Bárðarbunga is a subglacial stratovolcano located under the ice cap of Vatnajökull glacier within the Vatnajökull National Park in Iceland. It rises to 2,009 metres (6,591 ft) above sea level, making it the second highest mountain in Iceland, about 101 metres (331 ft) lower than Hvannadalshnjúkur. The caldera is about 80 square kilometres, up to 10 km wide and about 700 metres (2,300 ft) deep. The surrounding edges rise up to 1,850 metres but the base is on average close to 1,100 metres. The volcano is covered in ice to a depth of 850m, hiding the glacier-filled crater. The associated volcanic system and fissure swarm is about 190 km long and 25 km wide.
Bárðarbunga was a little-known volcano in Iceland due to its remote location and infrequent eruptions approximately once every 50 years, but recent studies have shown that many tephra layers originally thought to be from other volcanoes were ejected from Bárðarbunga.
Sustained seismic activity has been gradually increasing in Bárðarbunga and its associated northern fissure system for a seven years' period, starting in 2007 and leading to an eruption only towards the end of 2014. This activity decreased after the Grímsvötn eruption in 2011, but later returned to a similar level as before the eruption. The prior eruption was in 1910. There has been frequent volcanic activity outside the glacier to the southwest in the highlands between Vatnajökull and Mýrdalsjökull, and also to the northeast toward