Kverkfjöll
Kverkfjöll is a potentially active central volcano, fissure swarm, and associated mountain range situated on the northern border of the glacier Vatnajökull in Iceland.
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. 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.
Geography
The maximum elevation of the central volcano at the peak of Skarphéðinstindur is. 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. 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 and to the south of the central volcano it is possible that a subglacial fissure swarm extends for.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. The Holocene active volcanic fissures are mostly confined to the nor-north-east orientated Kverkfjöll fissure swarm, rather than the north-east orientated Kverkárnes fissure swarm. 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, which is a stratovolcano. There is a geothermal field just beyond the western rim of the northernmost caldera. This has created ice–dammed lakes called Gengissig and Galtarlón. 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. The oldest identified rocks are 780,000 years old.The tectonic context is that the Kverkfjöll volcanic system is part of the divergent plate boundary northern volcanic zone of Iceland 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 depth under Kverkfjöll, with lower crustal magma intrusion to pockets that are about deep, and its hydrothermal system being driven by a magma intrusion pocket about deep with the hydrothermal water reservoir being at about deep.