Oddnýjarhnjúkur-Langjökull

The Oddnýjarhnjúkur-Langjökull system includes the Hveravellir central volcano at the northern end of this active volcanic zone that extends NE from the Reykjanes Peninsula. Hveravellir occupies the NE half of the massive Langjökull icecap, east of the Pleistocene Erikskökull table mountain. A summit caldera lies beneath the ice. The Kjalhraun shield volcano east of Langjökull produced about 11 km3 of lava around 7,800 years ago. Several small shield volcanoes have been constructed along flank fissure zones, producing postglacial lava flows on the N, W, and E sides of Langjökull. One of the most prominent of these is a small shield volcano at the site of the massive Hallmundahraun lava flow, which covers about 240 km2 and was erupted about 950 CE. The Geysir thermal area lies in the Haukadalur basin, near the southern end of the fissure system. The classic Icelandic shield volcano Skjaldbreidur is also within the southern part of this system, between Thorsjökull glacier and Thingvallavatn lake; the broad, low-angle volcano produced more than 13 km3 of basaltic lava flows during the early Holocene.