Bárðarbunga

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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 August to September 2014 (ongoing)

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.

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 80 square kilometres, up to 10 km 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 to a depth of 850m, hiding the glacier-filled crater. The associated volcanic system and fissure swarm is about 190km long and 25km wide.[3]

Bárðarbunga was a little-known volcano in Iceland due to its remote location and infrequent eruptions approximately once every 50 years, 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 only recently leading to an eruption, the previous eruption was in 1910. 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". [4]

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.[5]

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.

1910 eruption[edit]

1910 was the last known eruption of Bárðarbunga before the 2014 eruptions.[6]

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, [7][8] was followed on 23 August by the USGS Aviation Color Codes being raised from orange to red, indicating an eruption in progress.[9] The following day, the aviation risk was lowered from red to orange and the statement that there was an eruption in progress was retracted.[10] However, later aerial observations of glacial depressions southeast of the volcano suggested that the now-retracted report of an eruption had been correct and that a short eruption did occur under the ice, but the lack of further melting indicated that this eruption had now ceased. Then, a new fissure eruption breached the surface between Bárðarbunga and Askja, in the Holuhraun lava field, in the early hours of 29 August.[11] This was followed by a second fissure eruption in the Holuhraun area, along the same volcanic fissure, which started shortly after 4am on 31 August.[12]

August and September 2014 seismic activity and Holuhraun eruption[edit]

Eruption at Holuhraun, September 4 2014
Lava at Holuhraun, September 4 2014

Overview[edit]

Seismic activity surrounding the Bárðarbunga volcano gradually increased from 2007 to 2014 with a brief respite during the eruption at Grímsvötn in 2011.[13] By the summer of 2014 activity 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 recorded a displacement of 14cm in this region since the beginning of this 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. Scientists at the Icelandic Met Office and the University of Iceland outlined four possible scenarios:[13]

  • 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.
  • An eruption within the caldera of the volcano itself.[13]

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.[13] The activity is in fact two swarms one located East of Bárðarbunga caldera and one at the edge of Dyngjujökull glacier just east of Kistufell. The Aviation Color Code[14] 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 5–10km.[13]

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.[13]

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." 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.[13]

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.[13]

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.[13]

27 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.[13]

28 August[edit]

Similar seismic activity to previous days with 1100 earthquakes detected from midnight to 18:14, three magnitude 4 earthquakes in the caldera and one M5 at 08:13. The dyke had expanded 1-1.5km to the north and is now interacting with the fissure system of Askja volcano according to GPS measurements. A few earthquakes were detected near Askja, the biggest one of M2.7. The water level in Grímsvötn Lake rose by 5-10m with melt water from the cauldrons south of the caldera.[13]

29 August[edit]

At 00:02 lava erupted approx 5 km north of the margin of the Dyngjujökull glacier confirmed by visual and seismic tremor observations.[15] The fissure eruption breached the surface between Bárðarbunga and Askja, close to the northernmost point of the earthquake swarm, in the Holuhraun lava field.[11] The active fissure was about 600 metres long producing a lava flow which peaked between 00:40 and 01:00 and is thought to have ceased by 4am. Seismicity reduced during the eruption but then returned to the same levels as before.[16] At 10am the aviation alert for Bárðarbunga region was downgraded to orange signifying no hazard from an ash cloud, Askja volcano aviation alert code remains at yellow status.[13]

30 August[edit]

The dyke has stopped migrating northwards although seismic activity continues at similar levels to previous days with 1100 earthquakes detected from midnight to 18:00 including a magnitude 5.4 in the caldera. A few small events around Askja volcano, no further signs of eruption.[13]

31 August[edit]

At 04:00am another fissure eruption began in the Holuhraun lava field, it is estimated about 1.5 km along the same fissure as the previous eruption. By 7am the lava flow was 1km wide and 3km long towards the north-east and several metres thick, the flow was approx 1000 cubic metres per second. Gas emissions were rising a few hundred metres above the eruption but no ash cloud was detected. At about 1pm a magnitude 5.1 earthquake occurred in the caldera at Bárðarbunga. GPS measurements show continuing changes to the north of the eruption, seismic activity is reduced but otherwise similar to previous days.[13]

1 September[edit]

The fissure in Holuhraun erupts continuously along its 600-800m central section. The lava stretches over 4 square kilometres with an estimated 20-30 million cubic metres, 5-10 million cubic metres in the last 19 hours, the average flow is about 100 cubic metres per second. A white plume rises about the eruption to 15000 feet reaching 60km NNE, there does not appear to be any ash but high levels of sulphur dioxide have been recorded. Seismic activity around the area is similar to previous days but is reduced as a result of the release of pressure from the eruption.[13]

2–3 September[edit]

Reduced seismic activity along similar lines as previous days was reported as the ongoing eruption continued to ease pressure in the fissure below. The lava flow area was estimated at 7.2 square kilometres. On 3 September, a new development was noted regarding a 0.5–1km wide depression forming around the eruption area and also extending possibly below the glacier for 2km to the south. A magnitude 5.5 earthquake occurred in the caldera at 03:09. A low frequency continuous tremor signal of variable intensity has been detected but scientists have not been able to attribute it to any signs of a sub-glacial eruption.[13]

4th-5th September[edit]

Eruptions continue with the lava covering 12 square kilometres. Seismic activity continues along similar lines with activity near the tip of the dyke and larger earthquakes in the caldera. At 7am on 5th September two new smaller eruptions appeared in a graben to the South of the on-going eruption about 2km from Dyngjujökull glacier. The cauldron at Dyngjujökull appears to have grown. Low frequency tremors continue to be detected and substantial amounts of Sulphur dioxide are emitted from the eruptions.[13]

