Bárðarbunga

From Wikipedia, the free encyclopedia
Jump to: navigation, search
Bárðarbunga
Bárðarbunga is located in Iceland
Bárðarbunga
Bárðarbunga
Map of Iceland showing the location of Bárðarbunga.
Elevation 2,009 m (6,591 ft)
Prominence 550 m (1,800 ft)
Location
Location Vatnajökull, Iceland
Coordinates 64°38′27.6″N 17°31′40.8″W / 64.641000°N 17.528000°W / 64.641000; -17.528000Coordinates: 64°38′27.6″N 17°31′40.8″W / 64.641000°N 17.528000°W / 64.641000; -17.528000
Geology
Type Subglacial volcano/Icelandic stratovolcano
Age of rock approx. over 100 years
Last eruption June to October 1910

Bárðarbunga ([ˈpaurðarpuŋka] ( )),[1] Bardarbunga (Anglophone spelling), is a stratovolcano located under Vatnajökull, Iceland's most extensive glacier. The second highest mountain in Iceland, 2,009 metres (6,591 ft) above sea level, Bárðarbunga is also part of a volcanic system that is approximately 200 kilometres (120 mi) long and 25 kilometres (16 mi) wide. Bárðarbunga volcano is currently showing increasing signs of significant activity including an earthquake swarm, an orange aviation warning or no-fly zone is currently in force.

Description[edit]

Bárðarbunga is a subglacial stratovolcano[2] located under the ice cap of Vatnajökull glacier within the Vatnajökull National Park in Iceland. It rises to 2,009 metres (6,591 ft) above sea level, making it the second highest mountain in Iceland, about 101 metres (331 ft) lower than Hvannadalshnjúkur. The caldera is about 70 square kilometres, up to 10 kilometres (6 mi) wide and about 700 metres (2,300 ft) deep.[2] The surrounding edges rise up to 1,850 metres but the base is on average close to 1,100 metres. The volcano is covered in ice, hiding the glacier-filled crater.

Bárðarbunga was a little-known volcano in Iceland due to its remote location and infrequent eruptions, but recent studies have shown that many tephra layers originally thought to be from other volcanoes were ejected from Bárðarbunga.

Sustained seismic activity has occurred in Bárðarbunga for some years without an eruption, thus the volcano is still active. There has been frequent volcanic activity outside the glacier to the south-west in the highlands between Vatnajökull and Mýrdalsjökull, also to the north-east toward Dyngjufjöll.

Over the last seven years seismic activity has been gradually increasing in Bárðarbunga and the fissure swarm to the North of the volcano. This activity reduced after the Grímsvötn eruption in May 2011 but has now returned to a similar level as before the eruption.

Etymology[edit]

Bárðarbunga is named after an early Icelandic settler named Gnúpa-Bárður, and literally translates as "Bárður's bulge" or "Bárður's bump" since "Bárðar" is the genitive case (possessive case) of "Bárður". [3]

Eruptions and notable activity[edit]

Throughout history there have been large eruptions every 250–600 years. In 1477, the largest eruption from Bárðarbunga had a volcanic explosivity index (VEI) of 6; there is evidence of many smaller eruptions during the past 10,000 years.[2]

6600 BC[edit]

Þjórsá Lava, the largest holocene lava flow on earth,[2] originated from Bárðarbunga about 8,500 years ago, with a total volume of 21[2] to 30 cubic kilometres and covering approximately 950 square kilometres.[4]

870[edit]

Many large eruptions have occurred south-west of the glacier, the first since human settlement of Iceland was the Vatnaöldur eruption about 870 which had a volcanic explosivity index (VEI) of 4.[2]

1477[edit]

The Veiðivötn eruption in 1477 is the largest known Icelandic eruption, with a VEI of 6.[2]

1701–1864[edit]

Studies of tephra layers have shown that a number of eruptions have occurred beneath the glacier, probably in the north-east of the crater or in Bárðarbunga. There have also been smaller eruptions in an ice-free area of Dyngjuháls to the north-east. Eruptions appear to follow a cycle: there were several eruptions in the glacier between 1701 and 1740 and since 1780. There hasn't been an eruption in the glacier or the system since 1862–64.[clarification needed].

