Askja

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Askja
Askja.jpg
height 1510  m
location Iceland
Mountains Dyngjufjöll
Coordinates 65 ° 1 ′ 48 ″  N , 16 ° 45 ′ 0 ″  W Coordinates: 65 ° 1 ′ 48 ″  N , 16 ° 45 ′ 0 ″  W
Askja (Iceland)
Askja
Type Stratovolcano
rock Basalt and rhyolite
Last eruption 1961 (active)
Caldera of the Askja volcano with Víti crater in the foreground and Öskjuvatn in the background

Caldera of the Askja volcano with Víti crater in the foreground and Öskjuvatn in the background

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Direction of the ash rain of 1875
Drekagil Gorge

The Askja is a volcano north of Vatnajökull in Iceland ; As a central volcano, it dominates the approx. 200 km long volcanic system of the same name .

The volcano is now part of the Vatnajökull National Park .

Surname

The name of the volcano refers to the Icelandic word askja , which means "box" in common language, but " caldera " in geological language .

Askja central volcano

The volcano is composed of at least three nested calderas (approx. 45 km²), which together form the Dyngjufjöll mountain range. In the middle of the most recent caldera, created in the volcanotectonic episode of 1875, is Lake Öskjuvatn , one of the deepest lakes in Iceland at 220 m. The smaller Víti crater , also filled by a lake, is located in the caldera. The oldest documented caldera formation took place around 8910 BC. Instead of.

The Askja rises up to 800 m above the surrounding plateaus and at Þorvaldstindur , on the edge of the caldera in Dyngjufjöll, reaches a height of 1510 m.

Askja volcanic system

Caldera lake Öskjuvatn, Dyngjufjöll in the background
View from Dettifoss to the Jökulsárgljúfur gorge with a series of craters belonging to the Askja system in the background; it crosses the gorge at Hafragilsfoss
At Hrossaborg, Herðubreið on the left in the background

The central volcano dominates an approx. 200 km long system of fissures oriented from southwest to northeast. To him z. B. the shield volcano Kollóttadyngja .

expansion

The volcanic system extends from the central volcano Askja itself, which is about 40 km southwest of the Herðubreið tabular volcano and the Herðubreiðarlindir oasis , over 150 km north to the Melrakkaslétta peninsula . At the same time, it is about 30 km from the central volcano to the south.

With a total length of approx. 200 km but a width of less than 20 km, it is the longest volcanic system in Iceland , according to T. Thordarson . However, other researchers have restricted the total length to 120 or 170 km, depending on whether one wants to see a northern apparent break as its end or as a gap in it.

Various associated craters and volcanic mountains

The system of Askja include for example the Tuya Herðubreið , the subglacial mound Herðubreiðartögl and the shield volcanoes Kollóttadyngja , Flatadyngja and Svartadyngja .

The craters of the Sveinagraben (Isl. Sveinagjá ) are located approx. 50 km north of the central volcano, parallel to the Fremrinámur volcanic system . There are other craters near the Dettifoss waterfall .

Also part of the system is the Hrossaborg ash crater directly south of Hringvegur , about 20 km east of Námafjall . It was formed in a large hydromagmatic eruption about 7,000 years ago.

Eruption story

Prehistoric eruptions

There is evidence of volcanic activity on the Askja that goes back several hundred thousand years.

Larger basalt eruptions in the Holocene were the Gígöldur and eruptions that created the Holuhraun and Þorvaldshraun lava fields .

Apart from the large caldera-forming eruption around 8500 BC. In the southeast of the central volcano can be found around 2050 BC. Chr. Z. B. prove eruptions on the Flatadyngja and in other areas in the northeast of the central volcano, which contain explosive and effusive phases, including the formation of a lava lake; Similar phenomena are found around 1250 BC. Chr., Whereby this time the activity was concentrated on the central volcano and Litladyngja. In both cases, eruptions on a main crater as well as on fissures further away can be proven.

