Hekla

This article covers the volcano in Iceland. For further meanings see Hekla (disambiguation) .

Hekla
Hekla
height	1491  m
location	Iceland
Coordinates	63 ° 59 ′ 32 ″  N , 19 ° 40 ′ 0 ″  W Coordinates: 63 ° 59 ′ 32 ″  N , 19 ° 40 ′ 0 ″  W
Type	Stratovolcano
Age of the rock	at least 600,000 years
Last eruption	February 2000
First ascent	June 20, 1750 by Eggert Ólafsson and Bjarni Pálsson (probably)
Heklagipfel 2005
Hekla from the south

Hekla 2006

Hekla on a map by Abraham Ortelius from 1585

Hekla in winter 2007

Hekla 2010 with ashes from the eruption of Eyjafjallajökull

The Hekla ([ ˈhɛʰkla ], Icelandic for hood ) is a 1491  m high volcano in the south of Iceland , in the municipality of Rangárþing ytra . The Hekla is the central volcano of a 40 km long volcanic fissure and is at least 6600 years old. The mountain is one of the three most active volcanoes in Iceland. The considerable eruptions of the volcano have repeatedly covered large parts of Iceland with volcanic ash and pumice ( tephra ). About ten percent of the tephra that has been emitted in Iceland in the past 1000 years comes from the Hekla, that is about five cubic kilometers. In addition, about eight cubic kilometers of lava were released during this time.

location

The volcano is located northeast of the municipality of Hella and about 25 km west of Landmannalaugar in the highlands of Iceland . The distance to Reykjavík is 107 km.

Legends about Hekla and reception

In the Middle Ages , the gate to hell was believed to be at the summit of Hekla . This is due, among other things, to the fact that an eruption of the volcano in 1104 prevented the settlement of an entire valley, the upper Þjórsádalur . Remnants of the Stöng farm attest to this settlement. The Flateyjarbók manuscript describes the eruption of 1341, when observers saw large and small birds flying out of the crater, which were mistaken for souls. On the map of Iceland by cartographer Abraham Ortelius from 1585, the volcano Hekla is shown during an eruption. The Latin text alludes to the souls of the damned who should be in it.

Around 1590, Oddur Einarsson , Bishop of Skálholt , wrote in his book Íslandslýsing that only a few would have tried to climb Hekla to see whether there was really fire in it. Only one person was able to climb successfully: " Engum hafði þó tekist ætlunarverkið en þó hafði Oddur spurnir af einum manni þar í grenndinni er upp hafði komist, og séð hvernig umhorfs var, en samt hafi er brug hanni ð samtvo ð er brugannið samt heima, að hann hafi verið sem vitskertur og ekki lifað lengi eftir það ”(German:“ (...) and when he saw what it looked like there, he was so shocked that he was out of his mind after his return home and afterwards did not live long. ")

When, in 1750, the reconnaissance men Eggert Ólafsson and Bjarni Pálsson wanted to climb the mountain, they were urgently advised against such an undertaking that literally “challenged all the devils of hell” and one companion fell into severe stomach cramps out of fear .

The Icelandic composer Jón Leifs wrote Hekla in 1961 for mixed choir, organ and orchestra. In addition to a generally large cast, there are also 19 percussionists in two groups who play anvils, large and small stones, sirens, bells, iron chains, large wooden boxes, rifles and cannons.

In Swedish there is the curse Dra åt Häcklefjäll! (Eng. "Go to Hekla!"), which is used synonymously with the curse "Go to hell!"

The geologist Ari Trausti Guðmundsson describes the Hekla as perhaps the most famous mountain in the country.

geology

The Hekla is located at a triple point where the southern Icelandic earthquake zone meets the eastern volcanic zone. The 40 km long volcanic system includes numerous craters (including the Vatnafjöll crater ), with Hekla being the central volcano. It lies on a column aligned with the WSW-ONO and has built up through repeated breakouts.

The Hekla is a hybrid of crevasse and stratovolcano . A 5 km long eruption crevice , the Heklugjá , stretches across the main summit , on which a main crater has built up in the eruptions of recent years. In the event of an eruption , the entire column usually opens lengthways.

Based on geodetic measurements, the magma chamber of the Hekla could be located at a depth of 11 km. Their size is estimated at around 25 km ³ . Due to segregation in the magma chamber during the volcanic dormant phases, the composition of the lava gradually changes from a rhyolite (63% SiO ₂ ) to an andesitic (54% SiO ₂ ) composition in the course of an eruption . The tephra emitted by Hekla contains a high proportion of fluorides , which are toxic to animals and therefore can make pastures unusable for livestock use. The phenocrystals in the lava rock of the Hekla consist of minerals such as feldspar , pyroxene , titano magnetite , olivine and apatite . The tephras of the Hekla have a characteristic composition and can therefore be used very well for dating by means of tephrochronology .

When it is resting, the Hekla is often covered with snow and small glaciers. Earthquakes in their area are rare. The earthquake activity usually only begins around 30–80 minutes before an eruption. Earthquakes on the Hekla are usually below magnitude 2 when it is in a dormant phase and around magnitude 3 when it is erupted.

Hekla earthquake activity , soil deformation and gas emissions are monitored by geologists from the Icelandic Meteorological Service (Veðurstofa Ísland).

Eruption dynamics

The Hekla eruptions are generally difficult to predict in the long term. Some are short-lived, such as that of 2000, while others can last for months and years, such as that of 1947 (March 29, 1947 to April 1948). As with other volcanoes, the following applies here: the longer the volcano is idle, the more powerful or even more catastrophic the subsequent eruption.

In recent years, the outbreaks mostly followed a certain pattern. They begin with a short explosive phase (Plinian), during which there is an outbreak of Dazite and Andesite tephren and the formation of pyroclastic currents (glowing clouds). This explosive phase usually lasts a few hours and is concentrated on the summit crater. The eruption then turns into an effusive fissure eruption along the Heklugjá , releasing andesitic lavas. The effusive phase lasts for a few hours to weeks. The erupted lava has a rhyolitic (63% SiO ₂ ) to andesitic (54% SiO ₂ ) composition, whereby the composition of the lava during an eruption (proven since 1510) always changes according to the same pattern: the longer the pre-eruptive rest phase was , the higher the SiO ₂ proportion of the magma ejected at the beginning of an eruption. As the eruption continues, the SiO ₂ content drops to 54%. The effect is due to a segregation of the magma in the magma chamber (gravitational differentiation: rise of phases with lower density and decrease of phases with higher density) during the volcanic rest phases.

