum moss. It is one of the four main types of wetlands. Other names for bogs include mire, mosses, quagmire, and muskeg; a ...
s, and in Ireland a study of tree rings dating from this period has shown negligible tree ring growth for a decade.Pg 68 Unless otherwise stated eruption dates are from Global Volcanism Program, other sources disagree. Hekla 3, 4, and 5 produced huge amounts of rhyolitic ash and tephra, covering 80% of Iceland and providing useful date markers in soil profiles in other parts of Europe such as Orkney, Scandinavia, and elsewhere. H3 and H4 produced the largest layers of tephra in Iceland since the last ice age. During the last 7,000 years, one third of the volcanic ash deposited in Scandinavia, Germany, Ireland, and the United Kingdom originated from Hekla.


1104 to 1878

;1104 (H1) Hekla had been dormant for at least 250 years when it erupted explosively in 1104 (probably in the autumn), covering over half of Iceland (55,000 km2) with 1.2 km3 / 2.5 km3 of 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 in Þjórsárdalur valley (15 km away), Hrunamannaafréttur (50 km away) and Lake Hvítárvatn (70 km away) were abandoned because of the damage. The eruption caused Hekla to become famous throughout Europe.Thorarinsson, p. 11 ;1158 A VEI-4 eruption began on 19 January 1158 producing over 0.15 km3 of
lava Lava is molten or partially molten rock (magma) that has been expelled from the interior of a terrestrial planet (such as Earth) or a moon onto its surface. Lava may be erupted at a volcano or through a fracture in the crust, on land or un ...
and 0.2 km3 of tephra. It is likely to be the source of the ''Efrahvolshraun'' lava on Hekla's west. ;1206 The VEI-3 eruption began on 4 December. ;1222 The VEI-2 eruption and the 1206 eruption distributed around 0.24 km3 of tephra mainly to the northeast. ;1300–1301 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 30,000 km2 of land with 0.31 km3 of tephra. Over 0.5 km3 of lava was also expelled. The tephra caused significant damage to the settlements of
Skagafjörður Skagafjörður () is a deep fjord and its valley in northern Iceland. Location Skagafjörður, the fjord, is about 40 km long and 15 km wide, situated between Tröllaskagi to the east and the Skagi Peninsula to the west. There are t ...
and Fljót, leading to over 500 deaths that winter.Thorarinsson, p. 14 The material output from this eruption had SiO2 levels of between 56% and 64%, and apart from a slight abundance of
olivine The mineral olivine () is a magnesium iron silicate with the chemical formula . It is a type of nesosilicate or orthosilicate. The primary component of the Earth's upper mantle, it is a common mineral in Earth's subsurface, but weathers quickl ...
the lava, was typical of Hekla eruptions. ;1341 A small eruption (VEI-3) started on 19 May and deposited around 5×107 m3 of tephra over the areas west and southwest of Hekla, leading to many cattle deaths, probably mainly from fluorosis. ;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 12.5 km2 ''Nordurhraun''. In total around 0.3 km3 of lava and 5×107 m3 of tephra were produced. ;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 SiO2 content of the lava.Thorarinsson, p. 18 ;1510 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 A volcanic bomb or lava bomb is a mass of partially molten rock (tephra) larger than 64 mm (2.5 inches) in diameter, formed when a volcano ejects viscous fragments of lava during an eruption. Because volcanic bombs cool after they l ...
as far as Vördufell, 40 km west. Tephra was deposited over Rangárvellir, Holt and Landeyjar, 0.2 km3 in total. A man in Landsveit was killed. ;1597 A VEI-4 eruption began on 3 January and lasted for over 6 months, with 0.15 km3 of tephra being deposited to the south-southeast, damaging Mýrdalur. ;1636–1637 A small (VEI-3) eruption began on 8 May 1636 and lasted for over a year. The 5×107 m3 of tephra from the eruption damaged pasture to the northeast causing death of livestock.Thorarinsson, p. 15 ;1693 Starting 13 January and lasting for over 7 months the eruption was one of Hekla's most destructive (VEI-4). Initially tephra was produced at 60,000 m3·s−1, 0.18 km3 during the entire eruption, which also caused lahars and
tsunami A tsunami ( ; from ja, 津波, lit=harbour wave, ) is a series of waves in a water body caused by the displacement of a large volume of water, generally in an ocean or a large lake. Earthquakes, volcanic eruptions and other underwater exp ...
. 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 Trout are species of freshwater fish belonging to the genera '' Oncorhynchus'', '' Salmo'' and '' Salvelinus'', all of the subfamily Salmoninae of the family Salmonidae. The word ''trout'' is also used as part of the name of some non-salm ...
,
salmon Salmon () is the common name for several commercially important species of euryhaline ray-finned fish from the family Salmonidae, which are native to tributaries of the North Atlantic (genus ''Salmo'') and North Pacific (genus '' Oncorhy ...
,
ptarmigan ''Lagopus'' is a small genus of birds in the grouse subfamily commonly known as ptarmigans (). The genus contains three living species with numerous described subspecies, all living in tundra or cold upland areas. Taxonomy and etymology The ge ...
and farm animals dying. ;1725 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 SiO2 content of the lava. ;1766–1768 The eruption of 1766 was large (VEI-4) and produced the second largest lava flow, 1.3 km3 covering 65 km2, and third largest tephra volume, 0.24 km3, 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 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 0.5 m lava bombs were thrown 15–20 km away, and flooding was caused by the sudden melting of snow and ice on Hekla's slopes. ;1845–1846 Hekla was dormant for more than sixty years before 1845, when it suddenly burst forth on 2 September at 9 am: The eruption ceased around 5 April 1846. Initially in this VEI-4 eruption tephra was produced at 20,000 m3·s−1. The tephra deposition (0.17 km3) was mainly to the east-southeast; immediately to the east of Hekla the layer was 20–40 cm deep. Fine ash was carried to the Faroes, Shetland and Orkney. Lava flows to the west and northwest covered an area of 25 km2 with 0.63 km3 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.Thorarinsson, p. 17 ;1878 A small eruption (VEI-2) occurred between 27 February 1878 and April 1878, around 10 km east of Hekla, and produced 0.2 km3 of lava from two parallel fissures covering 15.5 km2.


