La Terre pourrait-elle avoir un rythme caché de catastrophes ?

New research suggests Earth might follow a hidden cycle of catastrophic events spanning tens of millions of years. Scientists have long debated whether seemingly unrelated phenomena, mass extinctions, massive volcanic eruptions, and oceans suddenly deprived of oxygen, could be linked through a recurring pattern. A new analysis published in Evolving Earth strengthens the case for such a rhythm, pointing to evidence of a geological cycle approximately 27.5 million years in duration. The idea of a long-term rhythm in Earth's history dates back to the 1980s, when early studies hinted at possible regular intervals for mass extinctions and other major geological events. While subsequent research has noted similar patterns, the concept remained controversial due to conflicting interpretations and limited data. The latest study, led by geologist Michael Rampino from New York University, revisits these findings using modern geological time scales and updated statistical methods. His analysis draws on 89 key geological events over the past 260 million years, including marine mass extinctions, periods of oceanic anoxia, continental basalt eruptions, sea level changes, land vertebrate extinctions, variations in seafloor spreading rates, and waves of volcanic activity. Rampino’s dataset reveals a dominant periodicity of roughly 27.5 million years, with a weaker secondary cycle of around 8.9 million years. These cycles suggest that many of Earth’s most dramatic upheavals may not be isolated incidents but part of interconnected, long-term processes. However, the study does not claim one geological catastrophe directly causes another. Instead, it proposes that multiple systems within Earth periodically respond to underlying processes that span tens of millions of years, though these mechanisms remain poorly understood. One potential driver of this rhythm lies deep within the planet. Earth's mantle continuously moves, albeit extremely slowly. Periodic changes in this movement or the occurrence of so-called mantle plumes could influence volcanism, plate tectonics, and other geological processes. Since these systems are interconnected, disturbances originating deep within the Earth could eventually manifest on the surface, affecting oceans, climate, and the biosphere. Another hypothesis focuses on interactions between Earth's surface and its interior. Long-term changes in Earth's orbital path affect climate and sea levels, leading to shifts in the distribution of vast masses of water, ice, and sediment. Rampino argues that these load changes on the surface could subtly alter stresses in the crust and upper mantle, thereby influencing tectonic and volcanic activity. The study also considers external influences beyond Earth. Since the solar system orbits the center of the Milky Way galaxy, it periodically moves above and below the galactic plane. The timing of these crossings aligns with some of Earth's largest geological upheavals. Some researchers speculate that these movements could gravitationally perturb comet trajectories in the distant Oort Cloud, increasing the likelihood of impacts by large extraterrestrial bodies. An even more speculative idea suggests that Earth might occasionally attract particles of dark matter concentrated near the galactic plane. Over millions of years, this process could generate internal heat, potentially influencing geological activity. However, there is currently no direct evidence supporting any of these mechanisms. The study separately examines impacts from large asteroids. Although these were not included in the statistical analysis of 89 geological events, the timing of several of the largest known impact craters appears to coincide with the proposed 27.5-million-year cycle. Rampino notes that this coincidence warrants further investigation. The research underscores the complexity of Earth's geological history and highlights the need for continued exploration into the forces shaping our planet. As scientists refine their understanding of these cycles, they may uncover deeper connections between Earth's internal dynamics and the broader cosmic environment.