High-resolution geodetic measurements (strain meters) were able to prove that a subsidence in the soil due to a reduction in volume in the magma chamber can only be observed during the initial explosive eruption phases. In contrast, no soil deformation occurs during the main phase of the eruption. It follows that during an eruption the magma chamber is refilled at the same rate as magma erupts on the earth's surface. The effusion of magma is therefore controlled by the density buoyancy of the magma and not by the reduction in pressure in the magma chamber. When the differentiated, light material (with> 54% SiO ₂ ) has erupted from the upper part of the magma chamber, the eruption ends. A longer pre-eruptive rest phase therefore leads to a larger eruption, since more material could differentiate and accumulate in the upper part of the magma chamber. The consequence of an already filled magma chamber at the end of an eruption is that it is not the magma feed from the outside that controls the renewed pressure build-up of the system during the volcanic periods of rest, but that instead internal processes in the magma chamber (gas rise) cause the pressure to rise again. The model for self-regulating eruption cycles could thus be derived from the observations at the Hekla.

Eruption history of the Hekla

Around 38 Hekla eruptions were found before Iceland was settled.

Shortly after the ice sheet melted during the last ice age, very voluminous but rather effusive eruptions seem to have taken place, each of which produced up to 15 km³ of lava . However, explosive eruptions with a high ash production rate did not occur until later.

The H3 eruption of the Hekla

This eruption is a very significant one in prehistoric times. It happened around 1159 BC. And is considered to be the most severe eruption of the Hekla during the Holocene .

7.3 km³ of tephra were hurled into the atmosphere, so that this eruption is at level 5 on today's measuring scale for volcanic eruptions VEI . The whole of Iceland was covered by a layer of tephra. Another consequence was the cooling of the Northern Hemisphere for years, which can be proven on Orkney .

There is disagreement about the exact date.

Andy Baker recorded the eruption on 1135 ± 130 BC. Dated. In doing so, he relies on studies of the vegetation in Ireland and the Greenland ice. Particularly narrow annual rings have been discovered in trees and tree remains. However, there is also another dating direction (Dagmore et al.), Which dates the eruption 929 ± 34 BC. Chr. Assumes.

Some Egyptologists and Orkney scientists date the eruption to 1159 BC. Chr., Because z. B. Harvest failures and famines under the rule of Ramses III. could be explained. A third group of scientists has suggested that it was dated around 1050 BC. BC (3000 BP) agreed.

Overview of the known eruptions of the Hekla since the High Middle Ages

After the first documented eruption in 1104, a total of between 20 and 30 other documented eruptions have followed (the number depends on the source. Smithsonian, for example, counts as 2 eruptions in 1980 and 1981.)

Outbreak year	Duration	Break between outbreaks (in years)	Type of eruption	Centers d. eruption	Lava in km³	Tephra in km³	Main direction of the tephra spread	damage
1104	?	200-300	Regional crevasse eruption, explosive			2.5	N	very large
1158	?	53	Regional crevasse eruption, explosive		> 0.15		SSO	low
1206	?	46	Regional crevasse eruption, explosive			0.03?	ONO	low
1222	?	15th	Regional crevasse eruption, explosive			0.01?	O	low
1300	12 months	78	Regional crevasse eruption, explosive		> 0.5	0.5	N	big
1341	?	40	Regional crevasse eruption, explosive			0.06?	WNW	big
1389	?	47	Fissure breakout, explosive	Heklugjá, western flank (Rauðöldur)	> 0.2	0.08?	SSO?	quite large
1440	?		Regional crevasse eruption, explosive	Southeast of the central volcano				some
1510	?	120	Regional crevasse eruption, explosive and effusive			0.32	SW	probably big
1554	?	44	Regional crevasse eruption, explosive and effusive	Southwest of the Heklla, Rauðabjallar				low
1597	> 6 months	45	Regional crevasse eruption, explosive and effusive			0.24?	SO	low
1636	12 months	41	Regional crevasse eruption, explosive and effusive			0.08?	NO	low
1693	7-10 months	57	Regional crevasse eruption, explosive and effusive			0.3	NNW	big
1725	?	34	Regional crevasse eruption, explosive and effusive					low
1766	24 months	41	Regional crevasse eruption, explosive and effusive	Bjallargígar	by 1.3	0.4	N	quite large
1845	7 months	79	Regional crevasse eruption, explosive and effusive, lahars	Heklugjá, SW and NE flanks	0.63	0.28	N	quite large
1878	?	33	Regional crevasse eruption, explosive and effusive	Krakagígar, east d. Central volcanoes				low
1913	24 days	35	Regional crevasse eruption, explosive and effusive	East and northeast of the central volcano, Mundafit, Lambafit				low
1947	13 months	34	Regional crevasse eruption, explosive and effusive	Hraungigur, Axlargigur, Toppgigur	0.8	0.21	S.	low
1970	2 months	22nd	Radial crevice eruption, explosive and effusive	Sudurgígar, Hlíðargígar, Öldugígar	0.2	0.07	NNW	some
1980-1981	1–2 weeks	10	Flank eruption, regional and radial crevice eruption, explosive and effusive, pyroclastic. Currents	Heklugjá, SW and NE flanks	0.15	0.06	N	some
1991	52 days	10	Flank eruption, regional and radial crevice eruption, explosive and effusive	Heklugjá, flank eruptions in the SW, SW and NE	0.15	0.02	NO	low
2000	11 days	9	Regional crevasse eruption, explosive and effusive, pyroclic. Currents	Southwest flank	0.189	0.01	N	low

Eruptions from 1104 to the 16th century

1104 (H1)

The volcano had been in a dormant phase for about 250 years when it came to life in 1104 with a Plinian eruption . It covered more than half of the country (55,000 km²) with 1.2–2.5 km³ of Rhyodacitic tephra.

Like the prehistoric eruption Hekla 3 (H3), the eruption reached level 5 on the volcanic explosion index (VEI). Many farms were destroyed or abandoned as a result, such as the farm of Stöng in upper Þjórsárdalur, which was previously densely populated and has remained deserted to this day. Even the districts of Hrunamannaafréttur , 50 km away, and Lake Hvítárvatn , 70 km away, felt the consequences.

Presumably this eruption gave rise to the particularly bad reputation of this volcano.

1158, 1206, 1222

The January 19, 1158 eruption reached a magnitude of 4 on the VEI scale and produced over 0.15 km³ of lava and 0.2 km³ of tephra. The Efrahvolshraun lava field on the west of the mountain was probably created. The eruptions of 1206 and 1222, the first of which began on December 4th, were not significant (VEI 3 and 2). They produced about 0.24 km³ of tephra.

