Mass extinctions. Massive volcanic eruptions. Oceans suddenly stripped of oxygen. At first glance, Earth’s greatest geological catastrophes seem to have little in common, save for their sheer scale.
However, for decades, scientists have wondered whether these seemingly unrelated events might actually follow a hidden rhythm rooted hundreds of millions of years in the past.
The possibility that Earth’s geological history follows a long-term rhythm has been a subject of debate for decades. This idea dates back to research published in the 1980s, when scientists first proposed that mass extinctions and other major geological events might recur at regular intervals. Earlier studies had identified similar periodic patterns, yet the concept remains controversial.
Now, a study published in the journal Evolving Earth revisits this evidence using updated geological timescales and statistical methods.
The analysis indicates that evidence for a geological cycle lasting approximately 27.5 million years continues to mount, suggesting that many of Earth’s most significant upheavals may be linked by long-term processes rather than being isolated catastrophes.
Drawing on previously published geological data, New York University geologist Michael Rampino re-examined 89 major geological events from the last 260 million years, employing updated geological age data and statistical analysis. The dataset includes information on marine mass extinctions, oceanic anoxic events, continental flood basalt eruptions, sea-level fluctuations, terrestrial tetrapod extinctions, changes in seafloor spreading rates, and pulses of intraplate volcanism.
Collectively, these data point to a dominant periodicity of approximately 27.5 million years, as well as a weaker cycle lasting about 8.9 million years.
Rather than asserting that one geological catastrophe directly triggers another, the new analysis suggests that multiple Earth systems may periodically respond to the same underlying processes unfolding over tens of millions of years.
The exact nature of these processes remains unclear.
The analysis also examines potential drivers of this long-term rhythm.
One possibility lies deep within the Earth itself.
The planet’s mantle is in constant convective motion, albeit at an incredibly slow pace. Periodic changes in mantle convection or the formation of mantle plumes can influence volcanic activity, plate tectonics, mountain building, and other large-scale geological processes.
Because these systems are closely interconnected, disturbances originating deep within the Earth can ultimately propagate to the planet’s surface, oceans, climate, and biosphere.
Another hypothesis focuses on the interaction between the Earth’s surface and its internal structures. Long-term orbital variations influence climate and sea levels by periodically redistributing vast quantities of water, ice, and sediment across the planet. Rampino discusses the possibility that these changing surface loads subtly alter stresses within the Earth’s crust and upper mantle, potentially influencing tectonic and volcanic activity over geological timescales.
Rampino also considers potential influences originating from outside Earth—an idea he has been exploring since the 1980s.
As the Solar System orbits the center of the Milky Way, it oscillates above and below the galactic mid-plane; the timing of these crossings coincides with periods of major geological upheaval. Other researchers suggest that these crossings could also gravitationally disturb comets in the distant Oort cloud, increasing the likelihood of collisions with large asteroids.
Another, even more speculative hypothesis suggests that if dark matter is concentrated near the galactic plane, some of it might occasionally be captured by Earth.
Over millions of years, this process could generate a small amount of internal heat, potentially influencing geological activity. However, there is currently no direct evidence to support any of these mechanisms, so they remain highly controversial.
Major asteroid impacts are addressed separately in the paper. Although they were not included in the statistical analysis of the 89 geological events, the timing of several of Earth’s largest known impact craters generally aligns with the proposed 27.5-million-year cycle, as Rampino has discussed in previous work.
Rampino suggests that this pe…warrants further investigation, though he stops short of asserting a direct causal link. The question remains as to whether the observed cycle reflects a genuine feature of Earth’s history.
Identifying periodic patterns spanning hundreds of millions of years is inherently challenging.
Geological data are incomplete, the dating of ancient events becomes increasingly uncertain the further back one looks, and statistical analysis can sometimes reveal apparent cycles that vanish as more evidence accumulates.
Rather than claiming the debate is settled, Rampino concludes that the proposed 27.5-million-year periodicity persists, despite decades of increasingly precise geological timescales and expanding datasets.
However, because this idea challenges long-held interpretations of the geological record, it is likely to remain a subject of debate.
Yet, if this pattern is confirmed by future research, Earth’s major geological upheavals might prove to be more than just isolated catastrophes scattered across the ages.
Instead, they may reflect recurring manifestations of long-term processes that have shaped our planet over hundreds of millions of years.
“While these ideas largely lie outside mainstream geological thinking,” Rampino concludes, “they could represent the first steps toward a major conceptual breakthrough in the Earth sciences—one that recognizes the global correlation of major geological events, the generally periodic nature of the multi-million-year geological record, and the astronomical connections that could more firmly place our planet within its true cosmic context.”
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