原文網址：https://www.nyu.edu/about/news-publications/news/2021/june/earth-pulse.html
分析2億6000萬年來的大型地質事件發現每隔2750萬年就會密集發生
圖片來源：紐約大學
根據發表在期刊《地科前沿》(Geoscience Frontiers)的新研究，地球的地質活動似乎有2750萬年的週期，使得地球就像是有脈搏一樣。
「許多地質學家相信地質事件的發生時間是隨機的。但是我們的研究提出的統計證據顯示地質事件存在著一個共同的週期，代表它們之間具有相關性，而非全然隨機，」本研究的主要作者，紐約大學生物學系的地質學家Michael
Rampino教授表示。
研究人員在過去50年曾數次提出大型地質事件，包括火山活動與發生在陸地或海洋的大滅絕事件會有規律地出現，週期大概從2600萬年到3600萬年不等。但是過往比對地質紀錄的研究受阻於地質事件的定年有其限制，使得科學家難以進行定量化的研究。
然而，隨著放射性同位素定年法大幅改進以及地質年代表的更動，研究人員對於過去事件的發生時間也有了新的數據。Rampino和同僚彙整他們可以得到的最新定年數據，更新了過去2600萬年的大型地質事件紀錄並且加以分析。
團隊分析了過去2600萬年之內，89件經過良好定年的大型地質事件的發生年代。這些事件包括海洋或陸上的大滅絕事件、稱作洪流玄武岩的大量岩漿噴發、海洋缺氧、海平面變化以及地球板塊運動的變化或是重組。
他們發現過去2600萬年這些全球性的地質事件總體來說集中在10個不同的時間點，大約相隔2750萬年就會聚集成一道高峰。最近一次地質事件密集發生的時間大約在700萬年前，代表下次大型地質事件集體發生的時間還要再過2000萬年以上。
研究人員推測這些脈動或許是地球內部週期性的活動所造成，也就是跟板塊運動的動力來源以及氣候有關的地球物理作用。不過，地球在太空中的運行軌道的類似週期，也有可能會決定這些事件的步調。
「不管這些週期性事件的起源為何，我們的發現支持了地質紀錄大體來說具有週期，這些事件之間有所連動而間歇地造成災難。這違背了許多地質學家持有的觀點，」Rampino解釋。
研究作者除了Rampino之外，還有紐約大學資料科學中心的Yuhong
Zhu，以及卡內基科學研究院的Ken
Caldeira。
The Earth has a pulse—a
27.5-million-year cycle of geological activity
Analysis of 260
million years of major geological events finds recurring clusters 27.5 million
years apart
Geologic activity on Earth appears to
follow a 27.5-million-year cycle, giving the planet a “pulse,” according to a
new study published in the journal Geoscience
Frontiers.
“Many geologists believe that geological events are
random over time. But our study provides statistical evidence for a common
cycle, suggesting that these geologic events are correlated and not random,”
said Michael Rampino, a geologist and professor in New York University’s
Department of Biology, as well as the study’s lead author.
Over the past five decades, researchers have proposed
cycles of major geological events—including volcanic activity and mass
extinctions on land and sea—ranging from roughly 26 to 36 million years. But
early work on these correlations in the geological record was hampered by
limitations in the age-dating of geologic events, which prevented scientists
from conducting quantitative investigations.
However, there have been significant improvements in
radio-isotopic dating techniques and changes in the geologic timescale, leading
to new data on the timing of past events. Using the latest age-dating data
available, Rampino and his colleagues compiled updated records of major
geological events over the last 260 million years and conducted new analyses.
The team analyzed the ages of 89 well-dated major
geological events of the last 260 million years. These events include marine
and land extinctions, major volcanic outpourings of lava called flood-basalt
eruptions, events when oceans were depleted of oxygen, sea-level fluctuations,
and changes or reorganization in the Earth’s tectonic plates.
They found that these global geologic events are
generally clustered at 10 different timepoints over the 260 million years,
grouped in peaks or pulses of roughly 27.5 million years apart. The most recent
cluster of geological events was approximately 7 million years ago, suggesting
that the next pulse of major geological activity is more than 20 million years
in the future.
The researchers posit that these pulses may be a
function of cycles of activity in the Earth's interior—geophysical processes
related to the dynamics of plate tectonics and climate. However, similar cycles
in the Earth’s orbit in space might also be pacing these events.
“Whatever the origins of these cyclical episodes, our
findings support the case for a largely periodic, coordinated, and
intermittently catastrophic geologic record, which is a departure from the
views held by many geologists,” explained Rampino.
In addition to Rampino, study authors include Yuhong
Zhu of NYU’s Center for Data Science and Ken Caldeira of the Carnegie
Institution for Science.
原始論文：Michael R.
Rampino, Ken Caldeira, Yuhong Zhu. A pulse of the Earth: A 27.5-Myr
underlying cycle in coordinated geological events over the last 260 Myr. Geoscience
Frontiers, 2021; 12 (6): 101245 DOI: 10.1016/j.gsf.2021.101245
引用自：New York University. "The Earth has a pulse -- a
27.5-million-year cycle of geological activity.”
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