Geological features near the Theistareykjarbunga volcanic system (red outlines). Other shading shows: calderas, central volcanoes and fissure swarms, subglacial terrain above 1,100 m (3,600 ft), and seismically active areas. Clicking on the image enlarges to full window and enables mouse-over with more detail.
Theistareykjarbunga (Þeistareykjarbunga, Icelandic pronunciation:[ˈθeistaˌreiːcarˌpuŋka]ⓘ) is a shield volcano in north-eastern Iceland with two fissure vents called Þeistareykjahraun [ˈθeiːstaˌreiːcaˌr̥œyːn] and Borgahraun [ˈpɔrkaˌr̥œyːn], and two cones: the 370 m (1,210 ft) Stórahversmór [ˈstouːraˌkʰvɛr̥sˌmouːr̥] and the 540 m (1,770 ft), 30 km3 (7.2 cu mi) Stóravíti [ˈstouːraˌviːtɪ]. They both are currently extinct,[1] although there is evidence suggesting the potential for activity such as recent localised uplift and seismicity.[2] The multiple vents make up the Theistareykir[1] (Þeistareykir) volcanic system, with more recent evidence that the former classification as a shield volcano is better considered an embryonic central volcano with associated fissure swarm, as rhyolite has erupted in a limited area.[3] The recent lava has picrite, olivinetholeiite basalt characteristics but before the ice age there were basaltic andesite and rhyolite eruptions.[3] There is a central high temperature geothermal area with numerous steam vents and fumaroles.[3] This has been utilised by a 90 MWe power station.[2]
Eruptions
There have been three dated eruptions, all VEI-0: the most recent eruption was around 900 BCE and the previous eruption was in 6800 BCE. Around 9500 BCE, an eruption produced approximately 18 billion cubic metres of basaltic lava.[1]
^ abcGrönvold, K.; Sæmundsson, K. (2019). "Catalogue of Icelandic Volcanoes:Þeistareykir". Icelandic Meteorological Office, Institute of Earth Sciences at the University of Iceland, Civil Protection Department of the National Commissioner of the Iceland Police. Retrieved 28 January 2024.
