Kverkfjöll

File:Vatnajökull - Kverkfjöll - Glacier cave.jpg

Glacier cave near Kverkfjöll.

File:Kverkjollwarning.JPG

Warning text about the caves.

Kverkfjöll () is a potentially active central volcano, fissure swarm, and associated mountain range situated on the northern border of the glacier Vatnajökull in Iceland.Template:Sfn

It is located in Vatnajökull National Park and at the glacier edge are ice caves and some geothermal features.

The main volume of the Jökulsá á Fjöllum river flows from the Kverkfjöll area. The Volga River directly drains the Kverkjökull glacier into the Jökulsá á Fjöllum.Template:Sfn These river systems have had significant jökulhlaups during the Holocene that are related to the three active volcanic systems of Bárðarbunga, Grímsvötn and Kverkfjöll but assignment has been difficult to individual volcanic systems.Template:Sfn

Geography

The maximum elevation of the central volcano at the peak of Skarphéðinstindur is Template:Cvt.Template:SfnTemplate:Efn The central volcano is mainly situated under Kverkjökull, an outlet glacier of Vatnajökull. The Kverkjökull icecap to the north-west of Skarphéðinstindur, has a maximum elevation of Template:Cvt. To the west of Kverkjökull is the Dyngjujökull outlet glacier and to its east is the Skarphéðinsjökull adjacent to the Brúarjökull outlet glaciers of Vatnajökull. To the north of the central volcano there is a fissure swarm striking N20-30°E for Template:Cvt and to the south of the central volcano it is possible that a subglacial fissure swarm extends for Template:Cvt.Template:Efn

The area north of Kverkfjöll has been altered by large floods originating from the northern part of Vatnajökull with the heights being tindars and hyaloclastite ridges orientated towards the nor-north-east.Template:Sfn The Holocene active volcanic fissures are mostly confined to the nor-north-east orientated Kverkfjöll fissure swarm (Kverkfjallarani western ridge), rather than the north-east orientated Kverkárnes fissure swarm (Kverkhnjúkar eastern ridge).Template:SfnTemplate:Sfn The 2014 to 2015 erupted Holuhraun lava field is approximately to the north-west of Kverkfjöll but is related to the adjacent Bárðarbunga volcanic system.

Geology

While the dominant magma is tholeiite basalt, samples of some rocks carried in the Kverkjökull glacier have been silicic and presumably originate from the central volcano,Template:Sfn which is a stratovolcano. There is a geothermal field just beyond the western rim of the northernmost caldera.Template:SfnTemplate:Sfn This has created ice–dammed lakes called Gengissig and Galtarlón.Template:SfnTemplate:Sfn They are drained by the thermal Volga river. Beyond the eastern rim of the northern caldera is another thermal river, the Hveragil that drains geothermal areas along the eastern northern caldera margin.Template:Sfn The oldest identified rocks are 780,000 years old.Template:Sfn

The tectonic context is that the Kverkfjöll volcanic system is part of the divergent plate boundary northern volcanic zone of IcelandTemplate:Sfn slightly to the north-east of the central volcanoes of the Grímsvötn and Bárdarbunga that are inferred to be closer to the Iceland mantle plume. The mantle is at about Template:Cvt depth under Kverkfjöll, with lower crustal magma intrusion to pockets that are about Template:Cvt deep, and its hydrothermal system being driven by a magma intrusion pocket about Template:Cvt deep with the hydrothermal water reservoir being at about Template:Cvt deep.Template:Sfn

Activity

Tephra studies have identified up to seventy eruptions in the last 6500 years,Template:Sfn but the volcano has been in relative repose in the last thousand years and had also been inactive for a period between 3000 and 4000 years ago.Template:Sfn Tholeiite basalt tephra from the volcano has been found to the west from eruptions dated 5850 ± 200 and 10630 ± 150 BP.Template:Sfn An earthquake swarm in 2007 to 2008 near Mount Upptyppingar,Template:Sfn which is Template:Cvt north-east of the Kverkfjöll central volcano was interpreted as a Template:Cvt dyke intrusion.Template:Sfn The most recent volcanic subaerial eruption occurred about 1300 years ago from the northern fissure swarm and produced a lava flow covering about Template:Cvt.Template:Sfn In 2013 a jökulhlaup occurred that emptied the water-filled Gengissig depression hydrothermal area, that is located just north-west to the northern caldera. Further than the flood, due to the release of water pressure, there were subsequent significant hydrothermal explosions in the lake bed.Template:Sfn Similar water floods or eruptions may have occurred since the mid-17th century. A hydrothermal eruption occurred in 1968, Template:Cvt to the west of the Gengissig depression, and jökulhlaups from the Gengissig depression occurred in 2002, 1997, 1993, 1987 and 1985.Template:Sfn Other low grade, possibly hydrothermal, eruptions assigned to the system, have occurred in 1968, 1959, 1929, 1729 (two), and 1655. At least two very large pre-history Holocene jökulhlaups that have had subsequent lava flows over them could have been generated by Kverkfjöll.Template:Sfn Before this a tephra layer called the Fugloyarbanki tephra from 27,000 years ago came from Kverkfjöll.Template:Sfn

See also

• Glaciers of Iceland
• Iceland plume
• List of lakes of Iceland
• Volcanism of Iceland
  • List of volcanic eruptions in Iceland
  • List of volcanoes in Iceland

External links

• Kverksfjöll Template:Webarchive in the Catalogue of Icelandic Volcanoes
• Kverkfjöll - picture gallery from islandsmyndir.is
• Photo
• ice cave
• Template:Cite gvp