Eruptions after settlement and formation of the youngest caldera

Since the settlement up to the end of the 19th century, two eruptions are suspected in the Askja system (1300 and 1797), but neither of them has yet been precisely proven.

The Askja fire

A long-lasting volcanic tectonic episode began on the Askja in 1874. It lasted intermittently until 1929, contained rift episodes, effusive and explosive eruptions both on the central volcano and on more remote parts of the volcanic system and was known as the so-called Askja fire .

The youngest caldera of the Askja as well as the smaller Víti crater were formed in a Plinian eruption in March 1875 .

As early as February 1874, clouds of steam could be seen over the mountain range of the remote Dyngjufjöll. In December of the same year a series of violent earthquakes shook the area, which was also noticeable in the populated areas. In January 1875, columns of smoke and fire were recognized. The basaltic lava field Holuhraun may have originated from this mostly effusive phase .

In February 1875 some people from the Mývatn area drove to Askja. There they saw spring springs of mud in the southeast of the caldera, but no real volcanic eruption. However, the ground there had sunk ten meters.

Only three days later, an effusive eruption started at Sveinagraben . This is a 30 km long trench system 50 km north of the central volcano. During the eruptions that lasted for several months, approx. 0.2–0.3 km³ of lavas were produced there.

On March 29, 1875, the beginning of the main explosive phase is to be set. As a result of a Plinian eruption, it rained ash over East Iceland from 3:30 am. When the Danish geologist Frederik Johnstrup came to the eruption site in the summer of 1876 , he realized that a magma chamber here had collapsed after it had emptied. Another smaller caldera had formed in the existing one with the dimensions 4580 × 2500 m, the lowest point of which was 238 m below the bottom of the main caldera. The volume of the collapse crater is about two cubic kilometers, more than twice that of the erupted rock, which suggests that a considerable part of the magma is still present as intrusions in the caldera walls or elsewhere in the volcanic system.

Shortly afterwards, the Maar Víti formed in a hydromagmatic eruption .

As a result, it turned out that it was the second or third strongest explosive volcanic eruption since the beginning of settlement in Iceland (after Hekla 1104 and Öræfajökull 1368). The ash rain was so heavy , especially in the east fjords , that pastureland was poisoned for a long time and numerous people emigrated, especially from the already difficult to settle area of Jökuldalsheiði . The volcano was practically unknown before.

The same volcanotectonic episode includes eruptions in the Askja volcanic system between 1920 and 1930. There were five individual series of eruptions at ring-shaped crevices around the Askja caldera and one fissure eruption at a six-kilometer-long fissure on the southern edge of the central volcano, which produced the Þorvaldshraun lava field . These eruptions were mainly effusive and took place in two phases: from 1921 to 1923 and from 1926 to 1930. The result was the lava fields Bátshraun (Austurfjöll), Mývetningarhraun, Kvíslahraun and Suðurbotnahraun . During the second eruption phase, u. a. a cinder cone in Lake Öskjuvatn and the Þorvaldshraun lava field .

In the 1960s

The last series of outbreaks to date occurred in the 1960s. From October 26, 1961 to November of the same year, new craters built up and created the Vikrahraun lava field . The craters are located in a 0.6 km long west-east-facing fissure on the east side of the Askja Caldera. At the beginning of the effusive eruption, 500 m high lava fountains were seen. The product, an Aa lava field , covered six square kilometers. It was expanded to eleven square kilometers by pahoehoe lavas .

Recent developments

A sinking of the magma chamber was observed from 1988 to 2007.

However, since 2007 it seems to have been filling up again. Magma accumulations are believed to be around three kilometers deep, which could indicate a new active phase. The earthquake activity has increased.

On the night of July 23rd to 24th, 2014, a landslide occurred in which an approx. 1 km wide section of the crater wall came loose; an estimated 50 million m³ of rock slipped off and triggered several 50 m high tsunamis in Öskjuvatn , which even reached the neighboring crater lake Víti . Destabilization of the subsoil due to a strong thaw is suspected to be the trigger.

