Theistareykjarbunga

Theistareykjarbunga (Þeistareykjarbunga, ) is a shield volcano in north-eastern Iceland with two fissure vents called Þeistareykjahraun and Borgahraun, and two cones: the 370 m Stórahversmór  and the 540 m, 30 km3 Stóravíti. They both are currently extinct, although there is evidence suggesting the potential for activity such as recent localised uplift and seismicity. The multiple vents make up the Theistareykir (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. The recent lava has picrite, olivine tholeiite basalt characteristics but before the ice age there were basaltic andesite and rhyolite eruptions. There is a central high temperature geothermal area with numerous steam vents and fumaroles. This has been utilised by a 90 MWe power station.

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.