A
fissure vent, also known as a
volcanic fissure or
eruption fissure, is a linear
volcanic vent through which
lava erupts, usually without any
explosive activity. The vent is often a few meters wide and may be many kilometers long. Fissure vents can cause large
flood basalts which run first in
lava channels and later in
lava tubes. After some time the eruption builds up
spatter resp. ash cones and may concentrate on one or some of them. Small fissure vents may not be easily discernible from the air, but the crater rows (see
Laki) or the canyons (see
Eldgjá) built up by some of them are.