Environmental Impact of Silicic Magmatism in Large Igneous Province Events

Abstract

Silicic magmatism is a feature of all continental LIP events, and where volumetrically significant, occurs as high‐frequency (~1,000–10,000 yr recurrence intervals), large‐magnitude (>M8) explosive supereruptions producing vast ignimbrite sheets. Silicic supereruptions inherently have the eruptive mechanism to deliver aerosols and ash to the stratosphere for global dispersal, and thus overcome eruptive barriers that exist for flood basalts built up by long‐lived, low effusion and low vigor fountains that lack height and persistent stratospheric penetration. The historical record demonstrates the climate forcing capabilities of silicic supereruptions, which during LIP events, were likely associated with large CO2, SO2, halogen, and Hg emissions, and through tephra deposition, could cause iron fertilization in the world's oceans, thereby kick‐starting phytoplanktonic biological pumps to significantly draw down atmospheric CO2. What may be important, therefore, for LIP events to cause the most environmental impact and trigger a mass extinction, is the combined effect of closely spaced basaltic and silicic, or effusive and explosive, eruptions that work in tandem to overload the troposphere and stratosphere with volcanic aerosols producing rapid decadal‐scale, extreme fluctuations in pH driven by acid rain, S‐, or iron fertilization‐driven temperature chills, and toxic UV radiation bursts. These effects could be repeated within as little as a few hundred years of each other particularly during hyperactive LIP pulses.