Meet the Volcanoes
More at: Catalogue of Icelandic Volcanoes
Reykjanes and Svartsengi
The Reykjanes volcanic system has been moderately active with the last eruption occurring in 1240 CE. It is about 45 km long and 5-15 km wide, with a SW-NE trend. Its northern part merges with the Svartsengi volcanic system while the southernmost 9 km are below sea level. During the Holocene more than 15 eruptions have occurred (VEI 1-3), producing basalts and characterized by lava flows on land and surtseyan explosive activity offshore.
The Svartsengi volcanic system has displayed similar activity as Reykjanes with the last eruption at about 1240 CE. The system is at least 30 km long and 7 km wide. Activity during the Holocene has been effusive, producing lava flows.
The Holocene eruption histories of the Svartsengi and Reykjanes volcanic systems seem to be analogous; volcanic episodes (Fires) in the western Reykjanes Peninsula include both of the systems, with the most recent Fires lasting from 1210 to 1240 CE. In light of the geological similarities the Reykjanes and the Svartsengi the systems are here described together.
Activity level: Moderate
Krýsuvík
The Krýsuvík-Trölladyngja volcanic system on the Reykjanes Volcanic Zone has been moderately active in the Holocene (last 8000 years). The last eruption started on the 19th of March 2021 after about 870 years of repose. It takes place on a secondary swarm of the Krýsuvík-Trölladyngja system, called Fagradalsfjall that is sometimes considered a separate volcanic system. The last eruptive episode before the 2021 eruption, consisting of two eruptions separated by 37 years, occurred in the 12 century CE, the lava flows reaching to the sea on the north and south coast of the peninsula.
The NE-SW trending volcanic system comprises a 50 km long, composite fissure swarm without a developed central volcano. Maximum elevation is ~400 m a.s.l. The system has no ice cover but a large lake lies within the system.
The characteristic activity is effusive basaltic eruptions producing lava flows covering some tens of km2 and minor tephra deposits. Eruption frequency during the last 3000 years is 1 eruption per 750 years.
Activity level: Moderate
Öræfajökull
Öræfajökull, Orafajokul, (Icelandic pronunciation: [ˈœːraivaˌjœːkʏtl̥]) is an ice-covered volcano in south-east Iceland. The largest active volcano and the highest peak in Iceland at 2,110 metres (6,920 ft), it lies within the Vatnajökull National Park and is covered by the glacier.
The Öræfajökull volcanic system has been moderately active in the Holocene. The last eruption was a moderate explosive eruption in 1727 CE. The Öræfajökull system lies on a volcanic belt outside the main volcanic zones and consists of a central volcano about 20 km in diameter, rising to 2110 m a.s.l. The central volcano is covered by ice above 1000 m a.s.l. and has 3x4 km ice-filled caldera at the summit.
The characteristic activity is explosive silicic eruptions with tephra volumes (bulk volume) ranging from 0.1-10.0 km3. Eruption frequency during the last 1000 years is 1 eruption per 500 years. Eruptions are accompanied by jökulhlaups.
Waking up from a slumber
In 2016 geologists began detecting changes in the area. Seismic activity began picking up, with several sharp tremors and earthquake swarms, rising geothermal activity and significant uplift have also been detected. These developments all point to magma pushing its way into the upper layers of the earths crust. Since the activity began the Icelandic Meteorological Office has stepped up its monitoring of the volcano.
To date the magma movements are believed to be relatively small, significantly smaller than what was seen in the lead up to the 2010 Eyjafjallajökull eruption. However, it is large enough to cause the creation of a new powerful geothermal area in the volcano's caldera, capable of melting a deep cauldron in the ice cap.
Monitoring is ongoing.
