The end-Triassic extinction: A tale of Death and Global Warming.

A basaltic lava flow section from the Middle Atlas, Morocco. From Wikimedia Commons.

For the last 540 million years, five mass extinction events shaped the history of the Earth. The End-Triassic Extinction (ETE) is typically attributed to climate change associated with degassing of basalt flows from the central Atlantic magmatic province (CAMP) emplaced during the initial rifting of Pangea. Most mammal-like reptiles and large amphibians disappeared, as well as early dinosaur groups. In the oceans, this event eliminated conodonts and nearly annihilated corals, ammonites, brachiopods and bivalves.

The emplacement of CAMP started c. 100,000 years before the end-Triassic event and continued in pulses for 700,000 years. Three negative organic C-isotope excursions (CIEs) have being recognized at the end-Triassic: the Marshi, the Spelae, and the top-Tilmanni CIEs. A recent study published in Nature estimated that a single short-lived magmatic pulse would have released about 5 × 1016 mol CO2, roughly the same total amount of projected anthropogenic emissions over the 21st century, causing an increase of about 2 °C in global temperatures, and an oceanic pH decrease of about 0.15 units over 0.1 kyrs, suggesting that the end-Triassic climatic and environmental changes, driven by CO2 emissions, may have been similar to those predicted for the near future.

A normal fern spore compared with mutated ones from the end-Triassic mass extinction event. Image credit: S LINDSTRÖM, GEUS

These massive volcanic eruptions with lava flows, also released large quantities of sulphur dioxide, thermogenic methane and large amounts of HF, HCl, halocarbons and toxic aromatics and heavy metals into the atmosphere, resulting in global warming, and ozone layer depletion. The high concentrations of pCO2 are indicative of ocean acidification suggesting that this may have been a marine extinction mechanism especially in relation to the scleractinian corals. Mutagenesis observed in plants and their reproductive cells (spores and pollen) were likely caused by mercury, the most genotoxic element on Earth .

The new study confirms the abundance of CO2 (up to 105 Gt volcanic CO2 degassed during CAMP emplacement) and indicates that at least part of this carbon has a middle- to lower-crust or mantle origin, suggesting that CAMP eruptions were rapid and potentially catastrophic for both climate and biosphere. Since the industrial revolution, the wave of animal and plant extinctions that began with the late Quaternary has accelerated. Australia has lost almost 40 percent of its forests, and almost 20% of the Amazon has disappeared in last five decades.Calculations suggest that the current rates of extinction are 100–1000 times above normal, or background levels. If we want to stop the degradation of our planet, we need to act now.

 

References:

Capriolo, M., Marzoli, A., Aradi, L.E. et al. Deep CO2 in the end-Triassic Central Atlantic Magmatic Province. Nat Commun 11, 1670 (2020). https://doi.org/10.1038/s41467-020-15325-6

Sofie Lindström et al. Volcanic mercury and mutagenesis in land plants during the end-Triassic mass extinction, Science Advances (2019). DOI: 10.1126/sciadv.aaw4018}

Davies, J., Marzoli, A., Bertrand, H. et al. End-Triassic mass extinction started by intrusive CAMP activity. Nat Commun 8, 15596 (2017). https://doi.org/10.1038/ncomms15596

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