1913 to 1948

;1913 A small eruption (VEI-2) occurred between 25 April 1913 and 18 May 1913, around 10 km east of Hekla, and caused large fissures at Mundafell and Lambafit which produced 3.8 and 6.3 km2 of lava respectively. ;1947–1948 The VEI-4 eruption started on 29 March 1947 and ended on 21 April 1948. It is likely that this was both the second greatest lava eruption of Hekla whilst Iceland was inhabited and the second greatest lava eruption in the world in the period 1900–1970. A total lava volume 0.8 km3 was produced with 0.21 km3 of tephra. The height of Hekla was 1,447 m before the eruption, increasing to a maximum of 1,503 m, before dropping to 1,491 m subsequently. The eruption occurred over a century after the last eruption of Hekla proper, the longest dormant period since 1104. Before the eruption the volcano had been visible from the surrounding area but nothing remarkable was noticed. The eruption occurred at 6:41 am ± 3 min with a loud roar; later eruptions could be heard throughout Iceland. An earthquake at 6:50 am measured 6 on the Mercalli intensity scale and increased the eruption intensity until it covered a 4 km fissure on the ridge. The cloud from the eruption had ascended to a height of 30 km by 7:08 am, the wind then carried it southwards towards
Eyjafjallajökull Eyjafjallajökull (; ), sometimes referred to by the numeronym E15, is one of the smaller ice caps of Iceland, north of Skógar and west of Mýrdalsjökull. The ice cap covers the caldera of a volcano with a summit elevation of . The volcan ...
, turning it black. Pumice first landed on Fljótshlíð at around 7:10 am, and tephra and ash continued falling until it formed a 3–10 cm layer. A lava bomb that landed 32 km from Hekla was 0.5 m across and weighed 20 kg. Between Vatnafjöll and Hekla, a layer of tephra up to a metre thick was deposited, including bombs with a diameter larger than 0.5 m. Bombs with areas of 50 m2 were dropped onto the slopes of Hekla, up to 1 km away. 51 hours after the eruption had started, ash fell on
Helsinki Helsinki ( or ; ; sv, Helsingfors, ) is the capital, primate, and most populous city of Finland. Located on the shore of the Gulf of Finland, it is the seat of the region of Uusimaa in southern Finland, and has a population of . The city ...
, Finland, having covered 2,860 km in this time. The initial tephra production rate in the first 30 minutes of the eruption was 75,000 m3·s−1, dropping to 22,000 m3·s−1 for the next half-hour. The initial phase produced 0.18 km3 of tephra, equating to 4.5×107 m3 of solid rock, covering 3,130 km2 of land and sea. 98 farms were damaged by the eruption, but only 2 were no longer farmed in 1970. A large volunteer effort was mobilized to clear the tephra – around 1000 man-days by the end of July. The eruption produced around 3 ML of water (snowmelt and directly from the fissure) which caused flooding of the Ytri Rangá river. In the first 20 hours of the eruption approximately 3,500 m3·s−1 of lava was produced from the fissure, dividing into various branches and covering 12–15 km2. On the second day, 8 distinct
eruption column An eruption column or eruption plume is a cloud of super-heated Volcanic ash, ash and tephra suspended in volcanic gas, gases emitted during an explosive volcanic eruption. The volcanic materials form a vertical column or Plume (fluid dynamics), ...
