Buoyant plumes driven by basaltic fire fountains are modeled.
1986 Izu-Oshima basaltic fissure eruption with 12–16 km plume is used to test model.
Roza eruption 15 Ma ago could have injected 62 Mt of SO2/day into the stratosphere.
Roza fissure could have supported 30–40 explosive phases 3–4 days long over decades.
Model results can be used as input for 3-D climate models to quantify the impact.