1996[edit]

The Gjálp fissure vent eruption in 1996 revealed that an interaction may exist between Bárðarbunga and Grímsvötn. A strong earthquake in Bárðarbunga, about 5 on the Richter scale, is believed to have started the eruption in Gjálp.

2010[edit]

On 26 September 2010 an earthquake swarm was recorded with over 30 earthquakes measuring up to 3.7MW on the moment magnitude scale.[citation needed]

2014[edit]

In August 2014 a swarm of around 1,600 earthquakes in 48-hours, with magnitudes up to 4.5MW, [5][6] was followed on 23 August by the USGS Aviation Color Codes being raised from orange to red, indicating an eruption in progress.[7] The following day, the aviation risk was lowered from red to orange and the statement that there was an eruption in progress was retracted.[8]

August 2014 seismic activity[edit]

Overview[edit]

Seismic activity surrounding the Bárðarbunga volcano has been gradually increasing since 2007 with a brief respite during the eruption at Grímsvötn in 2011. Activity has now reached a level similar to that just before the Grímsvötn eruption. In May 2014 there was a small earthquake swarm of about 200 events. GPS data has recorded a displacement of 14cm in this region since the beginning of the latest bout of activity compared to a figure of 2cm over the rest of Iceland. This displacement is attributed to the separation of two continental plates over a mantle plume which means magma flows to fill fissures created in the Earth's crust creating a volcanic "hot spot". Two earthquake swarms have been detected with continuous activity since the beginning of the event, one at Bárðarbunga caldera which is attributed to subsidence as the magma chamber empties, and the other at the head of a dyke which extends about 5-8km below the surface and about 40km to the North East which continues to move away from the volcano and has now cleared the edge of the glacier. Following a meeting on 25 August scientists at the Icelandic Met Office and the University of Iceland have outlined four possible scenarios:

  • A reduction in seismic activity following a halt in the migration of magma.
  • An eruption of mostly lava reaching the surface probably near the northern tip of the dyke.
  • An eruption somewhere along the dyke beneath the glacier which could produce an explosion, eject ash, and create a glacial outburst flood.
  • A less likely but still possible scenario is an eruption within the caldera of the volcano itself.

16 August[edit]

A swarm of earthquakes of average magnitude 1.5 up to M3 began at 3am on 16 August 2014 generating 1600 earthquakes, there are "Very strong indications of ongoing magma movement, in connection with dyke intrusion" according to the Icelandic Metrological Office.[7] The activity is in fact two swarms one located East of Bárðarbunga caldera and one at the edge of Dyngjujökull glacier just E of Kistufell. The Aviation Color Code[9] was set to yellow.

18 August[edit]

By 18 August the swarm numbered about 2600 earthquakes, some larger than magnitude 3, the largest was magnitude 4.5. The aviation code was changed to orange. The majority of events have been recorded at a depth of 5–10 km.

23 August[edit]

On 23 August an intense low-frequency signal was detected which led scientists to believe that a small eruption was in progress under the Dyngjujökull glacier, as a result of this the aviation colour code was elevated to red signifying that an eruption is either imminent or in progress and meaning a no fly zone for planes to the South East of Iceland.

24 August[edit]

Three M5 earthquakes, the strongest in Iceland since 1996, were recorded on 24 August, the first at 00:09, but there were no signs visible on the surface. "Probably, earthquakes near the Bárðarbunga caldera are a consequence of adjustment to changes in pressure because of the flow of magma from under the caldera into the dyke which stretches to Dyngjujökull, more than 25 km away."[10] Following the scientists' meeting at 11:50, the aviation code was reduced to orange. It was stated that 700 earthquakes of larger magnitudes than previously recorded had been observed since midnight; the dyke stretching to the North was estimated at 30 km in length; activity showed no signs of abating and an imminent eruption was considered possible; the intense low frequency signal detected on 23 August was not caused by a sub-glacial eruption.

25 August[edit]

By 19:00 there had been about 1200 earthquakes at depths of 5-12km, mostly around the northern tip of the intrusion northeast of Bárðarbunga which had migrated further to 6-7 km north of Dyngjujökull. More than twenty were of intensity M3–M4, and one at 16:19, within the caldera, was 5.1M. There was no sign of volcanic harmonic tremor.