Activity level: Moderate
Grímsvötn
Description
The Grímsvötn volcanic system is the most active in Iceland in Holocene time. The last eruption occurred in 2011 CE and emitted about 0.8 km3 of basaltic tephra (bulk volume). It consists of a central volcano and a fissure swarm, about 100 km long and 18 km wide, rising to 1700 m a.s.l. and is part of the Eastern Volcanic Zone. It is partly covered by up to 700 m thick ice and the central volcano has an 8×10 km ice-filled caldera.
Characteristic activity on the ice-covered part is explosive basaltic eruptions with tephra volumes of 0.01-1.0 km3 and on the ice-free part basaltic fissure eruptionswith lava volumes up to 15 km3. Eruption frequency during the last 1100 years is 1 eruption per 10 years. Eruptions are accompanied by jökulhlaups.
The Þórðarhyrna (e: Thordarhyrna) central volcano has often been considered to belong to the Grímsvötn system but is treated separately here.
Activity level: High
Bárðarbunga
Description
The Bárðarbunga volcanic system has been highly active in the Holocene with at least 26 eruptions in the last 11 centuries. The most recent eruption was a large subaerial fissure eruption (lava volume 1.6 km3) from August 2014 to February 2015 in Holuhraun area north of Vatnajökull glacier. Several minor subglacial eruptions may also have occurred in the two week period prior to the main eruption.
The Bárðarbunga system lies on the Eastern Volcanic Zone and is about 190 km long and up to 25 km wide, consisting of a central volcano rising to 2009 m a.s.l. and a fissure swarm partly covered by the Vatnajökull ice cap. The central volcano has a 65 km2 ice-filled caldera. The characteristic activity is explosive basaltic eruptions occurring on central volcano flanks or the fissure swarm.
Known eruptions have mostly been VEI 3-4 but occasionally VEI 5-6 (bulk volume of tephra up to 10 km3). The largest eruptions occurred in the early Holocene, effusive basaltic eruptions on the fissure swarm with lava volumes ≥20 km3. Eruption frequency during the last 1100 years is 1 eruption per 50 years on average. Eruptions on the ice covered part of the system have the potential to cause major floods in several rivers flowing southwards and northwards from the Vatnajökull ice cap.
Activity level: High
Hekla
Description
The Hekla volcanic system has been highly active in the Holocene. The last eruption occurred in 2000 CE and it is the third most active in Iceland in the last millennium with 23 eruptions (VEI 0-5).
The Hekla system belongs to the Eastern Volcanic Zone and consists of a central volcano rising to 1490 m a.s.l. and a about 60 km long fissure swarm. Eruption frequency is highest at the Hekla central volcano, which typically produces mixed eruptions with tephra and lava of silicic to intermediate composition. They feature a short plinian or subplinian opening phase (VEI 2-4) followed by lava effusion.
The preceding repose commands the SiO2 content of the first erupted magma (the magnitude of the opening phase) and the volumes erupted - the shorter the repose the smaller the following eruption.
About 100 eruptions are known in the last 9000 years, ranging from purely explosive to purely effusive. The largest explosive eruptions (VEI 6) occurred 4300 and 3000 years ago.
Activity level: High
Katla
Description
The partly ice covered Katla volcanic system has been highly active in the Holocene with at least 21 eruption in the last 1100 years. The last eruption to break through the ice took place in 1918 CE.
The Katla system lies on the Eastern Volcanic Zone and is about 80 km long, consisting of a central volcano rising to 1500 m a.s.l. and an active fissure swarmextending towards northeast. The central volcano is partly covered by up to 700 m thick ice and has an 9x14 km ice-filled caldera.
The characteristic activity is explosive basaltic eruptions at the Katla central volcano with tephra volumes (bulk volume) ranging from 0.02 to over 2 km3, accompanied by jökulhlaups with maximum discharge of up to 300,000 m3/sec. The largest eruptions are effusive basaltic eruptions on the fissure swarm with lava volumes ≥18 km3. Eruption frequency during the last 1100 years is 1 eruption per 50 years.
Activity level: High
More info see Katla Geopark