Assessing eruption column height in ancient flood basalt eruptions

• Published in: Earth and planetary science letters Vol. 457; pp. 263 - 270
• Main Authors: Glaze, Lori S., Self, Stephen, Schmidt, Anja, Hunter, Stephen J.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.01.2017
• Subjects: Basalt; Buoyancy; climate; Columbia River Basalt Group; Cracks; flood basalt; Floods; Mathematical models; plume heights; Plumes; Roza; Segments; Stratosphere; sulfur dioxide; Philippines, Luzon I., Mount Pinatubo; USA, Columbia R; sulfur dioxide; Columbia River Basalt Group; Roza; plume heights; climate; flood basalt
• DOI: 10.1016/j.epsl.2014.07.043
• ISSN: 0012-821X

A buoyant plume model is used to explore the ability of flood basalt eruptions to inject climate-relevant gases into the stratosphere. An example from the 1986 Izu-Oshima basaltic fissure eruption validates the model's ability to reproduce the observed maximum plume heights of 12–16 km above sea level, sustained above fire-fountains. The model predicts maximum plume heights of 13–17 km for source widths of between 4–16 m when 32% (by mass) of the erupted magma is fragmented and involved in the buoyant plume (effective volatile content of 6 wt%). Assuming that the Miocene-age Roza eruption (part of the Columbia River Basalt Group) sustained fire-fountains of similar height to Izu-Oshima (1.6 km above the vent), we show that the Roza eruption could have sustained buoyant ash and gas plumes that extended into the stratosphere at ∼45°N. Assuming 5 km long active fissure segments and 9000 Mt of SO2 released during explosive phases over a 10–15 year duration, the ∼180km of known Roza fissure length could have supported ∼36 explosive events/phases, each with a duration of 3–4 days. Each 5 km fissure segment could have emitted 62 Mt of SO2 per day into the stratosphere while actively fountaining, the equivalent of about three 1991 Mount Pinatubo eruptions per day. Each fissure segment could have had one to several vents, which subsequently produced lava without significant fountaining for a longer period within the decades-long eruption. Sensitivity of plume rise height to ancient atmospheric conditions is explored. Although eruptions in the Deccan Traps (∼66Ma) may have generated buoyant plumes that rose to altitudes in excess of 18 km, they may not have reached the stratosphere because the tropopause was substantially higher in the late Cretaceous. Our results indicate that some flood basalt eruptions, such as Roza, were capable of repeatedly injecting large masses of SO2 into the stratosphere. Thus sustained flood basalt eruptions could have influenced climate on time scales of decades to centuries but the location (i.e., latitude) of the province and relevant paleoclimate is important and must be considered. •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.