Fremrinámur

Geology

There is a central volcano and a fissure swarm which is part of the Northern Volcanic Zone. The Fremrinámar volcanic system is about 130 km long, extending to the north sea coast, and up to 12 km wide. The last eruption was in 800 BC (± 300 years). However compositional analysis of at least one recent southern local lava shows similarities to lavas from the Bárðarbunga volcanic system and so eruption history local to the volcano requires further understanding. After the last ice age there have been two periods of local activity, with a large lava shield of more than 5 km3 volume in the early Holocene and at least three lava shields deposited between 5000 and 3000 years ago, including the 4 km3 Ketildyngja lava shield. The largest recent fissure eruption was 3200 years ago and produced the Búrfellshraun lava flow which is 75 km2 in area. Recent lavas have been tholeiite basalt but in the Pleistocene the central volcano erupted silicic lava and multiple tuyas and tindars were formed under the ice sheet. Associated with the central volcano is a geothermal field that is just above the top of the shield volcano deposits.

Tectonically the system forms an eastern limit to the faulting of the Tjörnes fracture zone. Other extensional faults in the northern 60 km have had seismic activity consistent with propagation of dykes without eruption in the Holocene.

References

References

1. "Geology".
2. "Geothermal Projects in NE Iceland at Krafla, Bjarnarflag, Gjástykki and Theistareykir".
3. (2019). "Fremrinámar Alternative name: Fremrinámur".
4. "List of Icelandic Volcanoes".
5. (2017). "Geochemistry and petrology of Holocene lavas in Bárðardalur region and their association with the Bárðarbunga volcanic system (Masters dissertation)". Faculty of Earth Sciences, University of Iceland.