Study finds major geological events occur in 27.5-million-year cycle

A new study reveals that Earth's most catastrophic events, including mass extinctions and massive volcanic eruptions, have followed a cyclical pattern occurring roughly every 27 million years. Researchers from the University of Sydney and the University of the Sorbonne analyzed geological records spanning the past 260 million years, identifying 10 clusters of major disasters that align with this long-term cycle.

The pattern affects the entire planet, with each cluster bringing a surge of devastating events such as asteroid impacts, volcanic flood basalt eruptions, and mass die-offs of species. The most recent cluster occurred about 7 million years ago, suggesting the next one may not arrive for another 20 million years. However, the study's lead author, Professor Michael Rampino, notes that the cycle is not perfectly regular, with intervals varying by a few million years.

This discovery matters because it provides a new framework for understanding Earth's geological history and the forces that shape life on our planet. The researchers propose that the cycle may be driven by the solar system's movement through the Milky Way, which periodically increases the likelihood of comet impacts. The study, published in the journal Historical Biology, builds on earlier work that suggested a 27-million-year cycle in extinction events, but this new analysis expands the evidence to include other major disasters.

Specific data from the study shows that the 10 identified clusters include the Permian-Triassic extinction (about 252 million years ago), which wiped out 96% of marine species, and the Cretaceous-Paleogene extinction (66 million years ago) that killed the dinosaurs. The researchers also note that the cycle aligns with known episodes of flood basalt volcanism, such as the Siberian Traps and the Deccan Traps.

Background research has long debated whether Earth's catastrophes occur randomly or in cycles. This study strengthens the case for a cyclical pattern, possibly linked to the solar system's orbit around the galactic center, which takes about 250 million years. The team suggests that gravitational perturbations from the galaxy's spiral arms could dislodge comets from the Oort Cloud, sending them toward Earth.

Looking ahead, the researchers emphasize that while the next major cluster is millions of years away, understanding this cycle could help refine models of Earth's past and future. They call for further investigation into the astronomical mechanisms behind the pattern, which may also offer insights into the potential for future catastrophic events.