1300-1301

This is a very significant eruption. It started on July 11th and lasted for a year. 30,000 km², almost a third of the country's surface, was covered with tephra (0.31 km³) and 0.5 km³ of lava was emitted. The pastures in the south were badly damaged, especially in the Fljótshlíð and Skagafjörður districts , resulting in at least 500 deaths the following winter. The discharged material had an SO ₂ content of between 56% and 64% and was typical of the Hekla , apart from a slightly larger olivine content .

1341, 1389 and 1440

A small eruption (VEI level 3) began on May 19, 1341 and placed Tephra on the districts in the west and south-west of the Hekla. Much livestock died, presumably from fluorine poisoning .

Hekla broke out again late in 1389 (VEI 3). The explosive eruption began with Tephrafall in the east of the volcano. The eruption later shifted to a crevice in the then existing forest at Skarð farm , where the farm was destroyed by a lava flow. This lava (12.5 km²) is called Norðurhraun .

Another eruption probably took place near Rauðöldur in 1440 . But it's not entirely clear whether it counts as a Hekla eruption because of the SiO ₂ content of the lava.

Eruptions in the 16th century

Hekla volcanic bomb

Hekla erupted twice in the 16th century, in 1510 and 1597.

Details regarding the 1510 eruption were not recorded until 100 years later, so they are not very reliable. So it started on July 25th and was very explosive. Volcanic bombs flew up to table mountain Vörðufell , 40 km away. Ash fell on Rangárvellir , Holt and Landeyjar , a total of 0.2 km³.

The eruption of 1597 was no weaker (also VEI 4), started on January 3rd and lasted for half a year. 0.13 km³ of tephra fell in the direction of the SSE, especially on the Mýrdalur .

Eruptions in the 17th century

Hekla from Þjórsárdalur from

Hekla also broke out twice in the 17th century: 1636–1637 and 1693. Although the eruption of 1636 was relatively minor (VEI 3), it lasted for over a year. The tephra damaged the pastures in the northeast, so that cattle died. In contrast, the eruption of 1693 is one of the most devastating eruptions of the Hekla ever (VEI 4). It started on January 13th and lasted for over 7 months. A lot of tephra was produced, in total (0.18 km³). Also lahars rushed down the mountain slopes. The affected districts of Þjórsárdalur , Land , Hreppur and Biskupstungur suffered badly. Farms had to be abandoned. Lots of tame and wild animals, i.e. H. also salmon and trout, grouse , etc. died as a result of fluorosis.

Eruptions in the 18th century: 1725 and 1766–1768

On April 2, 1725, a very small effusive eruption occurred, probably VEI1 in the vicinity of the Hekla. The resulting lava flows were later overlaid by others and, because of their SiO ₂ content, were not actually assigned to the Hekla.

A much larger eruption occurred in 1766 (VEI 4). It originated the second largest lava flow and one of the largest amounts of tephra since the settlement of Iceland (lava: 1.3 km³ on an area of ​​65 km², tephra: 0.24 km³). The series of eruptions began on April 5, 1766 and lasted until May 1768. The areas Austur-Húnavatnssýsla and Skagafjördur as well as Rangárvellir, Land and Hreppar suffered, the poisonous Tephrafall harmed cattle and humans. Lava bombs flew up to 15-20 km, and the sudden melting of snow and ice on the slopes of the Hekla created lahars .

Eruptions in the 19th century and early 20th century

The volcano was in a long pause until it suddenly made a name for itself again on September 2, 1845:

“ After a violent storm on the night of September 2nd of this year, it was discovered in the Orkney Islands that the ground was covered with volcanic ash. So it was announced to the residents of Great Britain that Hekla (sic) had been active again. Accordingly, soon afterwards came the news of a major eruption on the mountain.

On the night of September 1, residents of the area were startled by a terrible rumble underground that lasted until noon the next day. Then, with an enormous crash, 2 large holes opened on the sides of the summit, from which poured lava flows that poured down over two gorges on the sides of the mountain. The whole summit was surrounded by clouds of steam and volcanic ash. The adjacent rivers became so hot that the fish in them died, and the sheep fled in horror from the nearby plateaus, some burned before they could escape.

On the night of September 15, two more craters opened - one on the eastern and the other on the western slope of the mountain - and lava flowed from both over the next 22 hours. It flowed up to a distance of about 36 km (20 miles), killing a lot of livestock and destroying pastureland. 36 km from the crater, the lava flow was still approximately 1.20 to 1.50 m (40-50 feet) deep and nearly 1.8 km (1 mile) wide.

On October 12th, a new lava flow came in and piled up similar amounts of lava. The mountain continued these activities until April 1846; then he paused for a while, only to start over the following October. Since then, however, he has been at rest.

The effects of these eruptions were catastrophic. The whole island was covered with volcanic ash, which, where it did not burn the grass directly, gave it a poisonous color. The cattle it ate were attacked by a moray eel and many animals died from it. The ice and snow that had accumulated on the mountain for a long time melted away completely because of the heat. Rocks weighing about half a ton were thrown 7-8 km (4-5 miles). "

- Anonymous, 1872

The eruption did not end until April 4, 1846. The tephra precipitation of 0.17 km³ was mainly E-SE, directly in the east the layer was 20–40 cm deep. Fine particles of the ash reached the Faroe Islands, the Shetland and Orkney Islands. The lava flows in the west and northwest covered an area of ​​25 km² with 0.63 km³ of lava. Such large quantities of ashes containing fluoride fell over the areas that the animals died two years later.

There were quite small eruptions between February 27, 1878 and April 1878 and on April 25, 1913 and May 18, 1913. Both came from crevices about 10 km east of the Hekla. the first produced 0.2 km³ of lava and thus covered 15.5 km². The second came from fissures at Mundafell and Lindafit, producing 3.8 and 6.3 km² of lava, respectively.

Eruptions in the 20th century and at the turn of the millennium

Around the middle of the 20th century, the Hekla volcano changed its eruption rhythm. The most recent outbreaks have occurred fairly regularly about every ten years (most recently in February 2000). The last of the 20th century occurred in 1947, 1970, 1980/81 and 1991. Ash clouds from the Hekla found their way to Helsinki in Finland. Traces have also been found in Germany. Volcanic bombs were found in Skálholt , about 50 km away .