s were discernible. A crater formed at 860 m called the Lava Crater (''Hraungígur''), producing a constant flow of lava. Another crater named the Shoulder Crater (''Axlargígur'') produced a column of smoke every 10 seconds together with loud explosions that created visible compression waves in the smoke. By the fourth, fifth, and sixth days, the eruption was greatly diminished, and only the shoulder and summit craters were erupting explosively. The explosive eruption increased in strength from 9–12 April and then from 28 April it reduced again. On 3 May, the volcano stopped throwing out lava in sudden explosions from its craters and changed to continuously ejecting tephra and ash for long periods, until early June when this reduced. On 2 September, the Shoulder Crater had a 960 m circumference at its top and the Summit Crater a 700 m circumference at its highest point, 90 m above the ridge. Sandy tephra and ash fell over Iceland in May and June, sometimes making it dark in the daytime near Hekla. The tephra caused fluorine poisoning of grazing sheep, making them unable to walk. That winter more craters formed, building up cones. Explosive activity had ceased six months after the first eruption. Lava flowed from the Lava Crater continuously during the eruption, starting at a rate of over 100 m3·s−1, dropping to 5–10 m3·s−1 in April and early May at a speed of around 20 cm·s−1 before increasing, eventually reaching 150 m3·s−1 at the end of June and at similar levels until mid-July with a peak flow speed of 2–2.5 m·s−1. From there it gradually decreased to under 10 m3·s−1 in November. Initially the lava comprised 57–58% SiO2 and 11% Fe2O3, from the time of peak flow onwards this changed to 54% SiO2 and 13.5% Fe2O3. The lava river sometimes ran through
lava tubes A lava tube, or pyroduct, is a natural conduit formed by flowing lava from a volcanic vent that moves beneath the hardened surface of a lava flow. If lava in the tube empties, it will leave a cave. Formation A lava tube is a type of lava ca ...
before emerging again. The lava front had a height of up to 15 m. On 15 and 16 June, a branch of lava flow to the south of Melfell traveled over 1 km in 30 hours before slowing and stopping by 21 June, 7.8 km from the Lava Crater. The longest lava stream produced was 8 km long and stopped in Stóraskógsbotnar. A scientist filming one of the lava streams on 2 November was hit by a block of lava and was killed. The lava flow stopped after 13 months on 21 April, having covered 40 km2 and with a maximum depth of 100 m. The lava beds produced were mainly the
ʻAʻā Lava is molten or partially molten rock (magma) that has been expelled from the interior of a terrestrial planet (such as Earth) or a moon onto its surface. Lava may be erupted at a volcano or through a fracture in the crust, on land or und ...
lava type with
Pāhoehoe Lava is molten or partially molten rock (magma) that has been expelled from the interior of a terrestrial planet (such as Earth) or a moon onto its surface. Lava may be erupted at a volcano or through a fracture in the crust, on land or un ...
and ''lava a budella'' (lava tubes) areas. In April and May 1948 CO2 emitted from cracks in the ground pooled in hollows near to Hekla, killing 15 sheep and some wild animals and birds. In total 24,000 tonnes of CO2 was emitted. Ditches were dug by farmers to drain these hollows, and the CO2 emission had stopped by the end of the year.Thorarinsson, pp. 19–38


