"Geological time scales may look like tidy timelines in textbooks, but their boundaries tell a much more chaotic story. Our findings show that what seemed like uneven noise is actually a key to understanding how our planet changes, and how far that change can go," says Prof. Spiridonov, geologist and paleontologist.
The research team included Prof. Shaun Lovejoy and Rhisiart Davies of McGill University (Canada), Assoc. Prof. Fabrice Lambert of the Pontifical Catholic University of Chile, Raphael Hebert of the Alfred Wegener Institute (Germany), and Prof. Spiridonov from VU (Lithuania). Their analysis examined the placement of boundaries marking epochs, periods, and eras across the official International Geochronological Chart and biozone-based scales defined by extinct species such as conodonts, graptolites, and ammonoids.
Across all scales, from local to global, the team discovered that time boundaries cluster instead of being evenly spaced. These clusters, separated by long periods of relative stability, were shown to follow multifractal patterns - mathematical structures that repeat across different scales.
"The intervals between key events in Earth's history, from mass extinctions to evolutionary explosions, are not scattered completely evenly. They follow a multifractal logic that reveals how variability cascades through time," explains Prof. Spiridonov.
This finding allowed the team to calculate Earth's 'outer time scale' - the duration needed to capture the system's full variability. The estimate indicates that the limit is roughly 500 million years or more. "If we want to understand the full range of Earth's behaviours, whether periods of calm or sudden global upheaval, we need geological records that cover at least half a billion years. And ideally, a billion," Spiridonov adds.
The authors argue that this helps clarify why short-term records cannot capture the extremes of planetary evolution. To describe this structure, they introduced the Compound Multifractal-Poisson Process, a model showing how events are nested within one another, with clusters embedded in clusters, all controlled by a single statistical process.
"We now have mathematical evidence that Earth system changes are not just irregular. They are deeply structured and hierarchical. This has huge implications not only for understanding Earth's past but also for how we model future planetary change," concludes Spiridonov.
Research Report:From eons to epochs: multifractal geological time and the compound multifractal - Poisson process
Related Links
Vilnius University (VU) Faculty of Chemistry and Geosciences
Explore The Early Earth at TerraDaily.com
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