Gas Fluxes from Flood Basalt Eruptions

Subaerial continental flood basalt volcanism is distinguished from all other volcanic activity by the repeated effusion of huge batches of basaltic magma (∼10²-10³ km³ per eruption) over short periods of geologic time (<1 Myr). Flood basalt provinces are constructed of thick stacks of extensive pahoehoe-dominated lava flow fields and are the products of hundreds of eruptions. Each huge eruption comes from a dyke-fed fissure tens to hundreds of kilometres long and lasts about a decade or more. Such spatial and temporal patterns of lava production do not occur at any other time in Earth history, and, during eruptions, gas fluxes of ∼1 Gt per year of SO₂ and CO₂ over periods of a decade or more are possible. Importantly, the atmospheric cooling associated with aerosols generated from the SO₂ emissions of just one flood basalt eruption is likely to have been severe and would have persisted for a decade or longer. By contrast, warming due to volcanogenic CO₂ released during an eruption is estimated to have been insignificant because the mass of CO₂ would have been small compared to that already present in the atmosphere.