1947-1948

The 1947 eruption began on March 29, 1947 and ended on April 21, 1948. It was a very powerful eruption (VEI 4). A lot of lava was produced here. The total volume was 0.8 km³. In addition, 0.21 km³ of tephra was emitted. The ashes fell in places such as England and Finland. The height of the volcano was 1,447 m before the eruption, then rose to 1,503 m before it got its current height of 1,491 m through erosion and collapse.

The first eruption phase

The 1947 eruption took place more than 100 years after the last eruption of the actual Hekla volcano, not counting smaller eruptions in the area whose ejected material differed from that of the Hekla. It was the longest dormant period of the volcano since 1104. Shortly before the eruption on March 29, 1947, nobody had noticed anything unusual on the mountain. At 6:41 ± 3 minutes the eruption began with great noise, the sounds of later eruptions were also heard in other parts of the country. An earthquake with a magnitude of 6 on the Mercalli scale occurred at 6:50 and the Heklugjá opened even more, so that the intensity of the eruption also increased and finally covered a 4 km stretch on the summit ridge.

In the first few hours it was a Plinian eruption , with pyroclastic currents also falling. At 7:08 am, the eruption cloud had reached a height of 30 km. It was initially carried to the southeast by the wind. Ash fell over the Fljótshlíð and Eyjafjallajökull district , turning the glacier black. Ash and rocks fell in Fljótshlíð until the layers were about 3–10 cm thick. For example, a lava bomb that fell 20 miles from Hekla was 0.5 m in diameter and weighed 20 kg. Sometimes even larger lava bombs were found. Rock debris with a circumference of 50 m fell up to 1 km from the eruption site.

The ashes fell on Helsinki 51 hours after the eruption began . The ash cloud had covered over 2860 km in that time.

The initial tephra production rate was 75,000 m³s ⁻¹ in the first 30 minutes and dropped to 22,000 m³s ⁻¹ in the next half hour . In this initial phase, a total of 0.18 km³ of tephra was produced, which corresponds to 4.5 × 10 ⁷ m³ of solid rock, and covered 3.130 km² of land and sea surface. Also lahars came 3 Ml, because of the melted snow and also directly from the summit column, after which the flow from the mountain Ytri-Rangá overflowed its banks.

In the first 20 hours of the eruption, 3,500 m³s ⁻¹ lava was ejected from a crevice , which divided into various lava flows and finally covered 12–15 km² of land. On the second day, eight columns of lava could be made out. A crater that formed at a height of 860 m was called Hraungígur (= German lava crater) and produced a steady flow of lava.

Another crater called Axlargígur (= shoulder crater) emitted a column of smoke with loud explosions every 10 seconds, creating visible pressure waves in the smoke.

From the fourth to the sixth day of the eruption, the intensity of the eruption visibly decreased and concentrated on the side and summit craters.

98 farms suffered damage from the eruption, but only two farms were abandoned as a result of the eruption. Many volunteers were called in to remove the ashes and rocks from buildings and other areas, about 1,000 man- days by the end of July.

Later eruptions

The explosive eruption intensified again from April 9th ​​to April 12th and then subsided again by April 28th. The Tephrafall lasted until June of that year. On September 21, the Axlargígur crater had a circumference of 960 m at its highest point, the circumference of the summit crater was 700 m at its highest point and towered over the summit ridge by 90 m. More craters formed during the following winter. The explosive phase ended after six months.

However, lava continued to flow from the Hraungígur crater. At the beginning the emission rate was 100 m³s ⁻¹ , then fell to 5–10 m³s ⁻¹ in April and at the beginning of May at a velocity of 20 cms ⁻¹ , which increased to 150 m³s ⁻¹ at the end of June and remained so until July with a maximum speed of 2 to 2.5 ms ⁻¹ . From then on it fell to 10 m³s ⁻¹ in November. The lava initially contained 57–58% SiO ₂ and 11% Fe ₂ O ₃ , later this changed to 54% SiO ₂ and 13.5% Fe ₂ O ₃ . Some of the lava moved in lava tunnels before returning to the surface. Their front was up to 15 m high. On June 15 and 16, a lava flow south of the Melfell mountain flowed at a speed of 1 km in 30 hours. It stopped and cooled down on June 21st. 7.8 km from Hraungígur crater. The longest lava flow from this eruption was 8 km long and stopped in Stóraskógsbotnar . A scientist who was filming one of the lava flows on November 2nd was hit by a block of lava and killed. The lava eruption stopped on April 21, 1948 after 13 months, after it had covered 40 km² with lava at a maximum depth of 100 m. The lavas were mainly 'A'ā -Laven, with some areas of Pāhoehoe -Lava or ropy.

Fine dust and volcanic ash darkened the sky over Iceland and especially in the area around the volcano in May and June of the year. The sheep became sick from the fluorine that had poisoned the pastures. In April and May 1948, 24,000 tons of CO _{2 were} degassed in some depressions near the Hekla. 15 sheep and some wild animals and birds were killed. Trenches were dug to drain these lowlands and CO ₂ emissions stopped at the end of the year.

1970

The 1970 outbreak of Hekla began at 9:23 a.m. on May 5 and continued through July 5. It was not a very significant outbreak (VEI 3). It produced 0.2 km³ of lava , which covered an area of ​​18.5 km², and 6.6 × 10  ⁷ m³ of tephra , which covered an area of ​​40,000 km², mainly in the northwest of the volcano. At the summit fissure Heklugjá there was an eruption only in a certain area at the extreme southeastern end. Most of the eruption occurred at other nearby crevices. The main eruption stopped in SSW on May 10th and in Hlíðargígar craters on May 20th, but a new fissure opened and ejected lava by July 5th. This lava consisted of an andesite - olivine mixture similar to that of the later phase of the 1947 eruption.

The initial stages of the eruption

Before the eruption, the volcano initially heated up and more snow melted than is normal at this time of the year. At 8:48 p.m. on the evening of the eruption, earthquakes with a magnitude of up to 4 on the Richter scale began . The eruption itself started rather weakly at 9:23 pm ± 2 min and later gained strength. At 9:35 p.m., the first precipitation of rock fragments and ash was found at the Búrfell power station , which is 15 km from the Hekla. Thereupon the local population was evacuated.

The eruption began in two places, one in the southwest of the Axlargígur crater and the other below the Hraungígur . At 10:30 p.m., a crater at a height of 780 m produced a lava fountain that was approx. 1000 m high. During the night an almost equally high lava fountain (700 m) was visible from the main crater. A 500 m long crevice opened below the Hraungígur, creating more lava fountains and streams. An hour later the next fissure opened, this time in the northeast, and it too produced 2 lava fountains. Then a third column appeared, throwing out 500 m high lava fountains. At midnight a fissure opened in the northwest of the Hraungígur, through which a 300 m long lava fountain rose 300 m into the air. At midnight the new lavas covered over 1 km² and expanded this area to 7.5 km² by morning, which means a flow velocity of 1500 m³s ⁻¹ .