1970 to 1991

;1970 The 1970 eruption of Hekla started at 9:23 pm on 5 May 1970 and lasted until 5 July. It had a VEI of 3 and produced 0.2 km³ of lava covering an area of 18.5 km² and 6.6×10 7 m³ of tephra, deposited over an area of 40,000 km², mainly to the northwest of the volcano. The main Hekla fissure only erupted at its far southwest end, most of the eruption was from other fissures nearby. The eruption stopped in the south-southwest on 10 May and in Hlídargígar on 20 May, but a new fissure opened on the same day and lava flowed from this until 5 July. The lava was andesite containing olivine, similar to the lava produced later in the eruption of 1947.Thorarinsson, pp. 39–58 Before the eruption, a greater than normal amount of snow melting had occurred, indicating the volcano was heating up. Earth tremors began at 8:48 pm on the evening of the eruption; the largest had a magnitude of 4. The eruption started weakly at 9:23 pm IMT ± 2 min before increasing in power. The first pumice fell on Búrfell power station, 15 km away, at 9:35 pm causing people to evacuate. The eruption seems to have started in two locations at the same time – to the Shoulder crater's south-southwest and below the Lava Crater. At 10:30 pm a crater at 780 m was producing a lava column which reached an altitude of around 1000 m. During the night a 700 m high lava fountain was thrown up from the main crater. A 500 m long fissure starting below the Lava Crater opened and lava fountains and other lava flows emanated from it. One hour into the eruption, a new 400 m fissure opened to the northeast, producing two main lava fountains, and shortly after another adjoining fissure opened producing lava fountains to a height of 500 m. At around midnight, another fissure opened northwest of the Lava Crater, later hurling an over 300 m long lava fountain, 200–300 m into the air. By midnight lava had already covered over 1 km² and this extended to 7.5 km² by next morning implying a flow rate of around 1500 m³/s. For the first two hours, tephra was produced at the rate of 10,000 m³/s. The cloud from the eruption, which had reached by 10:10 pm, caused a lightning storm. The tephra was transported northwards by the wind, causing the sky to turn black in places – 190 km away at Blönduós tephra fell from midnight until 2 am, and ash fell on a trawler 330 km away at 2 am. Icelanders sampled the tephra fall in their locality by putting a plate outside to capture everything that fell onto it. This, and other measurements, showed the area covered was long and narrow with the 1 mm contour (an equivalent of 8 tonnes per hectare) extending to the north coast. By 5:30 on 6 May, the lava flow measured 4 km long. Many lava bombs were found near the main crater, one had an area of 6 m² and a likely weight of 12 tons.
Xenolith A xenolith ("foreign rock") is a rock fragment ( country rock) that becomes enveloped in a larger rock during the latter's development and solidification. In geology, the term ''xenolith'' is almost exclusively used to describe inclusions in ig ...
s formed around 2% of the material produced by the craters. These were of rock types including basalt, andesite,
ignimbrite Ignimbrite is a type of volcanic rock, consisting of hardened tuff. Ignimbrites form from the deposits of pyroclastic flows, which are a hot suspension of particles and gases flowing rapidly from a volcano, driven by being denser than the surro ...
and
sedimentary rock Sedimentary rocks are types of rock that are formed by the accumulation or deposition of mineral or organic particles at Earth's surface, followed by cementation. Sedimentation is the collective name for processes that cause these particles ...
