Bárðarbunga is a subglacial stratovolcano located under the ice cap of Vatnajökull glacier within the Vatnajökull National Park in Iceland. It rises to above sea level, making it the second highest mountain in Iceland, about lower than Hvannadalshnjúkur. The caldera is about 80 square kilometres, up to 10 km wide and about 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.