Hekla

Geography & Climate

Hekla is located in Iceland, within the Iceland Neovolcanic Rift Volcanic Province of the broader Atlantic Ocean Volcanic Regions. Situated at 63.98° N, 19.67° W in the Northern Hemisphere, the volcano lies within a subarctic climate zone. With a summit elevation of 1,490 meters above sea level, Hekla 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

Hekla 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 Hekla 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 andesite / basaltic andesite, 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

Hekla has 65 recorded eruptions in the geological database, spanning from 5850 BCE to 2000 CE. The most powerful recorded event was a paroxysmal eruption with devastating regional consequences in 1104 CE, reaching VEI 5 on the Volcanic Explosivity Index. Notable eruptions include 2000 CE (VEI 3), 1991 CE (VEI 3), 1980 CE (VEI 3). With an average interval of roughly 121 years between eruptions over a span of 7,850 years, this is one of the more frequently active volcanoes in the database. This persistent activity suggests a robust and well-supplied magma system beneath the volcano. With eruptive activity as recently as 2000 CE, Hekla remains an actively monitored volcano.

Significance

With a maximum recorded VEI of 5, Hekla has demonstrated the capacity for paroxysmal eruptions comparable to the 1980 eruption of Mount St. Helens. Eruptions of this scale can devastate areas within 20-30 kilometers and produce ash fall that disrupts aviation and agriculture across hundreds of kilometers. Its 65 recorded eruptions make it one of the most prolific volcanoes in the entire global volcanic record, reflecting an exceptionally persistent magma supply system that has sustained near-continuous eruptive activity over millennia. Given its recent activity, Hekla is closely monitored by geological survey organizations to provide early warning of future unrest.

GVP Reference Summary

One of Iceland's most prominent and active volcanoes, Hekla lies near the southern end of the eastern rift zone. Hekla occupies a rift-transform junction, and has produced basaltic andesites, in contrast to the tholeiitic basalts typical of Icelandic rift zone volcanoes. Vatnafjöll, a 40-km-long, 9-km-wide group of basaltic fissures and crater rows immediately SE of Hekla forms a part of the Hekla-Vatnafjöll volcanic system. A 5.5-km-long fissure, Heklugjá, cuts across the 1491-m-high Hekla volcano and is often active along its full length during major eruptions. Repeated eruptions along this rift, which is oblique to most rifting structures in the eastern volcanic zone, are responsible for Hekla's elongated ENE-WSW profile. Frequent large silicic explosive eruptions during historical time have deposited tephra throughout Iceland, providing valuable time markers used to date eruptions from other Icelandic volcanoes. Hekla tephras are generally rich in fluorine and are consequently very hazardous to grazing animals. Extensive lava flows from historical eruptions, which date back to 1104 CE, cover much of the volcano's flanks.

— Smithsonian Institution, Global Volcanism Program