A fissure vent, also known as a volcanic fissure, eruption fissure or simply a fissure, is a linear volcanic vent through which lava erupts, usually without any explosive activity. The vent is often a few metres wide and may be many kilometres long. Fissure vents can cause large flood basalts which run first in lava channels and later in lava tubes. After some time, the eruption tends to become focused at one or more spatter cones. Small fissure vents may not be easily discernible from the air, but the crater rows or the canyons built up by some of them are.

Bárðarbunga, is an active stratovolcano located under Vatnajökull in Vatnajökull National Park which is Iceland's most extensive glacier. The second highest mountain in Iceland, 2,000 metres (6,600 ft) above sea level, Bárðarbunga is also part of the Bárðarbunga-Veiðivötn volcanic system that is approximately 190 kilometres (120 mi) long and 25 kilometres (16 mi) wide.