During the first two hours, tephra was formed at a rate of 10,000 m³s ⁻¹ . The eruption column had reached 16,000 m at 10:10 p.m. and caused a loud thunderstorm . The ashes were carried north by the wind, with the sky turning black in places. In the village of Blönduós, 190 km away, it rained ash from midnight to 2 a.m. She reached a trawler at sea 330 km north of Iceland. Residents put plates in front of the house to collect the Tephrafall. It was found that the ashes had only fallen on a narrow strip of land, where eight tons per hectare fell.

Later eruption in 1970

At 5:30 a.m. on May 6, the lava flow was four kilometers long. Many lava bombs were found around the main crater, one was six square meters and probably weighed twelve tons. Around two percent of the materials produced by the craters consisted of xenolites . These in turn are made up of various types of rock such as basalt , andesite , ignimbrite and sedimentary rocks .

On May 12, the eruption at Skjólkvíar became stronger with up to 2,500 m high columns of steam. The intensity then decreased more and more until this outbreak finally came to a standstill on May 20th. At the time, the lava field covered 5: 8 km². Later that day, however, a 900 m long crevice opened 1 km north of the main crater of the Hlíðargígar crater group. At this point 17 lava fountains could be seen the following night, which reached heights of 20 to 50 m. By the evening of the next day a new row of 10 to 12 craters had formed, which hurled pieces of cinder 50-100 m high into the air. The series of craters was later called Öldugígar . Gradually fewer and fewer craters were active. The most active crater formed a cone that towered over the ridge on which the row of craters had formed by 100 m. Lava continued to flow from its base until mid-June when the lava eventually made its way through the northern rim of the crater. The larger craters produced more tephra. On July 5, the eruption stopped.

consequences

During Hekla outbreaks, fluorine is always formed , which bonds with the surface of ash particles. Even thin particles can have a fluorine content of 350 ppm. Even an intake of 25 ppm is enough to cause fluorine poisoning in sheep . If the sheep ingest 250 ppm with the feed, it will be fatal within a few days. 79% of Iceland's sheep were killed in this way in 1783, presumably as a result of fluorine poisoning from the Laki crater eruption . Some of the ash produced at that time had a fluorine content of 0.2%; two days after the eruption, the affected grass had a dry weight fraction of up to 0.4%.

1980 and 1981

17th to 20th August 1980

Outbreak of Hekla in 1980

The outbreak of 1980 was a weaker eruption (VEI3). It began at 1:28 p.m. on August 17, 1980 and lasted until August 20. It turned out to be a mixed eruption that produced lava 0.12 km³ and tephra 5.8 × 10 ⁷  m³. The summit crevice opened over a length of 7 km. Shortly before the eruption began, a column of steam formed and eventually the column of eruption reached a height of 15 km. Most of the Tephra Falls were towards the NNE and lasted for about 2 hours. The layers were 20 cm thick at a distance of 10 km from the summit and <1 mm at the coast at a distance of 230 km. The source of the lava was initially near the summit, then spread to other parts of the eruption fissure until, after 24 hours, the lava covered an area of ​​22 km². The last slag was seen on the morning of August 20th. This eruption was very unusual, partly because of the short time that had elapsed since the last eruption and partly because of its short duration. The previous outbreaks had lasted at least 2 months to 2 years each, instead of just 3 days as in this case.

April 9-16, 1981

The 1981 eruption, commonly viewed in science as a continuation of the 1980 eruption, began on April 9 at 3:00 pm and lasted until April 16, 1981. It was weaker than the previous one (VEI2) and predominantly effusive. 3 × 10 ⁷  m³ of lava formed in the process. Three lava flows emanated from a new crater at the summit and reached a distance of 4.5 km from the volcano, while at the same time extending over 5–6 km².

1991

Liquid lavas (Pahoehoe)

A moderate eruption (VEI 3) occurred from January 17, 1991 to March 11, 1991. 0.15 km³ of lava and 2 × 10 ⁷  m³ of tephra formed .

This eruption, accompanied by a strong smell of sulfur and earthquakes , began as the Plinian eruption . The eruption column reached a height of 11,500 m after only 10 minutes. It was moving towards the coast at a speed of about 70 km / h (which one ??). The eruption quickly turned into an effusive phase and andesitic lava emerged, with the lava flows finally covering an area of ​​23 km² at an average depth of 6 to 7 m. At the beginning there were up to 300 m high lava fountains on the Heklugjá , the main eruption fissure on the summit of the Hekla, and other fissures. On the second day this activity stopped, except for the one in the Heklugjá Fissure , where the main crater was formed. During these two days, 800 m³s ⁻¹ lava formed. This low viscosity , i.e. H. Thin lava had a silicate content (SiO ₂ ) of about 54%.

2000

New Hekla lavas from 2000 (photo from July this year)

This eruption was rather short, it started on February 26, 2000 and lasted until March 8 of the same year. This was a moderate breakout of strength VEI-3. It was this lava in a volume of 0,189 cubic kilometers ejected and 10 ⁷  m³ Tephra . The risk of fluorine poisoning in this outbreak was rated as low because Iceland has the largest number of sheep in the stables in winter.

Four eruption phases can be identified: initial explosive stage, fountains of fire, Strombolian eruptions, formation of lava flows (effusive stage).

The eruption began on February 26, 2000 at 6:19 p.m. local time. As usual, he announced himself with a series of earthquakes on a low frequency when the Hekla erupted. At the time mentioned above, the first signs of an eruption cloud could be seen. Since the devices for measuring the expansion of the earth's crust (strain meter ) substantiated the suspicion of an imminent eruption, the volcanologists issued a warning to civil defense, which was broadcast on the radio about 15 minutes before the actual start of the eruption. It already peaked in the first hour of the outbreak. After the first night, the Heklugjá eruption fissure had opened over a length of six to seven kilometers at the summit and tongues of fire could be seen floating over it.

The eruption column made of steam, ash and rock material reached a height of almost 15,000 meters, the ash was carried to the island of Grímsey , 300 km away, north of Iceland . A NASA plane happened to fly 36 hours after the beginning of the eruption through the eruption cloud and it was possible to make a number of measurements about its composition.

