Oddnyjarhnjukur-Langjokull

Geography & Climate

Oddnyjarhnjukur-Langjokull is located in Iceland, within the Iceland Neovolcanic Rift Volcanic Province of the broader Atlantic Ocean Volcanic Regions. Situated at 64.85° N, 19.70° W in the Northern Hemisphere, the volcano lies within a subarctic climate zone. With a summit elevation of 1,100 meters above sea level, Oddnyjarhnjukur-Langjokull is a moderately sized peak that remains accessible to hikers and researchers for much of the year. The volcanic landform is characterized as a cluster, which describes the physical shape and structure of the volcanic edifice as observed from the surface.

Geological Context

Oddnyjarhnjukur-Langjokull is situated along a rift zone, where tectonic plates are pulling apart. As the crust thins and fractures, magma rises to fill the gap, creating volcanic activity. Rift volcanism typically produces more fluid lava flows rather than explosive blasts, which means communities near Oddnyjarhnjukur-Langjokull in Iceland generally face slower-moving hazards like lava flows and ground fissures rather than sudden pyroclastic events. However, rift volcanoes can still generate significant ash emissions and gas releases that affect local air quality. The dominant rock type is basalt / picro-basalt, a dark, fine-grained volcanic rock that forms from rapidly cooling, low-viscosity lava. Basaltic eruptions tend to be less explosive and produce fluid lava flows that can travel long distances. While less immediately dangerous than explosive eruptions, basaltic lava flows can destroy structures and infrastructure in their path, and volcanic gases released during these eruptions can affect air quality over a wide area.

Eruption History Summary

Oddnyjarhnjukur-Langjokull has 6 recorded eruptions in the geological database, spanning from 8600 BCE to 950 CE. The most powerful recorded event was an explosive event producing ash plumes up to several kilometers in 950 CE, reaching VEI 2 on the Volcanic Explosivity Index. This eruption frequency indicates a moderately active volcanic system with periodic reawakenings.

Significance

With 6 recorded eruptions on file, Oddnyjarhnjukur-Langjokull has enough documented activity to help scientists identify patterns in its eruptive behavior.

GVP Reference Summary

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.

— Smithsonian Institution, Global Volcanism Program