NASA astronaut training

As part of the Apollo program, which led NASA in the 1960s, various geological excursions (Engl. Geologic field trips , short gfts) by, from those in Iceland on the brink of Askja and near two Krýsuvík on the Reykjanes Peninsula were denied . The first excursion took place from July 12th to 16th, 1965 and concerned the first three astronaut groups, the second excursion concerning astronaut groups four and five, including the later first man on the moon Neil Armstrong , was from July 2nd to 8th Completed in 1967. The aim of the excursions was on the one hand to introduce the astronauts to geological concepts and thus prepare them as best as possible for the geology likely to be encountered on the earth's satellite, and on the other hand to train the crews for specific lunar missions in a targeted manner. The so-called Moon Game was also completed, an exercise with the purpose of simulating staying on the moon and collecting representative samples from the environment. In the appendix of the official NASA documentation it says about the excursions in Iceland:

"Probably the most moon-like of the field areas."

"Probably the most moon-like of the excursion locations."

- Glen E. Swanson : Apollo Geology Field Exercises

Both excursions were led by Icelandic geologists Sigurður Thórarinsson and Guðmundar Signaldson.

German researchers at Askja

The Knebel and Grumbkow expeditions

Monument to von Knebel and Rudloff

In 1907 two Germans had an accident during an expedition on Öskjuvatn . It was the natural scientist Dr. Walter von Knebel and the painter Max Rudloff , both from Berlin. Both have been officially missing since July 10, 1907, as their bodies were never found.

The only survivor and thus the person responsible for the small expedition, the geology student at the time, Hans Spethmann , who at the time of the incident was doing research far away from the Öskjuvatn disaster in Askja, could no longer find the two researchers and the boat after returning to the base. He accompanied the search expedition immediately initiated by the Icelandic authorities to Askja at the beginning of August to clarify the fate of his companions. The search for them was unsuccessful.

The fiancé Knebels, Ina von Grumbkow , started a new search expedition to Askja in July 1908 together with the Berlin geologist Hans Reck in order to find out more about the mysterious disappearance, which she did not succeed either. Her strenuous research was a very unusual act for a woman of the time. She wrote a book about it. Ina v. Grumbkow also had a memorial erected in honor of the missing, which is located on the west side of the lake. The approximately 4 m high stone pyramid from 1908 was rediscovered on the large crater lake by Icelandic expert and author Frank Schroeder in 1994.

Fundamental research results on Askja go back to the companion and later husband Ina von Grumbkows named Hans Reck. The fate of the two German Icelandic explorers von Knebel and Rudloff has not yet been fully clarified.

More German scientists

In the 1930s, other German researchers also concentrated on exploring and mapping the Sveinagraben. However, they also dealt with the Askja central volcano and the Herðubreið.

Drekagil, Hvannalindir and Kverkfjöll

5 km east of Öskjuvatn is ⊙ Drekagil , the Dragon Gorge. This is noticeable due to its striking rock formations and ends after about 300 meters at a waterfall.

The oasis ⊙ Hvannalindir , which has been a nature reserve since 1973, is 25 km southeast of the Askja . At the end of the 18th century, the outlaw Fjalla-Eyvindur is said to have stayed here with his wife for a few years.

About 40 km south of the Askja are the volcanic mountains ⊙ Kverkfjöll with a glacier and an active geothermal area.

Trivia

See also

literature

  • Thor Thordarson, Armann Hoskuldsson: Iceland (Classic Geology in Europe 3). Terra Publishing, Harpenden 2007, ISBN 1-903544-06-8
  • Lutz Mohr : Iceland - fascination and mystery. Tragedy of German researchers on the Icelandic crater lake. For Iceland's national holiday on June 17th. In: Greifswalder Blitz on Wednesday. Volume 2, No. 48 of June 14, 1995, pp. 1f
  • Frank Schroeder: The Eisumschlungene. Searching for traces in Iceland. Eichstätt: LundiPress Verlag 1995, ISBN 3-980 164 8-3-7