. The eruption became stronger at Skjólkvíar on 12 May, with columns of steam attaining a height of 2500 m. The eruption intensity then gradually reduced until it stopped on 20 May. The lava field then had an area of 5.8 km². Later that day a 900 m long fissure opened 1 km north of the main Hlídargígar crater. That night it contained 17 lava fountains, each 20–50 m in height. By the evening of the next day, 10–12 craters had formed, each throwing pieces of lava 50–100 m in the air. This row of craters was named Öldugígar. Gradually the number of active craters decreased, the most active of these built a cone 100 m higher than the level of the ridge. Lava flowed from its base until mid-June when the lava cut through the north crater wall. The larger cones produced more tephra, occasionally with lightning within the tephra cloud. By 5 July, the eruption had stopped. During eruptions of Hekla, fluorine is produced and sticks to the surfaces of the grains of tephra. Fine grains can have a fluorine content of 350 ppm, and fluorine poisoning can start in sheep at a diet with fluorine content of 25 ppm. At 250 ppm, death can occur within a few days. In 1783, 79% of the Icelandic sheep stock were killed, probably as a result of fluorosis caused by the eruption of Lakagígar. Some of the ash produced in this eruption had a fluorine content of 0.2%, and two days after the eruption contaminated grass had a dry weight content of up to 0.4% fluorine. 450 farms and 95,000 sheep were affected by the eruption. Some sheep were kept inside and fed on hay or moved, but other farmers were forced to graze their flocks outside. ;1980 and 1981 This VEI-3 eruption started at 13:28 on 17 August 1980 and lasted until 20 August 1980. It was a mixed eruption producing a lava volume of 0.12 km³ and a tephra volume of 5.8×107 m³. The fissure opened along a 7 km length. Shortly before the eruption started a steam column was produced; eventually the
eruption column An eruption column or eruption plume is a cloud of super-heated Volcanic ash, ash and tephra suspended in volcanic gas, gases emitted during an explosive volcanic eruption. The volcanic materials form a vertical column or Plume (fluid dynamics), ...
reached a height of 15 km. The main tephra deposits were to the north-northeast and lasted for around 2 hours. Deposits were 20 cm thick 10 km from the summit, decreasing to less than 1 mm at the coast 230 km away. Lava was initially produced from close to the summit, spreading to other parts of the fissure and covering an area of 22 km² in around 24 hours. The last
scoria Scoria is a pyroclastic, highly vesicular, dark-colored volcanic rock that was ejected from a volcano as a molten blob and cooled in the air to form discrete grains or clasts.Neuendorf, K.K.E., J.P. Mehl, Jr., and J.A. Jackson, eds. (2005) '' ...
were seen on the morning of 20 August. This was an unusual eruption both in the short time since the previous eruption – the shortest since 1104, and the length – previous eruptions had lasted from 2 months to 2 years rather than just 3 days. The 1981 eruption, which is regarded as being a continuation of the previous year's eruption, began at 3 am on 9 April 1981, had a VEI of 2 and produced 3×107 m³ of lava, lasting until 16 April 1981. The eruption threw ash to a height of 6.6 km, and a new crater formed at the summit from which 3 lava flows originated. These extended to a maximum of 4.5 km from the volcano, covering 5–6 km². ;1991 A VEI-3 eruption occurred from 17 January 1991 to 11 March 1991, producing 0.15 km³ of lava and 2×107 m³ of tephra. The eruption, which was preceded by sulphurous smells and earthquakes, started as a Plinian eruption, producing an ash cloud reaching an altitude of 11.5 km within 10 minutes which had travelled over 200 km north-northeast to the coast within 3 hours. The eruption then began producing andesitic lava, the flows eventually covering an area of 23 km² to an average depth of 6–7 m. Initially, part of the Heklugja fissure and other fissures erupted with lava fountains reaching 300 m in height. By the second day, the activity stopped in all but one fissure where the main crater formed. During these 2 days, 800 m³/s of lava were produced, slowing to between 1 m³/s and 14 m³/s for most of the eruption. This low
viscosity The viscosity of a fluid is a measure of its resistance to deformation at a given rate. For liquids, it corresponds to the informal concept of "thickness": for example, syrup has a higher viscosity than water. Viscosity quantifies the inte ...
lava had a SiO2 content of approximately 54%.


