科學家發現2億5000萬年前的滅絕事件是由西伯利亞火山爆發造成的證據
二疊紀大滅絕事件發生於大約2億5000萬年前。一組科學家團隊發現新證據顯示原因為現今西伯利亞地區發生大規模火山爆發，而導致嚴重的氣候變遷。
刊登於期刊《科學報告》(Scientific Reports)的這篇研究，發現在滅絕當時鎳元素的含量在全球都出現了高峰。異常多的鎳很有可能是來自同一時間在現今西伯利亞地區發生的大型火山噴發所釋放出來的噴氣(emanations)。研究人員表示噴發事件跟富含鎳的岩漿入侵體有關，這些由岩漿冷卻而形成的岩石含有某些地球上規模最大的鎳礦礦床。
研究人員利用感應耦合電漿質譜分析儀以原子層級測量稀有元素的豐度，結果證明二疊紀大滅絕事件時從南極到印度各地區都有出現鎳的異常高值，如此廣泛的分布顯示此現象在全世界都有出現。
從滅絕當時的鎳足跡得出的新證據，使科學家相信西伯利亞火山的劇烈活動造成嚴重全球暖化和其他環境變遷，使得超過90%的物種就此消失。
「西伯利亞的火山爆發，以及連帶發生大量進入地殼、富含鎳的岩漿入侵體，顯然將富含鎳的氣體釋放到大氣當中並散布至全球。」此篇論文的第一作者，紐約大學的地質學家Michael Rampino解釋。「於此同時，岩漿跟之前形成的煤炭礦床發生劇烈反應，釋放出二氧化碳和甲烷兩種溫室氣體。這可以解釋為什麼在大滅絕發生的時候，可以在海洋和陸地看到呈現強烈全球暖化的紀錄。海洋暖化使得它的流動變得相當遲緩，造成溶氧量降低，許多種類的海洋生物因而滅絕。」
「這項新發現給出進一步證據顯示地球經歷過的最嚴重滅絕事件，其導火線就是西伯利亞玄武岩噴發。此外，它對我們也有重大啟發。」此篇論文的共同作者，巴納德學院環境科學系的講師Sedelia Rodriguez表示，「我們期望將我們對於鎳和其他元素進行的研究範圍更加擴大，以精確描繪出此噴發事件的影響地區。我們冀望藉此可以更加瞭解噴發事件對陸上和海洋生物造成了何種影響而引發大滅絕。此外，我們也盼望這項研究可以幫助科學家確立未來是否有可能發生另一次此等規模的事件。」
Scientists Find Evidence that Siberian
Volcanic Eruptions Caused Extinction 250 Million Years Ago
A team of scientists has
found new evidence that the Great Permian Extinction, which occurred approximately
250 million years ago, was caused by massive volcanic eruptions that led to
significant environmental changes.
The study, which appears in the journal Scientific Reports,
reports a global spike in the chemical element nickel at the time of extinction.
The anomalous nickel most likely came from emanations related to the concurrent
huge volcanic eruptions in what is now Siberia. These eruptions, the
researchers say, are associated with nickel-rich magmatic intrusions—rocks
formed from the cooling of magma—that contain some of the greatest deposits of
nickel ore on the planet.
Using an Inductively
Coupled Plasma Mass Spectrometer, which measures the abundance of rare elements
at their atomic level, the scientists documented anomalous peaks of nickel in
regions ranging from the Arctic to India at the time of the Great Permian
Extinction—distributions that suggest these nickel anomalies were a worldwide
phenomenon.
This new evidence of
a nickel fingerprint at the time of the extinctions convinced the scientists
that it was the volcanic upheaval in Siberia that produced intense global
warming and other environmental changes that led to the disappearance of more
than 90 percent of all species.
“The Siberian
volcanic eruptions and related massive intrusions of nickel-rich magmas into
the Earth’s crust apparently emitted nickel-rich volatiles into the atmosphere,
where they were distributed globally,” explains New York University geologist
Michael Rampino, the paper’s senior author. “At the same time, explosive
interactions of the magma with older coal deposits could have released large
amounts of carbon dioxide and methane, two greenhouse gases, which would
explain the intense global warming recorded in the oceans and on land at the
time of the mass extinctions. The warm oceans also became sluggish and depleted
in dissolved oxygen, contributing to the extinction of many forms of life in
the sea”.
“This new finding,
which contributes further evidence that the Siberian Trap eruptions were the
catalyst for the most extensive extinction event Earth has ever endured, has
exciting implications,” says Sedelia Rodriguez, a co-author of the paper and
lecturer in the department of Environmental Science at Barnard College. “We
look forward to expanding our research on nickel and other elements to
delineate the specific areas affected by this eruption. In doing so, we hope to
learn more about how these events trigger massive extinctions that affect both
land and marine animals. Additionally, we hope this research will contribute to
determining whether an event of this magnitude is possible in the future.”
原始論文；Michael
R. Rampino, Sedelia Rodriguez, Eva Baransky, Yue Cai. Global nickel
anomaly links Siberian Traps eruptions and the latest Permian mass extinction. Scientific
Reports, 2017; 7 (1) DOI: 10.1038/s41598-017-12759-9
引用自：New York University. "Siberian volcanic
eruptions caused extinction 250 million years ago, new evidence shows."
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