A volcanic eruption where lava—usually very fluid and basic—wells up through fissures in the Earth’s crust and spreads over a large area. See Walker (1995) Geol. Soc. Memoirs 16 on the Antrim plateau, Northern Ireland; see also Mege (2004) J. Volcan. & Geothermal Res. 131, 1 on fissure eruptions and dyke fracture length.