On February 27th, lava flows were mainly observed. On February 28, lava production stopped with reduced strength. Strombolian eruptions were found in three of the craters. On February 29, strong northerly winds favored ash fall over the Fljótshlíð district . The lava flows on the northeast flank were so cold in the evening that you could walk on them. During an observation flight on March 1, strong activity was observed in three craters on the SW slope of the Hekla, while the southern end of the Heklugjá seemed largely calm and only the northern end was still shrouded in smaller clouds. On March 2, activity increased again in the summit craters. From March 6, the eruption activity then gradually subsided, to finally dry up on March 8.

Current developments in 2011

In May 2011, researchers from the University of Iceland in Reykjavík discovered a bump 20 kilometers wide. Then magma rose underground to a depth of 14 to 20 kilometers and pushes the soil upwards. Since the last eruption in 2000, Hekla has lifted five millimeters per year according to satellite measurements. Inclinometers on the mountain also show that the Hekla has now expanded more than before its last eruptions in 2000 and 1991. There is no comparable data from the previous eruptions in 1980 and 1970.

Pyroclastic currents on the Hekla

The majority of scientists had assumed by the year 2000 that Hekla was not able to produce the most dangerous phenomenon of volcanism, namely pyroclastic currents . In January 2003, however, a team from the Geological Institute of the University of Iceland (Norvol Institute) headed by Dr. Ármann Höskuldsson states that they found traces of such a pyroclastic flow on the sides of the volcano. It was about 3 miles long.

In the meantime, the scientific point of view has changed in this regard; it is assumed, for example, that small pyroclastic currents generally form in the explosive phase of the Hecla eruptions.

For civil protection, this means that if there is a risk of an eruption, people should keep a greater distance from the volcano than previously assumed.

Vegetation on the Hekla

Plant growth in general

Stalkless catchfly

Inflated catchfly

Mosses at Landmannahellir in the area of ​​influence of the Hekla

The immediate surroundings of the volcano range from heights of less than 200 m in the valleys of the Ytri-Rangá and Þjórsá rivers up to around 1491 m to the summit of the Hekla. However, vegetation levels like in the Alps are not known here.

In contrast, the various forms of erosion , not least that caused by the eruptions of the volcano, shape the landscape and its vegetation. As in many areas in the interior of Iceland, the subsoil is very porous , so it cannot hold the rainwater well on the surface. It seeps away quickly, so it is called an " endaphic " one. H. desert caused by the soil. Around the Hekla there is a barren desert of lava and tephra with very little vegetation. The latter is also limited by the considerable northern latitude - Hekla is almost exactly at the 64th parallel.

The few plants that can be found on the Hekla, such as the puffed up cucumber (Silene uniflora) keep themselves alive with a widely branched root system that can hold the necessary water. More encountered here plants include the thrift ( Armeria maritima ), the Arctic thyme ( Thymus arcticus ), the Norwegian chickweed ( Arenaria norwegica ) or about the sand cress ( Cardaminopsis petraea ). Cushion-shaped plants such as the stemless catchfly ( Silene acaulis ) are also found. Moosheiden or Moostundren can be found on older lava fields of the Hekla, for example in some places on the slopes of Dómadalsleið and Fjallabaksleið nyrðri , where the gray and wooly serrated moss ( Rhacomintrium sp .) Dominate .

Higher plants can only seldom penetrate a thick layer of moss, but some typical species can now and then prevail: early flowering thyme ( Thymus praecox ), black crowberry ( Empetrum nigrum ), common carnation ( Armeria maritima ), stalkless cucumber ( Silene acaulis ), Knöllchenknötrich ( Polygonum viviparum ), sourling ( Oxyria digyna ) and herb willow ( Salix herbacea ) (WISNIESKI 1999). The age of the lavas can also be roughly estimated from their vegetation. One finds dense moss vegetation, for example, on the lavas from the eruptions of 1766 and 1845. In higher altitudes, one only comes across lichens .

Settlement of plants after an outbreak

Plants are covered by lavas or tephra during outbreaks. Some die, but others look for a new way to the top of the terrain. This could be seen on the northwest side of the volcano in summer 2001. Under a 15 cm thick layer of tephra from the 2000 eruption, the soil horizon from before 2000, which was still heavily interspersed with roots and remains of vegetation, was found. At these points, buried parts of plants such as the herb willow ( Salix herbacea ) had made their way upwards. After only 1 ½ years after the eruption, numerous vegetation islands can be found on the young surface. The first mosses settle, as has been found, already 20 years after the last eruption and after 50 years already form a uniform blanket of up to 20 cm thick.

The Hekluskógar project

In the Middle Ages the area around Hekla was still wooded. You can recognize this by names such as Stóraskógsbotnar (for German lowlands of the great forest , see the eruption of 1947). Forests, like certain grasses, are actually more resistant than other vegetation when it comes to ash fall, for example. But in the case of the Hekla area, similar to other areas of Iceland, there was overgrazing and other excessive use by humans (firewood, house building and coal production, etc.) The State Reforestation Society ( Skógræktar ríkisins ) therefore has to prevent erosion, founded the Hekluskógar project. On a 90,000 hectare area at the foot of the volcano, people began to fertilize the soil and sow grass. Then they want to plant a forest on about 60% of the area. It is supposed to hold on to the ashes and thus prevent wind erosion and sandstorms, as well as frost and water erosion. The forest will thus also serve biodiversity . The aim is to restore the original birch and willow forests in order to prevent erosion.

Ascent

On the slope of the Hekla

The first ascent was (probably) achieved in 1750 by Eggert Ólafsson and Bjarni Pálsson . On June 30, 1845, the Austrian writer Ida Pfeiffer climbed the volcano. An ascent is easiest via the north or north-west flank. The climb begins from the slopes Landmannaleið west of the lava field Nýjahraun the crater Rauðaskál and is about 14 km long.

Sights in the area

Gjáin

Not far from the Hekla is the historic Stöng farm , which was destroyed in a volcanic eruption in 1104 and has since been dug up again and rebuilt nearby ( Þjóðveldisbær ). The Háifoss waterfalls and the Gjáin gorge are not far from Stöng. There is a small museum on Hekla at the Leirubakki farm . The mountain is close to the Landmannalaugar nature reserve .

Trivia

• The Boeing 757-200 of Icelandair with the flag TF-FIU is named after the volcano.
• The lava of Hekla is used as a trituration in homeopathy. A minimum content of 50 percent silicon dioxide and 18 percent iron (III) oxide is required in the corresponding monograph .