6th September[edit]

Two eruptive fissures continue to be active at Holuhraun as per previous days. Earthquake activity continues to decrease but M5 events still occur in the caldera on a daily basis. Surveillance flight radar has shown 15 metres of subsidence of the glacier surface within the caldera, a volume change of 0.25 square kilometres. This is the largest observed subsidence in Iceland since records began in the middle of the last century. A shallow wide depression was also observed at the Dyngjujökull glacier 10 km from the ice margin, another depression 6 km from the margin has deepened to 35 metres. These are thought to be probably caused by small and short sub-glacial eruptions.[13]

7th September[edit]

Earthquake activity continues at three locations, Bárðarbunga caldera had an M5.4 at 07:08 one of the largest so far recorded during this spate of activity, also at the Northern part of the dyke and at Herðubreiðatögl according to the geoscientist on duty reporting at 19:00. Eruptions now produce 100-200 m3/s of lava which has covered about 16 km2. Lava has now reached the western part of the Jökulsá á Fjöllum river and steaming occurs.[13]

8th September[edit]

Following the measurement on Sept. 6th, the glacier subsided another 2.5 to 3 meters since. [17] The University of Iceland said that "The events in Bardarbunga can only be described as a slow caldera collapse". [18]

Further the geoscientist on duty reported at 19:20 that four earthquake events greater than 4 occurred around the caldera rim, one of which at 5.0. Another earthquake swarm took place further north of Herðubreið. [13]

9th-10th September[edit]

Earthquakes continue to be recorded at Bárðarbunga caldera with an M5.5 at 05:28 on 10-09-2014, also in the northern part of the dyke intrusion and at Herðubreiðatögl. Lava is flowing into the river bed at Jökulsá á Fjöllum but there is no explosive reaction, only steaming. There are concerns about air quality due to Sulphur dioxide emissions both at the eruption sites and generally in urban areas in East Iceland. Most of the magma flowing into the dyke is being erupted without forcing any further crustal deformations, according to GPS measurements. Forecast scenarios now include references to possible further subsidence in the caldera prompting eruptions beneath the Dyngjujökull glacier.[13]

11th-18th September[edit]

The eruption in Holuhraun continues at a similar rate, reported earthquakes have continued at the intrusion which have declined over this last week but increased in the last 24 hours, the Caldera continues to subside with regular m5 earthquakes each day. Air quality is affecting the region depending on wind direction. In the last two days GPS monitoring has detected unusual crustal movements which may indicate a change in the movement of magma under the volcano. In the month from 16th August when the earthquakes began at Bardarbunga 25,000 earthquakes have been automatically recorded, this is compared to 10,000 - 15,000 earthquakes recorded throughout Iceland in an average year.[13]

21st September[edit]

Subsidence in the caldera measured by the newly mounted GPS station shows approximately 40cm per day and appears to coincide with earthquake activity.[19] Lava flow and gas emissions continue at the same strength at the eruption site in Holuhraun. The lava field now extends to 37 squared kilometres.[13]

Icelandic Met Office[edit]

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

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.[20] There were no fatalities, but damaged radio equipment left them unable to 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.[21] 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.[22][23][24]

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. ^ http://en.vedur.is/about-imo/news/nr/2968
  4. ^ Stofnun Árna Magnússonar - í íslenskum fraedum. Bárðarbunga
  5. ^ Árni Hjartarson 1988: „Þjórsárhraunið mikla - stærsta nútímahraun jarðar“. Náttúrufræðingurinn 58: 1-16.
  6. ^ http://en.vedur.is/media/jar/Bardarbunga_kafli20140825.pdf
  7. ^ Gunn­ar Dof­ri Ólafs­son, 1.600 eart­hqua­kes in 48 hours. mbl.is. 2014-08-19.
  8. ^ "Activity in Bárðarbunga volcano- News- About IMO- Icelandic Meteorological Office". En.vedur.is. 2014-08-16. Retrieved 2014-08-20. 
  9. ^ Icelandic Met Office (2014-08-23). "Bárðarbunga - updated information". Icelandic Met Office. Retrieved 2014-08-23. 
  10. ^ BBC (2014-08-24). "Iceland volcano: Aviation risk level from Bardarbunga lowered". BBC. Retrieved 2014-08-24. 
  11. ^ a b "Eruption Started Between Barðarbunga and Askja in Iceland". Wired.com. 2014-08-29. Retrieved 2014-08-29. 
  12. ^ "Scientists: Bigger Eruption, Moves North. 500 Earthquakes". Icelandreview.com. 2014-08-31. Retrieved 2014-08-31. 
  13. ^ a b c d e f g h i j k l m n o p q r s t u v w http://en.vedur.is/earthquakes-and-volcanism/articles/nr/2947
  14. ^ Icelandic Met Office (2014-08-24). "Aviation colour code map". Icelandic Met Office. Retrieved 2014-08-24. 
  15. ^ #D Bulge
  16. ^ http://www.ruv.is/frett/eldgos-hafid-i-holuhrauni
  17. ^ [1] http://www.ruv.is/frett/continuing-subsidence-in-bardarbunga
  18. ^ [2] http://jardvis.hi.is/nyjar_maelingar_siginu_i_bardarbungu
  19. ^ http://en.vedur.is/earthquakes-and-volcanism/gps-measurements/bardarbunga/caldera/
  20. ^ http://aviation-safety.net/database/record.php?id=19500914-0
  21. ^ [3]
  22. ^ 1950 accident at the Aviation Safety Network
  23. ^ Timeline of the search for the Geysir at gopfrettir.net (in Icelandic)
  24. ^ Timarit - Iceland. Lögberg-Heimskringla.

External links[edit]