2000

The most recent eruption was relatively short; it started at 18:18 on 26 February 2000 and lasted until 8 March. It was a VEI-3 eruption producing a lava volume of 0.189 km3 DRE / 0.29 km3 and 107 m3 of tephra. The eruption went through four phases: #initial explosive stage #fire fountains #bursts of Strombolian eruption #effusion of lava Eruption activity was at a maximum in the first hour, and by the first night the fissure on Hekla had opened to a length of 6–7 km. The steam column rose to a height of almost 15 km, and ash was transported to
Grímsey Grímsey () is a small Icelandic island, off the north coast of the main island of Iceland, straddling the Arctic Circle. In January 2018 Grímsey had 61 inhabitants. Before 2009, Grimsey constituted the ''hreppur'' (municipality) of Grí ...
on the North coast of Iceland. During this eruption, a
NASA The National Aeronautics and Space Administration (NASA ) is an independent agencies of the United States government, independent agency of the US federal government responsible for the civil List of government space agencies, space program ...
DC-8 The Douglas DC-8 (sometimes McDonnell Douglas DC-8) is a long-range narrow-body airliner built by the American Douglas Aircraft Company. After losing the May 1954 US Air Force tanker competition to the Boeing KC-135, Douglas announced in Ju ...
aeroplane accidentally flew through the plume with all instruments switched on, resulting in unprecedented measurement of a young volcanic plume. Up until this eruption, it had been assumed that Hekla was incapable of producing the most dangerous of volcanic phenomena, the pyroclastic flow. In January 2003, however, a team from the Norvol Institute in
Reykjavík Reykjavík ( ; ) is the capital and largest city of Iceland. It is located in southwestern Iceland, on the southern shore of Faxaflói bay. Its latitude is 64°08' N, making it the world's northernmost capital of a sovereign state. With a po ...
, under the leadership of Dr. Ármann Höskuldsson, reported that they found traces of a pyroclastic flow, roughly 5 km long, stretching down the side of the mountain. This will call for a reappraisal of volcanic eruptions of the basic rock type, which up to now were generally thought not to produce large pyroclastic flows. It will also require that the public and curious spectators who always rush to the scene at the start of a new outbreak, be kept much further away from the volcanic activity than was thought necessary during previous outbreaks.


Flora and fauna

The Hekla area was once forested. Forest and some grasses are much more resilient to ash and pumice fall than low vegetation, but the combined effect of human habitation and the volcanic activity has left an unstable surface very susceptible to erosion. Hekluskógar, a 90,000 ha reforesting project is attempting to restore the
birch A birch is a thin-leaved deciduous hardwood tree of the genus ''Betula'' (), in the family Betulaceae, which also includes alders, hazels, and hornbeams. It is closely related to the beech- oak family Fagaceae. The genus ''Betula'' contains ...
and
willow Willows, also called sallows and osiers, from the genus ''Salix'', comprise around 400 speciesMabberley, D.J. 1997. The Plant Book, Cambridge University Press #2: Cambridge. of typically deciduous trees and shrubs, found primarily on moist so ...
woodland to the slopes of Hekla, starting with soil fertilisation and grass sowing. This would stabilize the large areas of
volcanic ash Volcanic ash consists of fragments of rock, mineral crystals, and volcanic glass, created during volcanic eruptions and measuring less than 2 mm (0.079 inches) in diameter. The term volcanic ash is also often loosely used to refer ...
, help to reduce wind erosion of the
frost heave Frost heaving (or a frost heave) is an upwards swelling of soil during freezing conditions caused by an increasing presence of ice as it grows towards the surface, upwards from the depth in the soil where freezing temperatures have penetrated in ...
d surface, slow drainage rates and hence
water erosion Erosion is the action of surface processes (such as water flow or wind) that removes soil, rock, or dissolved material from one location on the Earth's crust, and then transports it to another location where it is deposited. Erosion is dist ...
, and ultimately increase
biodiversity Biodiversity or biological diversity is the variety and variability of life on Earth. Biodiversity is a measure of variation at the genetic (''genetic variability''), species (''species diversity''), and ecosystem (''ecosystem diversity'') l ...
. It is the largest reforestation of its type in Europe. After an eruption, almost all of the 'safe sites' on new lava flows are colonised by mosses within 20 years expanding to a homogeneous layer up to 20 cm thick within 50 years.