See also

• Volcanoes in Iceland
• List of mountains and elevations in Iceland
• History of Iceland

literature

• Thorarinsson, Sigurdur: Hekla, A Notorious Volcano. Reykjavík, Almenna bókafélagið, 1970

Web links

Wiktionary: dra åt Häcklefjäll  - explanations of meanings, word origins , synonyms, translations

Commons : Hekla  - collection of images, videos and audio files

Scientific contributions to Hekla

Overarching presentations

• Hekla in the Global Volcanism Program of the Smithsonian Institution (English)
• Institute Of Earth Sciences, Univ. Iceland: Hekla volcano (short description) (English)
• "Fire at the gate to hell". The volcano Hekla. Article on scinexx.de
• Guðrun Larsson: Field Trip 05: Hekla, 2008 (English) ( Memento of 19 July 2013, Internet Archive ), from the International Association of Volcanology and Chemistry of the Earth's Interior issued fieldwork preparation with many general information about the volcano
• Morales: Hazard Assessment and Risk Mitigation for Tourists at Hekla Volcano . University of Iceland 2010 (PDF)

To the magmatic system of Hekla

• Séverine Moune, et al .: Recent volatile evolution in the magmatic system of Hekla volcano, Iceland , Earth and Planetary Science Letters 255 (2007) 373–389 (PDF, English)
• Ronni Grapenthin, et al .: Surface loading affects internal pressure source characteristics derived from volcano deformation signals , Univ. Alaska, Institute for Earth Sciences (2010) (PDF, English; 4.3 MB)
• Erik Sturkell, et al .: New insights into volcanic activity from strain and other deformation data for the Hekla 2000 eruption , Journal of Volcanology and Geothermal Research 256 (2013) 78-86 (PDF, English)
• Stefanie Hautmann, et al .: Magma buoyancy and volatile ascent driving autocyclic eruptivity at Hekla Volcano (Iceland) , Geochemistry, Geophysics, Geosystems 18 (2017) 3517-3529 (PDF, English)

Geophysical monitoring devices

• Strainmeter at the Hekla, IMO (English)

