News Release 

Asteroid impact killed dinosaurs while volcanism shaped life in the aftermath

American Association for the Advancement of Science

Researchers who analyzed well-preserved ocean drilling and global temperature records have added support to the idea that the primary cause of the Cretaceous-Paleogene (K/Pg) mass extinction was an asteroid impact, rather than extreme volcanism. Their new study evaluates the impact of greenhouse outgassing by volcanism in the Deccan Traps on global temperature. According to their results, volcanic gasses may have played an important role in shaping the rise of different species after the extinction, rather than driving the initial event. Sixty-six million years ago, two planetary-scale catastrophic events - an asteroid impact and large-scale volcanism - ravaged Earth's surface as well as most of the terrestrial lifeforms that walked upon it, bringing the long reign of the dinosaurs to a close. Disentangling the relative effects of the large amounts of lava from the Deccan traps and the asteroid impact that occurred across the Cretaceous-Paleogene (K/Pg) mass extinction has been challenging and the cause of the K/Pg extinction remains uncertain. Unlike previous studies on the role of Deccan volcanism, which largely focused on the accumulation of lava, Pincelli Hull and colleagues evaluated the more environmentally relevant aspect of the eruption - outgassing. Hull et al. investigated the timing of Deccan outgassing by modeling, in several scenarios, the effects of carbon dioxide and sulfur emissions on long-term global temperatures. They compared the results to global paleotemperature records spanning the K/Pg extinction event. The results suggest that at least 50% or more of the major Deccan outgassing occurred well before the impact, not just before it. Therefore, only the impact coincided with the mass extinction event, they say. The timing of this outgassing they propose would have led to changes in the carbon cycle that allowed the ocean to absorb vast quantities of carbon dioxide, potentially limiting global warming that would otherwise be expected from post-extinction Deccan volcanism. "Deccan volcanism might have contributed to shaping [the rise of Cenozoic species and communities] during the extinction aftermath," the authors say.

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