Sport and recreation

Hekla is a popular destination for hiking. Following the most recent eruption the path goes most of the way to the summit; the walk takes 3 to 4 hours. In spring,
skiing Skiing is the use of skis to glide on snow. Variations of purpose include basic transport, a recreational activity, or a competitive winter sport. Many types of competitive skiing events are recognized by the International Olympic Committee ( ...
is possible on short routes around the rim of the crater. In summer, there are easy ( F) mountaineering routes also around the crater rim, and it is possible to snowcat to the top in winter. The volcano can be reached using the buses to
Landmannalaugar Landmannalaugar () is a location in Iceland's Fjallabak Nature Reserve in the Highlands. It is at the edge of the Laugahraun lava field, formed in an eruption in approximately 1477. It is known for its natural geothermal hot springs and ...
30 km further east, and it is possible to stay or camp at farms in the area. A visitor centre, The Hekla Center at Leirubakki Farm, opened in 2007.


In popular culture

Hekla has featured in artistic works since the time of its medieval infamy.


Films

In the Spanish apocalyptic
science fiction Science fiction (sometimes shortened to Sci-Fi or SF) is a genre of speculative fiction which typically deals with imaginative and futuristic concepts such as advanced science and technology, space exploration, time travel, parallel uni ...
film, '' Los Últimos Días'' (2013), some news reporters speculate that three recent eruptions of Mount Hekla could have caused the spreading form of agoraphobia that kills affected people who go outside. The climax of
Robert Eggers Robert Houston Eggers (born July 7, 1983) is an American filmmaker, director, and production designer. He is best known for writing and directing the historical horror films '' The Witch'' (2015) and '' The Lighthouse'' (2019), as well as directi ...
's 2022 film ''
The Northman ''The Northman'' is a 2022 American epic historical action thriller film directed by Robert Eggers, who co-wrote the screenplay with Sjón. Based on the legend of Amleth, the film stars Alexander Skarsgård (who also produced), Nicole Kidman ...
'' takes place on the slopes of Hekla.


Food

In the Boston, Massachusetts area, Hekla pastries can be found – large, upside-down cinnamon rolls with white sugar icing spooned over the top to look like the snow-topped volcano.


Literature

The British poet
William Blake William Blake (28 November 1757 – 12 August 1827) was an English poet, painter, and printmaker. Largely unrecognised during his life, Blake is now considered a seminal figure in the history of the poetry and visual art of the Romantic Age. ...
showed Winter being banished to Hekla in ''To Winter'', one of the works from his ''Poetical Sketches''. In '' To Lie With Lions'', by
Dorothy Dunnett Dorothy, Lady Dunnett (née Halliday, 25 August 1923 – 9 November 2001) was a Scottish novelist best known for her historical fiction. Dunnett is most famous for her six novel series set during the 16th century, which concern the fictiti ...
, a party of merchants visiting Iceland in the year 1471 witnesses the spectacular (fictional) eruption of both Hekla and Katla. Mt. Hekla is referenced in the third chapter of
Herman Melville Herman Melville ( born Melvill; August 1, 1819 – September 28, 1891) was an American novelist, short story writer, and poet of the American Renaissance period. Among his best-known works are ''Moby-Dick'' (1851); ''Typee'' (1846), a rom ...
's novel ''
Moby Dick ''Moby-Dick; or, The Whale'' is an 1851 novel by American writer Herman Melville. The book is the sailor Ishmael's narrative of the obsessive quest of Ahab, captain of the whaling ship ''Pequod'', for revenge against Moby Dick, the giant whi ...
'', in EE Ryan's '' The Odd Saga of the American and a Curious Icelandic Flock'', and in the final chapters of
Joan Aiken Joan Delano Aiken (4 September 1924 – 4 January 2004) was an English writer specialising in supernatural fiction and children's alternative history novels. In 1999 she was awarded an MBE for her services to children's literature. For ''The ...
's novel '' Is''. The
Hekla 3 The Hekla 3 eruption (H-3) circa 1000 BC is considered the most severe eruption of Hekla during the Holocene. It threw about 7.3 km3 of volcanic rock into the atmosphere, placing its Volcanic Explosivity Index (VEI) at 5. This would have ca ...
eruption and the ensuing
volcanic winter A volcanic winter is a reduction in global temperatures caused by volcanic ash and droplets of sulfuric acid and water obscuring the Sun and raising Earth's albedo (increasing the reflection of solar radiation) after a large, particularly explosiv ...
play a large role in Stephen Baxter's alternate-history novel ''Bronze Winter''.


