Eldgjá

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Ófærufoss 1975
Eldgjá

The Eldgjá ( Icelandic fire gorge) is an approx. 8 km long gorge, the central part of the 75 km long volcanic fissure of the same name, which belongs to the volcanic system of the central volcano Katla in Iceland .

Location and discovery

The Eldgjá Gorge is located in the south of the highlands between Landmannalaugar and Kirkjubæjarklaustur in the municipality of Skaftárhreppur and is up to 150 m deep and up to 600 m wide. Þorvaldur Thoroddsen discovered the gorge on July 22, 1893.

Breakout series 939/40

The Eldgjá was formed during an eruption in the middle of the 10th century, which must have had considerable proportions, because the amount of lava that flowed out is estimated at over 18 cubic kilometers and the tephra thrown into the air at 1.4 cubic kilometers. In 1995 the eruption could be dated to 938 ± 4 based on analysis of samples from the Greenland Ice Sheet as part of the GISP2 project and dendrochronology . With the help of the entry CS 939 in the Chronicon Scotorum , an Irish text with annals that presumably originated in Clonmacnoise , the event could be dated more precisely to the year 939 as part of a 1997 analysis. The entry reports a blood-red sun from early morning until noon the following day. This observation is attributed to the at least 14 km high eruption column of the Eldgjá, ​​which reached the stratosphere . In connection with the previous knowledge, the time of the eruption could be specified to spring 939. The outbreak has been linked to reports of a very cold winter in 939/940, accompanied by poor harvests and famine. In addition, significant temperature and precipitation fluctuations could be detected in the entire northern hemisphere in the following years and a connection with the Christianization of Iceland is seen.

Probable sequence of the breakout series

The series of eruptions began with a massive explosive eruption at the southwest end of the fissure that lies under Mýrdalsjökull . This triggered glacier runs in an easterly direction over the Mýrdalssandur and also over the Mælifellssandur in a northerly direction. At the same time there was an eruption in the Katla caldera. This was followed by effusive eruptions in the ice-free part of the crevice that adjoins Mýrdalsjökull to the north.

The middle part of the fissure, the actual Eldgjá gorge, was created in the next phase of the eruption. Finally, there were also eruptions in the northeast on the edge of Vatnajökull . The respective outbreak series began with an explosive phase and ended with an effusive phase.

Overall, the outbreaks lasted about 3–4 years or, according to more recent studies, from spring 939 to autumn 940.

Traces of the eruption

The walls of the gorge are made of palagonite , but are covered with cinder. Some traces suggest the presence of lava columns. The cinder craters on the floor of the Eldgjá are likely to have been active at the time.

Environmental impact

In terms of environmental impact, Eldgjá was one of the largest eruptions in historical times, far surpassing that of the Lakikrater , but also that of Tambora from 1815. It injected 219 million tons of sulfur dioxide into the atmosphere, where it reacted with water and oxygen to become 450 million tons of sulfuric acid . The aerosols must have covered much of the Northern Hemisphere .

In 940, Central Europe, Scandinavia, Central Asia and parts of Canada experienced a significantly cooler summer than usual. The Chronicon Scotorum mention blood-red sunlight for the year 939. The Res gestae Saxonicae and other historical sources from Ireland and China point to severe winters in 939/40 and 940/41 respectively. In Egypt the level of the Nile was particularly low, in Inner Mongolia snow fell in the summer of 939.

Influence on the population

The impact on the population must have been devastating. Interestingly, however, none of the known Icelandic sources on the Middle Ages directly mentions the eruption, neither the Landquisition Book ( Landnámabók ) nor the Icelandic Book ( Íslendingabók ), the history of Iceland by the scholar Ari fróði . Various theories exist about this striking silence about such a significant event. Among other things, one suspects that they would not have wanted to deter other settlers from Iceland.

It is possible, however, that the eruption and its consequences that the early settlers experienced in Iceland are reflected in some stanzas of Völuspá , the first song of the gods in the Codex Regius (Edda) . For the years 939 to 941 are made from parts of Europe, China and Persia from crop failures and famines handed.

Ófærufoss waterfall

A waterfall, the Ófærufoss , is located in the gorge. It used to be crossed over a natural bridge, which however collapsed as a result of the snowmelt in the winter of 1992/1993.

Transport links

Eldgjá can be reached from the south via Skaftártunguvegur 208 and the highland road Fjallabaksleið nyrðri SxF208 from the ring road . Several rivers have to be crossed. The highland road continues via Landmannalaugar to the southern end of the Sprengisandur highland slope . To the northeast of the Eldgjá are the Laki craters .

See also

literature

  • Werner Schutzbach: Katla, the story of an Icelandic volcano. Reykjavík 2005

Web links

Scientific contributions

Photos

Other

Individual evidence

  1. ↑ Thor Thordarsson, Armann Hoskuldsson: Iceland.Classic Geology in Europe 3. Harpenden 2002, p. 109.
  2. ↑ Martin Scharzbach, Geologenfahrt auf Iceland, 3rd edition 1971, p. 68
  3. ↑ a b Thor Thordarsson, ibid., P. 110
  4. ↑ Gregory A. Zielinski, Mark S. Germani, Gudrún Larsen, Michael GL Baillie, Sallie Whitlow, Mark S. Twickler and Kendrick Taylor: Evidence of the Eldgjá (Iceland) eruption in the GISP2 Greenland ice core: relationship to eruption processes and climatic conditions in the tenth century . In: The Holocene . Volume 5, No. 2, 1995, pp. 129-140.
  5. ^ Daniel McCarthy and Aidan Breen: Astronomical observations in the Irish annals and their motivation . In: Peritia . Volume 11, 1967, pp. 1-47 (here: p. 17 with the entry for the year 939).
  6. ↑ Michael McCormick, Paul Edward Dutton and Paul A. Mayewski: Volcanoes and the Climate Forcing of Carolingian Europe, AD 750-950 . In: Speculum . Volume 82, No. 4, October 2007, pp. 865-895 (here: Event 8 pp. 888-889), JSTOR 20466080 . To estimate the height of the eruption column, see Gregory A. Zielinski, Mark S. Germani, Gudrún Larsen, Michael GL Baillie, Sallie Whitlow, Mark S. Twickler and Kendrick Taylor: Evidence of the Eldgjá (Iceland) eruption in the GISP2 Greenland ice core: relationship to eruption processes and climatic conditions in the tenth century . In: The Holocene . Volume 5, No. 2, 1995, pp. 129-140 (here: p. 131).
  7. ↑ a b c d e f Clive Oppenheimer, Andy Orchard, Markus Stoffel, Timothy P. Newfield, Sébastien Guillet, Christophe Corona, Michael Sigl, Nicola Di Cosmo, Ulf Büntgen: The Eldgjá eruption: timing, long-range impacts and influence on the Christianization of Iceland , in: Climatic Change (2018) 1–18, doi: 10.1007 / s10584-018-2171-9 .
  8. ↑ Schutzbach, p. 34ff.
  9. ↑ Thor Thordarsson, ibid., Pp. 109–110
  10. ↑ Also: Daniel Lingenhöhl: Why Iceland became Christian. In: Spektrum.de. March 19, 2018. Retrieved April 14, 2018 .

Coordinates: 63 ° 57 ′ 47 "  N , 18 ° 37 ′ 8"  W.