2022-09-12 カリフォルニア大学バークレー校(UCB)
Lava fountaining above the volcanic fissure of the Holuhraun flood lava eruption in Iceland in September 2014, a small-scale analog to the eruptions in the Deccan Traps, 66 million years ago. (Photo credit: Michelle Parks, University of Iceland)
新しい研究によれば、これらの大量絶滅のほとんどには一つの共通点がある。それは、火山溶岩と有毒ガスを数十万年、中には百万年という長期間にわたって噴出する大規模噴火の後に発生したということである。
白亜紀-古第三紀（K-Pg）絶滅と呼ばれる最も有名な大量絶滅は、カリブ海での彗星または小惑星の衝突に関連していたことは有名であるが、地質学者は、その衝突の前に、今日デカントラップとして知られている洪水玄武岩を残したインドでの長期にわたる噴火があったことを発見している。
＜関連情報＞
- https://news.berkeley.edu/2022/09/12/mega-eruptions-linked-to-most-mass-extinctions-over-past-500-million-years/
- https://www.pnas.org/doi/10.1073/pnas.2120441119
大陸性が古生代の絶滅を促進する Continental flood basalts drive Phanerozoic extinctions
Theodore Green , Paul R. Renne and C. Brenhin Keller
Proceedings of the National Academy of Sciences Published:September 12, 2022
DOI:https://doi.org/10.1073/pnas.2120441119
Significance
Although the causes of the five largest mass extinctions remain controversial, geochronological improvements have revealed an apparent correlation between large igneous provinces (LIPs) and periods of Phanerozoic faunal turnover. This paper establishes that this relationship is unlikely to occur by chance and defines an eruptive rate threshold, above which known continental LIPs correlate with large extinctions. Continental LIPs also have an approximately linear relationship between their eruptive rate and extinction magnitude. It is difficult to attribute the causality of any one extreme event like an extinction with certainty, but there is an overall correlation between continental LIPs and extinction events that warrants consideration.
Abstract
Refinements of the geological timescale driven by the increasing precision and accuracy of radiometric dating have revealed an apparent correlation between large igneous provinces (LIPs) and intervals of Phanerozoic faunal turnover that has been much discussed at a qualitative level. However, the extent to which such correlations are likely to occur by chance has yet to be quantitatively tested, and other kill mechanisms have been suggested for many mass extinctions. Here, we show that the degree of temporal correlation between continental LIPs and faunal turnover in the Phanerozoic is unlikely to occur by chance, suggesting a causal relationship linking extinctions and continental flood basalts. The relationship is stronger for LIPs with higher estimated eruptive rates and for stage boundaries with higher extinction magnitudes. This suggests LIP magma degassing as a primary kill mechanism for mass extinctions and other intervals of faunal turnover, which may be related to CO2, SO2, Cl, and F release. Our results suggest continental LIPs as a major, direct driver of extinctions throughout the Phanerozoic.