Individual evidence

1. ↑ Cf. Sigurður Þorarinnsson: Hekla. A notorious volcano. Reykjavík, 1970, p. 6.
2. ^ Haukur Jóhannesson, Sigmundur Einarsson: Hekla, fjall með fortíð.
3. ↑ ^{a b} Ari Trausti Guðmundsson : Íslensk fjöll. Gönguleiðir á 151 tind. Reykjavík, 2004, p. 94.
4. ^ Eggert Pálsson in the booklet of the CD Hekla and other Orchestral Works published by BIS
5. ↑ Erik Sturkell: Hekla, en helvetes volkan , Veðurstofa Íslands (Iceland's meterologiska institut), Reykjavík. Dictionary: dra åt Häcklefjäll
6. ↑ ^{a b c} Thor Thodarsson, Armann Hoskuldsson: Classic Geology in Europe Iceland third. 2002, pp. 87f
7. ↑ Erik Sturkell, Kristján Ágústsson, Alan T. Linde, Selwyn I. Sacks, Páll Einarsson: New insights into volcanic activity from strain and other deformation data for the Hekla 2000 eruption . In: Journal of Volcanology and Geothermal Research . tape 256 , April 2013, p. 78-86 , doi : 10.1016 / j.jvolgeores.2013.02.001 .
8. ↑ ^{a b} Agust Gudmundsson, Niels Oskarsson, Karl Gronvold, Kristjan Saemundsson, Oddur Sigurdsson: The 1991 eruption of Hekla, Iceland . In: Bulletin of Volcanology . tape 54 , no. 3 , February 1992, ISSN  0258-8900 , p. 238-246 , doi : 10.1007 / BF00278391 .
9. ↑ ^{a b c d} Ármann Höskuldsson, Níels Óskarsson, Rikke Pedersen, Karl Grönvold, Kristín Vogfjörð: The millennium eruption of Hekla in February 2000 . In: Bulletin of Volcanology . tape 70 , no. 2 , November 23, 2007, ISSN  0258-8900 , p. 169-182 , doi : 10.1007 / s00445-007-0128-3 .
10. ^ S. Thorarinsson: Hekla, A Notorius Volcano p. 18
11. ↑ Erik Sturkell: Hekla Deformation . Geological Institute, University of Iceland. Accessed April 13, 2009 (English).
12. ↑ ^{a b} S. Thorarinsson: Hekla, A Notorius Volcano, pp 39-58.
13. ↑ Geological Institute. University of Iceland: Hekla.
14. ↑ Heidi Soosalu: Hekla Seismicity. University of Iceland.
15. ↑ Monitoring the Hekla: https://en.vedur.is/about-imo/news/monitoring-hekla
16. ↑ ^{a b} Stefanie Hautmann, I. Selwyn Sacks, Alan T. Linde, Matthew J. Roberts: Magma buoyancy and volatile ascent driving autocyclic eruptivity at Hekla Volcano (Iceland) . In: Geochemistry, Geophysics, Geosystems . tape 18 , no. 9 , September 2017, p. 3517-3529 , doi : 10.1002 / 2017GC007061 .
17. ↑ T. Thordarson, G. Larsen: Volcanism in Iceland in historical time: Volcano types, eruption styles and eruptive history . In: Journal of Geodynamics . tape 43 , no. 1 , January 2007, p. 118–152 , doi : 10.1016 / j.jog.2006.09.005 .
18. ↑ ^{a b c d} Hekla eruption 2000. Institute of Earth Sciences, University of Iceland. (English)
19. ↑ Eiríksson, Jón; et al .: Chronology of late Holocene climatic events in the northern North Atlantic based on AMS 14C dates and tephra markers from the volcano Hekla, Iceland . Journal of Quaternary Science 15 (6) , 2000, pp. 573-580. doi : 10.1002 / 1099-1417 (200009) 15: 6 <573 :: AID-JQS554> 3.0.CO; 2-A
20. ↑ Baillie, Mike: Hekla 3: how big was it ?. Endeavor. New series 13. 1989, pp. 78-81
21. ↑ Baillie, Mike: Do Irish bog oaks date the Shang dynasty ?. Current archeology 10, 1989, pp. 310-313
22. ^ Baker, Andy, et al .: The Hekla 3 volcanic eruption recorded in a Scottish speleothem ?. The Holocene 5 (3) , 1995, pp. 336-342. doi : 10.1177 / 095968369500500309 .
23. ^ Dated by uranium-thorium thermal ionization mass spectrometry to 1135 ± 130 BC in Baker, Andy; et al .: The Hekla 3 volcanic eruption recorded in a Scottish speleothem ?. The Holocene 5 (3) , 1995, pp. 336-342. doi : 10.1177 / 095968369500500309 .
24. ↑ Dugmore, AJ; GT Cook, JS Shore, AJ Newton, KJ Edwards and G. Larsen: Radiocarbon Dating Tephra Layers in Britain and Iceland. Radiocarbon 37 (2), 1995. online
25. ↑ Andrew Dugmore, Geriant Coles, Paul Buckland: A Scottish speleothem record of the H-3 eruption or human impact? A comment on Baker, Smart, Barnes, Edwards and Farrant. The Holocene 9.4 , 1999, pp. 501-503
26. ↑ Yurco, Frank J .: End of the Late Bronze Age and Other Crisis Periods: A Volcanic Cause . in Teeter, Emily; Larson, John (eds.): Gold of Praise: Studies on Ancient Egypt in Honor of Edward F. Wente. Studies in Ancient Oriental Civilization. 58. Chicago, IL: Oriental Institute of the Univ. of Chicago. 1999, pp. 456-458. ISBN 1-885923-09-0
27. ↑ Stefan WastegÅr: TOWARDS A HOLOCENE TEPHROCHRONOLOGY FOR SWEDEN. XVI INQUA Congress, Paper No. 41-13, Saturday July 26, 2003
28. ↑ mainly based on: Sigurður Þórarinnsson: Heklueldar. 1968 as well as http://wayback.vefsafn.is/wayback/20041027195856/www.islandia.is/hamfarir/jardfraedilegt/eldgos/hekla.html and eruption history overview Smithsonian Inst. In the Global Volcanism Program of the Smithsonian Institution (English), access: 20 . May 2013
29. ^ University of Iceland . Retrieved April 13, 2007.
30. ^ ^{A b} S. Thorarinsson, Hekla, A Notorius Volcano. P. 11.
31. ↑ ^{a b c d e f g h i j k l m n} tab "Eruptive History" in: Hekla in the Global Volcanism Program of the Smithsonian Institution (English)
32. ↑ ^{a b c} S. Thorarinsson: Hekla, A Notorius Volcano, S 14 f.
33. ^ Hekla Eruption History. Volcano World.
34. ↑ Own translation from English. - Anonymous. Wonders of Creation: A descriptive account of volcanoes and their penomena.
35. ↑ Cf. Sigurður Þorarinnsson: Hekla. A notorious volcano. Reykjavík 1970, p. 17.
36. ^ Ari Trausti Guðmundsson: Land im Werden. An outline of the geology of Iceland. Reykjavík 1996, p. 94.
37. ^ Thorarinsson: Hekla, A Notorious Volcano , pp. 19-38
38. ↑ ^{a b c d} Thorarinsson: Hekla, A Notorious Volcano , p. 39-58
39. ↑ Hutchinson, IP: Upphaf Eldgossins í Heklu, 1980 (On the Eruption of Hekla, 1980) ( Icelandic and English , PDF; 2.4 MB) In: Náttúrufræðingurinn 52 (1-4) . Pp. 175-183. Archived from the original on October 1, 2007. Retrieved January 1, 2008.
40. ↑ The Hekla Eruption of 1991
41. ^ Cf. “The eruption-related seismicity starts only 30-80 minutes before its onset. Hundreds of small volcano-tectonic earthquakes (magnitude <3), related to the intrusion of magma, occur during the first hours, when the eruption is violent and explosive. " online access: April 14, 2009.
42. ↑ For the mode of operation of such a device (strain meter) see: http://jan.exss.de/en/da_ Wirkweise.html
43. ↑ Hekla erupts Feb. 26-29, 2000 . In: turdus.net . Retrieved April 14, 2009.
44. ↑ T. Campbell, OPMills, CM Riley, WI Rose: Ash? Particles Found Inside the NASA DC8 which Encountered Hekla's February 2000 Stratospheric Volcanic Cloud - a Needle in a Haystack. American Geophysical Union, Fall Meeting 2001, abstract # V42D-1060, bibcode : 2001AGUFM.V42D1060C
45. ↑ Hekla 2000. Institute of Earth Sciences, University of Iceland http://wayback.vefsafn.is/wayback/20050622000000/earthice.hi.is/page/hekla27feb2000
46. ↑ Hekla 2000. Institute of Earth Sciences, University of Iceland http://wayback.vefsafn.is/wayback/20110329143900/earthice.hi.is/page/hekla28feb2000
47. ↑ Hekla 2000. Institute of Earth Sciences, University of Iceland http://wayback.vefsafn.is/wayback/20110329144008/earthice.hi.is/page/hekla29feb2000
48. ↑ Hekla 2000. Institute of Earth Sciences, University of Iceland http://wayback.vefsafn.is/wayback/20110329143817/earthice.hi.is/page/hekla1mars2000
49. ↑ Hekla 2000. Institute of Earth Sciences, University of Iceland http://wayback.vefsafn.is/wayback/20110329143804/earthice.hi.is/page/hekla2mars2000
50. ↑ Deep magma storage at Hekla volcano, Iceland, revealed by InSAR time series analysis. Retrieved July 8, 2011 . 
51. ↑ See e.g. B. Guðrun Larssen, Rhian Meara: IAVCEI General Assembly. 2008 Iceland. Field Trip 5: Hekla Volcano, p. 10, http://www.iavcei2008.hi.is/Apps/WebObjects/HI.woa/swdocument/1013922/Field+Guide+-+Hekla.pdf ( Memento from July 19, 2013 in the Internet Archive )
52. ↑ ^{a b} Andreas Kellerer-Pirklbauer: The volcano Hekla on Iceland - a geoscientific short portrait of a highly active mountain of fire . University of Graz. January 3, 2003, abstract
53. ^ NA Cutler, LR Belyea, AJ Dugmore: Spatial patterns of microsite colonization on two young lava flows on Mount Hekla, Iceland. In: Journal of Vegetation Science. 19, 2008, p. 277, doi : 10.3170 / 2008-8-18371 .
54. ^ High-latitude vegetation dynamics: 850 years of vegetation development on Mt Hekla, Iceland (abstract)
55. ↑ Hekluskógar project ( Memento of the original from September 24, 2013 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. 
56. ↑ The Hekluskogar idea ( Memento of the original dated February 7, 2009 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. (English) 
57. ↑ Ida Pfeiffer: Journey to the Scandinavian north and the island of Iceland in 1845 . 1st edition. tape 2 . Publishing house by Gustav Heckenast, 1846, p. 41 ff .
58. ↑ Hekla lava e lava . In: Homeopathic Pharmacopoeia 2019 .