26 August[edit]

Intense seismic activity continued, with no signs of reduction and approximately 900 events recorded by 6pm. The largest earthquake since the 2014 activity began occurred at 1:26 am, magnitude 5.7 on the North-West rim of the caldera at a depth of 6km. The dyke continued to extend to the North, reaching forty kilometres from the caldera and 5 km past the edge of the glacier. Activity was concentrated at the tip which now extends across an area of 10 km. GPS modelling shows that fifty million cubic metres of magma were added to the dyke in the previous 24 hours forming a total of 350 million cubic metres.

27th August[edit]

By 18:42 there had been two earthquakes in the Caldera above M5 and about 1300 events in the range of magnitude 2-3 around the tip of the dyke which has propagated a further 1km to the North and now reaching some 13km past the edge of the glacier, about 20 million cubic metres of magma was added over 24 hours. The dyke intrusion is now causing stress changes over a large area to the North of the dyke's extent. A magnitude 4.5 event was recorded just East of the Askja caldera which has been showing signs of increased geothermal activity since April 2012. Scientists on a surveillance flight reported at 20:50 a 6-4km row of 10-15m deep cauldrons to the South of the Bárðarbunga caldera that are possibly a result of melting or a sub glacial eruption although they don't know when, no heightened tremor level or volcanic harmonic tremor has currently been observed.

Icelandic Met Office[edit]

The Icelandic Met Office's seismicity Web page is updated several times a day.

Aircraft emergency landing[edit]

On 14 September 1950 a Douglas C-54 Skymaster aircraft belonging to the Icelandic airline Loftleiðir made an emergency landing on the Vatnajökull glacier at Bárðarbunga during a cargo flight from Luxembourg to Reykjavík.[11] There were no fatalities, but damaged radio equipment left them unable communicate their location. After two days the crew started the emergency SOS signal beacon in the rubber life-raft and a Loftleiðir Catalina aircraft spotted them. The C-54's cargo included the body of a deceased USAF colonel, prompting American assistance. A USAF C-47 equipped with skis landed on the glacier but was unable to take off again, so it had to be abandoned. After six days both crews were rescued by a ski-patrol from Akureyri. Later Loftleiðir bought the stranded C-47 from the USAF for $700.[12] In April 1951 it was dug out of the snow and towed down the mountain by two bulldozers, where it was started and flown to Reykjavik.[13][14][15]

See also[edit]

References[edit]

  1. ^ mbl.is (2011-05-22). "How To Pronounce "Bárðarbunga"". YouTube.com. Retrieved 2014-08-20. 
  2. ^ a b c d e f g "Bárdarbunga". Global Volcanism Program, Smithsonian Institution. http://www.volcano.si.edu/world/volcano.cfm?vnum=1703-03%3D. Retrieved 2009-06-18.
  3. ^ Stofnun Árna Magnússonar - í íslenskum fraedum. Bárðarbunga
  4. ^ Árni Hjartarson 1988: „Þjórsárhraunið mikla - stærsta nútímahraun jarðar“. Náttúrufræðingurinn 58: 1-16.
  5. ^ Gunn­ar Dof­ri Ólafs­son, 1.600 eart­hqua­kes in 48 hours. mbl.is. 2014-08-19.
  6. ^ "Activity in Bárðarbunga volcano- News- About IMO- Icelandic Meteorological Office". En.vedur.is. 2014-08-16. Retrieved 2014-08-20. 
  7. ^ a b Icelandic Met Office (2014-08-23). "Bárðarbunga - updated information". Icelandic Met Office. Retrieved 2014-08-23. 
  8. ^ BBC (2014-08-24). "Iceland volcano: Aviation risk level from Bardarbunga lowered". BBC. Retrieved 2014-08-24. 
  9. ^ Icelandic Met Office (2014-08-24). "Aviation colour code map". Icelandic Met Office. Retrieved 2014-08-24. 
  10. ^ Icelandic Met Office (2014-08-24). "Bárðarbunga - updated information". Icelandic Met Office. Retrieved 2014-08-24. 
  11. ^ http://aviation-safety.net/database/record.php?id=19500914-0
  12. ^ [1]
  13. ^ 1950 accident at the Aviation Safety Network
  14. ^ Timeline of the search for the Geysir at gopfrettir.net (in Icelandic)
  15. ^ Timarit - Iceland. Lögberg-Heimskringla.

External links[edit]