Flood Basalts Don't Cause Mass Extinctions Through Sulphuric Acid

Selective environmental stress from sulphur emitted by continental flood basalt eruptions

Authors:

Schmidt et al

Abstract:

Several biotic crises during the past 300 million years have been linked to episodes of continental flood basalt volcanism, and in particular to the release of massive quantities of magmatic sulphur gas species. Flood basalt provinces were typically formed by numerous individual eruptions, each lasting years to decades. However, the environmental impact of these eruptions may have been limited by the occurrence of quiescent periods that lasted hundreds to thousands of years. Here we use a global aerosol model to quantify the sulphur-induced environmental effects of individual, decade-long flood basalt eruptions representative of the Columbia River Basalt Group, 16.5–14.5 million years ago, and the Deccan Traps, 65 million years ago. For a decade-long eruption of Deccan scale, we calculate a decadal-mean reduction in global surface temperature of 4.5 K, which would recover within 50 years after an eruption ceased unless climate feedbacks were very different in deep-time climates. Acid mists and fogs could have caused immediate damage to vegetation in some regions, but acid-sensitive land and marine ecosystems were well-buffered against volcanic sulphur deposition effects even during century-long eruptions. We conclude that magmatic sulphur from flood basalt eruptions would have caused a biotic crisis only if eruption frequencies and lava discharge rates had been high and sustained for several centuries at a time.

Does Mars Have ACID Fog?!

Soshanna Cole, an assistant professor at Ithaca College, appears to have discovered evidence of acidic fog altering the surface of Mars. The discovery was made via an analysis of data collected by NASA's Spirit rover over the course of its exploration of the Red Planet.

Spirit landed on Mars in January 2004, and, prior to becoming embedded in soft soil, made numerous breakthroughs that revolutionized our understanding of Mars. Eventually, the rover stopped transmitting, with the last communication with the robotic pioneer taking place on March 22, 2010.

As is so often the case with NASA's flagship missions, Spirit is living up to its name, and continuing to provide insights into the Martian environment long after falling into its perennial slumber.

Cole analyzed data collected by Spirit from a dozen locations in the Cumberland Ridge and the Husband Hill summit focusing on "watchtower class" rocky outcrops. It was discovered that the formations exhibited notable abnormalities that hinted at a strangely Earth-like process occurring on the Red Planet.

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Evidence of Significant Acid Rain Pulses During Permian Triassic Extinction From Italy

Terrestrial acidification during the end-Permian biosphere crisis?

Authors:

Sephton et al

Abstract:

Excessive acid rainfall associated with emplacement of the Siberian Traps magmatic province is increasingly accepted as a major contributing factor to the end-Permian biosphere crisis. However, direct proxy evidence of terrestrial acidification is so far not available. In this paper, we seek to determine the probability that relative proportions of extractable monophenolic components from soil-derived organic matter in marine sediments provide a molecular proxy for estimating soil acidity. Intermittently low and high ratios of vanillic acid to vanillin detected in latest Permian and earliest Triassic deposits of the southern Alps, Italy, support concepts of pulses of severe acidification (pH less than 4) during the main phase of the biosphere crisis.

Was Acid Rain the Kill Mechanism of the KT/K-Pg Extinction Brought on by the Chicxulub Impact?

Production of sulphate-rich vapour during the Chicxulub impact and implications for ocean acidification

Authors:

Ohno et al

Abstract:

The mass extinction event at the Cretaceous/Palaeogene boundary 65.5 Myr ago has been widely attributed to the Chicxulub impact, but the mechanisms of extinction remain debated. In the oceans, near-surface planktonic foraminifera suffered severe declines, in contrast to the relatively high survival rates of bottom-dwelling benthic foraminifera. The vapour produced by an impact into Chicxulub’s target rocks, which include sulphate-rich anhydrite, could have led to global acid rain, which can explain the pattern of oceanic extinctions. However, it has been suggested that most of the sulphur in the target rocks would have been released as sulphur dioxide and would have stayed in the stratosphere for a long time. ere we show, from impact experiments into anhydrite at velocities exceeding 10 km s−1, that sulphur trioxide dominates over sulphur dioxide in the resulting vapour cloud. Our experiments suggest that the Chicxulub impact released a huge quantity of sulphur trioxide into the atmosphere, where it would have rapidly combined with water vapour to form sulphuric acid aerosol particles. We also find, using a theoretical model of aerosol coagulation following the Chicxulub impact, that larger silicate particles ejected during the impact efficiently scavenge sulphuric acid aerosol particles and deliver the sulphuric acid to the surface within a few days. The rapid surface deposition of sulphuric acid would cause severe ocean acidification and account for preferential extinction of planktonic over benthic foraminifera.