Geologists have been investigating a potential cycle in geological events for a long time. A recent analysis on the ages of 89 well-understood geological events from the past 260 million years show a catastrophic 27.5 million year pulse in eight clusters of world-changing geologic events over geologically small timespans.

This pulse of clustered geological events – including volcanic activity, mass extinctions, plate reorganizations, and sea level rises – is incredibly slow, a 27.5-million-year cycle of catastrophic ebbs and flows.

These events include times of marine and non-marine extinctions, major ocean-anoxic events, continental flood-basalt eruptions, sea-level fluctuations, global pulses of intraplate magmatism, and times of changes in seafloor-spreading rates and plate reorganizations.

These cyclic pulses of tectonics and climate change may be the result of geophysical processes related to the dynamics of plate tectonics and mantle plumes, or might alternatively be paced by astronomical cycles associated with the Earth’s motions in the Solar System and the Galaxy.

Exactly why these cycles occur remains unknown, but there are some interesting theories.

Our hearts beat at a resting rate of 60 to 100 beats per minute. Lots of other things pulse, too. The colors we see and the pitches we hear, for example, are due to the different wave frequencies (“pulses”) of light and sound waves.

Now, a study in the journal Geoscience Frontiers finds that Earth itself has a pulse, with one “beat” every 27.5 million years. That’s the rate at which major geological events have been occurring as far back as geologists can tell.

According to lead author and geologist Michael Rampino of New York University’s Department of Biology, “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 new study is not the first time that there’s been a suggestion of a planetary geologic cycle, but it’s only with recent refinements in radioisotopic dating techniques that there’s evidence supporting the theory. The authors of the study collected the latest, best dating for 89 known geologic events over the last 260 million years:

The dates provided the scientists a new timetable of Earth’s geologic history.

Putting all the events together, the scientists performed a series of statistical analyses that revealed that events tend to cluster around 10 different dates, with peak activity occurring every 27.5 million years. Between the ten busy periods, the number of events dropped sharply, approaching zero.

Perhaps the most fascinating question that remains unanswered for now is exactly why this is happening. The authors of the study suggest two possibilities:

“The correlations and cyclicity seen in the geologic episodes may be entirely a function of global internal Earth dynamics affecting global tectonics and climate, but similar cycles in the Earth’s orbit in the Solar System and in the Galaxy might be pacing these events.

Whatever the origins of these cyclical episodes, their occurrences support the case for a largely periodic, coordinated, and intermittently catastrophic geologic record, which is quite different from the views held by most geologists.”

Assuming the researchers’ calculations are at least roughly correct — the authors note that different statistical formulas may result in further refinement of their conclusions — there’s no need to worry that we’re about to be thumped by another planetary heartbeat. Luckily for us, the research suggests we have another 20 million years before the next ‘pulse’

Catastrophic events on Earth don’t come at random, but are dictated by a ‘pulse’ of geologic activity that occurs every 27.5 million years, a new study reveals.