Web links

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

Scientific contributions

Other

Individual evidence

  1. ^ HU Schmid: Dictionary Icelandic-German. Buske, Hamburg 2001, p. 9.
  2. ↑ a b Askja in the Global Volcanism Program of the Smithsonian Institution (English)
  3. ↑ a b c Askja in the Global Volcanism Program of the Smithsonian Institution (English), see: "Eruptive History".
  4. ^ A b c Thor Thordarson, Armann Hoskuldsson: Iceland. Classic Geology in Europe 3. Terra, Harpenden 2002, p. 172.
  5. ↑ Ísland Vegaatlas. Ferðakort, Reykjavík 2006, p. 20.
  6. ↑ Ásta Rút Hjartadóttir: The fissure swarm of the Askja central volcano. Univ. of Iceland, MS thesis, 2008 ( Memento from July 27, 2008) (PDF; 4.9 MB), p. 3
  7. ↑ Thor Thordarsson, ibid., P. 173.
  8. ↑ Thor Thordarson, Armann Hoskuldsson: Iceland. Classic Geology in Europe 3. Terra, Harpenden 2002, p. 172 f.
  9. ↑ a b c d Thor Thordarson, Armann Hoskuldsson: Iceland. Classic Geology in Europe 3. Terra, Harpenden 2002, p. 175.
  10. ↑ a b c d Th. Einarsson u. a. (Ed.): Íslandshandbókin. Náttúra, saga og sérkenni. 2. bindi. 1989, p. 913 f.
  11. ↑ Thor Thordarson, Armann Hoskuldsson: Iceland. Classic Geology in Europe 3. Terra, Harpenden 2002, p. 175 f.
  12. ^ A b c Thor Thordarson, Armann Hoskuldsson: Iceland. Classic Geology in Europe 3. Terra, Harpenden 2002, p. 176.
  13. ↑ a b H. Rymer: New mass increase beneath Askja volcano, Iceland - a precursor to renewed activity? In: Terra Nova. 22, 2010, pp. 309-313. doi : 10.1111 / j.1365-3121.2010.00948.x (abstract, English); Accessed July 24, 2011
  14. ↑ cf. z. B. Tremor Measurements at Askja, Icelandic Met Office, July 24, 2011 ; Accessed July 24, 2011
  15. ↑ http://icelandreview.com/news/2014/07/23/askja-closed-due-huge-landslide (accessed on August 19, 2014)
  16. ↑ Erin Mahoney: NASA - Past and Present: Field Testing For The Moon. In: NASA Official Website. NASA Headquarters, July 28, 2009, accessed July 26, 2012 .
  17. ^ A b Glen E. Swanson: Apollo Geology Field Exercises. (PDF; 24 kB) NASA Headquarters, pp. 4, 6 , archived from the original on October 21, 2011 ; accessed on July 26, 2012 (English).
  18. ↑ Katharina Hauptmann: Moon-Land (KH) - Iceland Review Online. In: Iceland Review Online. icelandreview.com (Heimur hf), August 24, 2011, accessed July 26, 2012 .
  19. ↑ a b cf. also: Th. Einarsson u. a. (Ed.): Íslandshandbókin. Náttúra, saga og sérkenni. 2. bindi. 1989, p. 914.
  20. ^ Ina von Grumbkow: Ísafold. Travel pictures from Iceland
  21. ↑ Ásta Rút Hjartadóttir: The fissure swarm of the Askja central volcano. Univ. of Iceland, MS thesis, 2008 ( Memento from July 27, 2008) (PDF; 4.9 MB), p. 37
  22. ↑ Ásta Rút Hjartadóttir: The fissure swarm of the Askja central volcano. Univ. of Iceland, MS thesis, 2008 ( Memento from July 27, 2008) (PDF; 4.9 MB), p. 4 f.
  23. ↑ T. Einarsson, H. Magnússon (Eds.): Íslandshandbókin. Náttúra, saga og sérkenni. 2. bindi. 1989, p. 920 f.