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] There is a central high temperature geothermal area with numerous steam vents and fumaroles.

Around 9500 BCE, an eruption produced approximately 18 billion cubic metres of basaltic lava.