Fissure Flames

Short answer: A fissure eruption happens when a dike, a vertical sheet of magma forced up through the crust, reaches the surface along a crack. Lava then erupts from many points along a line at once, often as a row of lava fountains that the USGS calls a 'curtain of fire'.

Most fissure eruptions involve runny basalt and are effusive, meaning lava pours out rather than exploding. The National Park Service rates them at 0 to 1 on the Volcanic Explosivity Index. So the main products are lava fountains, spatter and gas, not big ash columns. Spatter piling up along the crack builds low ramparts and spatter cones, so a fissure can leave a row of small craters rather than one tall cone. Fissures range from a few hundred meters to tens of kilometers long. Iceland's Laki (Lakagígar) eruption began on June 8, 1783, from a fissure system about 27 km long with more than 130 craters. Feeder dikes for the Columbia River flood basalts reach as much as 180 km. Fissure eruptions are common where plates pull apart, as in Iceland, which sits on the Mid-Atlantic Ridge. They also happen along rift zones on the flanks of hot-spot shield volcanoes like Kīlauea and Mauna Loa, and in volcanic fields in the middle of continents. The footage shows a line of lava fountains beside a gas plume, with a fresh lava field on either side. The source doesn't name the eruption, so the case doesn't either.