Most major geological events in Earth's recent history have clustered in 27.5-million-year intervals — a pattern that scientists call the "pulse of the Earth."
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00:00Did you know that the Earth has a pulse? A geological pulse, that is.
00:06Most major geological events in Earth's recent history have clustered in 27.5 million year intervals,
00:13a pattern that scientists are now calling the Pulse of the Earth.
00:18Over the past 260 million years, dozens of major geological events,
00:22from sea-level changes to volcanic eruptions, seem to follow this rhythmic pattern.
00:28The authors say that geologists have wondered for a really long time
00:32whether there's a certain cycle of around 30 million years in the geological record.
00:37But until recently, poor dating of such events made the phenomenon really difficult to study quantitatively.
00:44In a new study, the researchers conducted a quantitative analysis
00:48to see if these events were random or if there was an underlying pattern to them.
00:54To do this, they first searched the literature and found 89 major geological events
00:59that occurred in the past 260 million years.
01:02These included extinctions, ocean anoxic events,
01:07or times when the oceans were toxic due to oxygen depletion,
01:11sea-level fluctuations, major volcanic activity called flood basalt eruptions,
01:17and changes in the organization of Earth's tectonic plates.
01:22Then, the researchers put the events in chronological order
01:25and used a mathematical tool known as Fourier analysis
01:28to pick up spikes in the frequency of events.
01:32They discovered that most of these events clustered into 10 separate times
01:36that were, on average, 27.5 million years apart.
01:42Though that number may not be exact, it's probably a pretty good estimate, the researchers say.
01:48However, they only looked at the past 260 million years
01:52when the dating of such events is most accurate.
01:55Still, they think the results likely extend further back in our planet's history.
02:01It's not clear what's causing such a pulse in geological activity,
02:04but the researchers have several hypotheses.
02:08It could be internally driven by plate tectonics and movement inside the mantle,
02:12or it could have something to do with the movement of Earth in the solar system in the galaxy.
02:18The researchers hope to get even better data on the dating of certain geological events
02:23and plan to analyze a longer time period to see if the pulse extends further back in time.
02:29They also hope that if, one day, they can get better numbers on the astronomical movements
02:34of Earth through the solar system in the Milky Way,
02:37they can see if there is any correlation in the astronomical and geological cycles.
02:42In any case, if such a pattern exists, the last cluster was about 7 million to 10 million years ago,
02:49so the next one would likely come in 10 million to 15 million years.
03:07NASA Jet Propulsion Laboratory, California Institute of Technology