[Rockhounds] Earth has a 'pulse' of 27.5 million years

[Kreigh Tomaszewski]

Most major geological events in Earth's recent history have clustered in
27.5-million-year intervals — a pattern that scientists are now calling the
"pulse of the *Earth* <https://www.livescience.com/earth.html>," according
to a new study.

Over the past 260 million years, dozens of major geological events, from
sea level changes to *volcanic eruptions*
<https://www.livescience.com/27295-volcanoes.html>, seem to follow this
rhythmic pattern.

"For quite a long time, some geologists have wondered whether there's a
cycle of around 30 million years in the geologic record," said lead author
Michael Rampino, a professor in the departments of biology and
environmental studies at New York University. But until recently, poor
dating of such events made the phenomenon difficult to study quantitatively.

"Many, but maybe even most, [geologists] would say that geological events
are largely random," Rampino told Live Science. In the new study, Rampino
and his team conducted a quantitative study to see if they were indeed
random or if there was an underlying pattern.

The team first scoured the literature and found 89 major geological events
that occurred in the past 260 million years. These included extinctions,
ocean anoxic events (times when the oceans were toxic due to oxygen
depletion), sea level fluctuations, major volcanic activity called
flood-basalt eruptions and changes in the organization of Earth's *tectonic
plates* <https://www.livescience.com/37706-what-is-plate-tectonics.html>.

Then, the researchers put the events in chronological order and used a
mathematical tool known as Fourier analysis to pick up spikes in the
frequency of events. They discovered that most of these events clustered
into 10 separate times that were, on average, 27.5 million years apart.
That number may not be "exact," but it's a "pretty good estimate" with a
96% confidence interval, meaning it's "unlikely to be a coincidence,"
Rampino said.

https://www.livescience.com/pulse-of-the-earth.html