Disastrous events including volcanic eruptions and mass extinctions seem to occur regularly – dictated by a “pulse” that beats every 27.5 million years, a new study found.
Researchers used improved radio-isotope dating technology to precisely pinpoint disasters including sea level rises and volcanic outbursts.
They found that such events are “not random” and appear to be linked to a recurring cycle of major geological events.
The last cycle was 7 million years ago, meaning it should be another 20 million years until another round of such events.
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Michael Rampino, a geologist and professor in New York University's Department of Biology, said, "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.”
The research was published in the journal Geoscience Frontiers.
Researchers have previously proposed cycles of major geological events – including volcanic activity and mass extinctions on land and sea – that range from roughly 26 to 36 million years.
But it’s been hard to accurately date many events.
In recent years, 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.
Rampino and his colleagues analysed 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 reorganisations 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 researchers believe 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.
Alternatively, similar cycles in the Earth's orbit in space might also be pacing these events.
Rampino said: "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.”
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