Torfajokull

Geography & Climate

Torfajokull is located in Iceland, within the Iceland Neovolcanic Rift Volcanic Province of the broader Atlantic Ocean Volcanic Regions. Situated at 63.89° N, 19.12° W in the Northern Hemisphere, the volcano lies within a subarctic climate zone. With a summit elevation of 1,280 meters above sea level, Torfajokull is a moderately sized peak that remains accessible to hikers and researchers for much of the year. The volcanic landform is characterized as a composite, which describes the physical shape and structure of the volcanic edifice as observed from the surface.

Geological Context

Torfajokull 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 Torfajokull 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 rhyolite, a silica-rich volcanic rock associated with highly viscous magma. Rhyolitic eruptions can be extremely explosive and are responsible for some of the largest volcanic events in Earth's history, including supervolcanic caldera-forming eruptions. The high silica content traps dissolved gases, building enormous pressure that can lead to catastrophic explosive releases.

Eruption History Summary

Torfajokull has 10 recorded eruptions in the geological database, spanning from 6050 BCE to 1477 CE. The most powerful recorded event was a severe eruption capable of regional ash fall and pyroclastic flows in 870 CE, reaching VEI 3 on the Volcanic Explosivity Index. Notable eruptions include 870 CE (VEI 3), 150 CE (VEI 3). This level of eruptive frequency indicates a persistently active volcanic system that warrants ongoing monitoring.

Significance

With a maximum recorded VEI of 3, Torfajokull has produced eruptions capable of generating pyroclastic flows and significant ash fall in the surrounding area. While not among the largest eruptions globally, VEI 3 events pose serious hazards to local populations and can disrupt regional air travel. With 10 recorded eruptions, Torfajokull has a substantial eruptive history that provides valuable data for understanding volcanic behavior and assessing future hazards in the Atlantic Ocean Volcanic Regions region.

GVP Reference Summary

The Torfajökull central volcano, located north of Myrdalsjökull and south of Thorisvatn lake, is cut by a 12-km-wide caldera that formed during the Pleistocene. With about 225 km3 of silicic extrusive rocks exposed, it comprises the largest area of silicic and intermediate volcanism in Iceland. Work by Moles et al. (2019) identified the Ring Fracture Rhyolites as the source of the rhyolitic and trachyandesitic Thórsmörk Ignimbrite and the II-RHY-1 tephra, and dated them at 51.3 ± 4.2 ka (40Ar/39Ar). The dominantly rhyolitic complex rises about 500 m above surrounding basaltic plains and is elongated WNW-ESE. Most rhyolitic lava flows were erupted subglacially, with silicic hyaloclastites that form ridge and dome-shaped breccias. During postglacial times only a narrow fissure zone at the western end has been active, producing mostly silicic lava flows, domes, and tephras. The most recent silicic eruption produced the Hrafntinnuhraun flow about 900 CE. The fissure system is along trend with and was active at the same time as the basaltic Veidivötn fissure system of Bárdarbunga central volcano in 1477 CE. The small Torfajökull icecap lies mostly outside the SE rim of the caldera, which is the site of vigorous thermal activity over a broad area of 130-140 km2.

— Smithsonian Institution, Global Volcanism Program