An impact with a dash of volcanism Around the time of the end-Cretaceous mass extinction that wiped out dinosaurs, there was both a bolide impact and a large amount of volcanism. Hull et al. ran several temperature simulations based on different volcanic outgassing scenarios and compared them with temperature records across the extinction event. The best model fits to the data required most outgassing to occur before the impact. When combined with other lines of evidence, these models support an impact-driven extinction. However, volcanic gases may have played a role in shaping the rise of different species after the extinction event. Science, this issue p. 266 The primary cause of the end-Cretaceous mass extinction was an impact, with volcanism playing a role in the aftermath. The cause of the end-Cretaceous mass extinction is vigorously debated, owing to the occurrence of a very large bolide impact and flood basalt volcanism near the boundary. Disentangling their relative importance is complicated by uncertainty regarding kill mechanisms and the relative timing of volcanogenic outgassing, impact, and extinction. We used carbon cycle modeling and paleotemperature records to constrain the timing of volcanogenic outgassing. We found support for major outgassing beginning and ending distinctly before the impact, with only the impact coinciding with mass extinction and biologically amplified carbon cycle change. Our models show that these extinction-related carbon cycle changes would have allowed the ocean to absorb massive amounts of carbon dioxide, thus limiting the global warming otherwise expected from postextinction volcanism.

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跨越白垩纪-古近纪边界的撞击和火山作用

带有少量火山作用的撞击在导致恐龙灭绝的白垩纪末大灭绝前后，既有火流星撞击，也有大量火山作用。赫尔等人。基于不同的火山除气情景运行了几次温度模拟，并将它们与整个灭绝事件的温度记录进行了比较。最好的模型适合在撞击前发生的最需要放气的数据。当与其他证据线结合时，这些模型支持影响驱动的灭绝。然而，火山气体可能在灭绝事件后塑造不同物种的崛起中发挥了作用。科学，这个问题 p。266 白垩纪末大灭绝的主要原因是撞击，火山活动在后果中发挥了作用。白垩纪末大灭绝的原因引起了激烈的争论，由于边界附近发生了非常大的火流星撞击和洪水玄武岩火山作用。由于杀戮机制和火山释放、撞击和灭绝的相对时间的不确定性，解开它们的相对重要性变得复杂。我们使用碳循环模型和古温度记录来限制火山释放气体的时间。我们发现支持在撞击之前明显开始和结束的主要释气，只有撞击与大规模灭绝和生物放大的碳循环变化同时发生。我们的模型表明，这些与灭绝相关的碳循环变化将使海洋吸收大量二氧化碳，从而限制了灭绝后火山活动所预期的全球变暖。