Music

The piece ''Hekla'', Op 52 (1964) by Icelandic composer Jón Leifs, has been called the "loudest classical music of all time". The requirements for a performance of ''Hekla'' include four sets of rocks hit with hammers, steel plates, anvils, sirens, cannons, metal chains, choir, a large orchestra, and organ.


Transportation

A small Danish cruiser launched in 1890 was named ''
Hekla Hekla (), or Hecla, is a stratovolcano in the south of Iceland with a height of . Hekla is one of Iceland's most active volcanoes; over 20 eruptions have occurred in and around the volcano since 874. During the Middle Ages, the Icelandic Nor ...
''; it was scrapped in 1955. A Danish steamer called
Hekla Hekla (), or Hecla, is a stratovolcano in the south of Iceland with a height of . Hekla is one of Iceland's most active volcanoes; over 20 eruptions have occurred in and around the volcano since 874. During the Middle Ages, the Icelandic Nor ...
also saw combat in the
First Schleswig War The First Schleswig War (german: Schleswig-Holsteinischer Krieg) was a military conflict in southern Denmark and northern Germany rooted in the Schleswig-Holstein Question, contesting the issue of who should control the Duchies of Schleswi ...
. Icelandair named one of their aircraft after Hekla. There have been several ships of the
Royal Navy The Royal Navy (RN) is the United Kingdom's naval warfare force. Although warships were used by English and Scottish kings from the early medieval period, the first major maritime engagements were fought in the Hundred Years' War against ...
named HMS ''Hecla''


Organizations

In October 2011 a German left-wing militant group called the '' Hekla-Empfangskomitee'' (Hekla Reception Committee) set at least 17 incendiary devices on railways in the Berlin area, with 2 of them going off. The DBU Copenhagen football club '' Boldklubben Hekla'' play at Hekla Park.


See also

*
Geography of Iceland Iceland ( ) is an island country at the confluence of the North Atlantic and Arctic oceans, east of Greenland and immediately south of the Arctic Circle, atop the constructive boundary of the northern Mid-Atlantic Ridge about from Scotland and ...
*
Iceland plume The Iceland hotspot is a hotspot which is partly responsible for the high volcanic activity which has formed the Iceland Plateau and the island of Iceland. Iceland is one of the most active volcanic regions in the world, with eruptions occur ...
* Iceland hotspot * List of volcanoes in Iceland *
Volcanism of Iceland :''The volcano system in Iceland that started activity on August 17, 2014, and ended on February 27, 2015, is Bárðarbunga.'' :''The volcano in Iceland that erupted in May 2011 is Grímsvötn.'' Iceland experiences frequent volcanic activity, ...


References


Bibliography

*


External links


Hekla
in the Catalogue of Icelandic Volcanoes
Hekla – picture gallery from islandsmyndir.is


*
Latitude, longitude and depth of earthquakes near Hekla from 2000 to March 2013
{{Authority control 19th-century volcanic events 20th-century volcanic events Active volcanoes Central volcanoes of Iceland East Volcanic Zone of Iceland Mountains of Iceland One-thousanders of Iceland Stratovolcanoes of Iceland VEI-5 volcanoes Volcanic systems of Iceland