MARRYING LARGE IGNEOUS PROVINCES AND MASS EXTINCTION EVENTS: A PERFECT MARRIAGE OR A ROCKY RELATIONSHIP?

Large igneous provinces (LIPs) and large, high-velocity asteroid impacts are two extraordinary and geologically rapid events that are the most plausible causes for mass extinction events. The significance of LIPs to mass extinctions is based on their global distribution, occurring both on continents and in the oceans and throughout Earth’s history, the temporal clustering of numerous LIP events, and the total volume of magma intruded and released on the surface during these geologically brief events. Peak eruptive pulses are often 1–5 Myr long where millions to tens of millions of cubic kilometers of magma are produced. In some cases, at least 1% of the Earth’s surface has been directly covered in volcanic rock, being equivalent to the size of small continents. However, many LIP events do not coincide with major environmental change or a mass extinction. Further, no general correlation exists between the magnitude of the LIP event (or a temporal cluster of LIP events) and the corresponding mass extinction as might be predicted for the severity of an extinction event due to asteroid impact.

Rather than magma volume itself, global environmental disturbance is thought to be caused by aerosol emissions associated with the magmatism. Debate continues as to which volcanic gas(es) are most important in causing climate modification, but recent attention has turned to the potentially substantial quantities of F, Cl, and Br emissions that cause substantial catalytic destruction of stratospheric ozone. An important point is the sustained magmatic and therefore aerosol output, both at individual super-eruption (month to decadal eruption duration) and province scales (>1 Myr) for LIPs. Major asteroid impacts are generally viewed as single-pulse events with effects lasting for up to a few decades. By contrast, the high-frequency (~1000-10,000 yr recurrence intervals) of large magnitude (>M8) basaltic and silicic supereruptions, fed by a substantially larger sub-volcanic intrusive component, which further contribute to aerosol emissions through magma degassing and contact metamorphic effects in sedimentary basins, can collectively provide the opportunity for persistent atmospheric and climatic modification, both at tropospheric and stratospheric levels, environmental stress and prevention of species recovery.