A new study finds evidence that Earth may have undergone several episodes of rapid true polar shift over the past 320 million years, with the strongest signals in the Jurassic and Cretaceous. Instead of relying primarily on ancient magnetic fields, the researchers tracked patterns of continental flooding and retreats caused when the solid Earth shifted relative to its spin axis. The results support rapid events between about 150 and 140 million years ago and 100 and 90 million years ago, while challenging the idea that true polar drift has always been negligible or persistently slow. Earth’s geographic poles may appear permanent on human time scales, but the planet’s solid exterior has not always remained fixed relative to its axis of rotation. A new study suggests that the crust and mantle underwent several episodes of relatively rapid reorientation over the past 320 million years. Instead of relying primarily on magnetic signatures preserved in rocks, the researchers found evidence in an unexpected archive: ancient changes in where oceans flooded continents. The study, led by Mathew Domeier at the University of Oslo and published in Science, identified four intervals with statistically significant signals consistent with a true fast polar shift. The evidence was strongest about 150 and 140 million years ago and again between 100 and 90 million years ago. The findings add an independent line of evidence to a long-running debate about whether the Earth sometimes reorients itself in sudden geological explosions rather than just through slow, continuous changes. (A) Cross section of the Earth (with exaggerated oblate shape) showing the displacement of the transient equatorial bulge of the solid Earth (with respect to the reference geoid) during a TPW Event. (B) Normalized response of the spherical harmonic of degree 2 and order 1 (Y₂₁); Nodal planes are highlighted in black. (CREDIT: Mathew Domeier et al, Science 2026) The planet can rebalance itself. True polar shift does not mean that Earth’s magnetic poles simply move, nor does it describe continents moving independently through plate tectonics. Instead, the crust and mantle rotate together relative to the planet’s spin axis. The core and broad climate belts remain tied to that axis of rotation as the solid exterior moves beneath them. The process can occur because the Earth is not a perfect sphere. The rotation creates an equatorial bulge and the planet tends to organize its internal mass so that its greatest moment of inertia remains aligned with the axis of spin. Mantle convection, subsidence of tectonic slabs, and other processes redistribute mass. If that distribution becomes sufficiently unbalanced, the solid Earth can reorient itself. Detecting such movements in deep time is difficult because normal plate tectonics can create very similar signals. Sea levels offer a different record. Most reconstructions of the true polar shift depend on paleomagnetism. Magnetic minerals can preserve the direction of Earth’s ancient magnetic field, allowing scientists to estimate where a continent once was relative to the poles. Estimated contributions of true polar shift (TPW) to sea level change over the past 320 million years. The analysis identifies four intervals with significant TPW effects and estimates their contributions relative to global sea level changes. (CREDIT: Mathew Domeier et al, Science 2026) But interpreting that data requires separating the reorientation of the entire Earth from the ordinary movement of tectonic plates. Hot spot reference frames can help, but hot spots themselves move and reliable traces become scarce as geological history progresses. Domeier and his colleagues, instead, turned to sea level. When true polar shift begins, the solid Earth moves relative to its rotational bulge. The oceans can respond almost immediately, while the mantle and lithosphere take longer to remodel. That mismatch creates a distinctive global pattern. Some continental regions experience relative sea level rise and flooding, while other regions experience sea level fall and exposure. The expected pattern has four wide lobes, with two regions gaining water and two losing it. The researchers reconstructed 320 million years. The team analyzed global maps that recorded which continental areas were submerged or exposed at intervals of 10 million years. Estimates of true polar drift (TPW) over the past 320 million years compare its speed, direction, and rotation using plate motion models. paleomagnetic data and reference frames. Reconstructions map these changes against the best-fitting TPW axis. (CREDIT: Mathew Domeier et al, Science 2026) By comparing one map to the next, they identified places where seas advanced across continents and places where water receded. They then used logistic regression to test whether those flooding patterns matched the geometry expected from a true polar shift. Importantly, the method looks for the spatial pattern rather than relying on the absolute amount of sea level change. The technique does not directly calculate exactly how fast the Earth moved. However, based on previous physical models, the patterns visible at the 10-million-year resolution of the maps would generally require actual polar shift rates of at least about 0.6 degrees per million years. Therefore, the researchers classified the detected events as rapid on geological time scales. Two intervals produced particularly strong evidence. Four intervals crossed the statistical threshold of the study: 200 to 190 million years ago, 150 to 140 million years ago, 100 to 90 million years ago. and 30 to 20 million years ago. Not all four were equally convincing. The strongest signal appeared between 150 and 140 million years ago, spanning the Late Jurassic and Early Cretaceous. The flooding pattern showed sea level rise in parts of South America, Antarctica and eastern Asia, while southwestern North America, western Europe and eastern Australia experienced receding seas. The researchers reconstructed a clockwise reorientation around an axis near 58 degrees east longitude. That interval coincides closely with independent studies that have proposed a major episode of true Jurassic polar shift from paleomagnetic measurements and plate reconstructions. The second strong result occurred between 100 and 90 million years ago. South America, Western and Southern Africa, and East Asia experienced widespread regression, while much of North America and Europe experienced transgression. The best-fitting model indicated rotation in the opposite direction around an axis close to 53 degrees east. Other episodes remain less certain. The Early Jurassic signal between 200 and 190 million years ago was statistically significant, but only marginally. Its fit to the observed flooding pattern was comparatively poor, leading researchers to treat it with caution. A possible event that occurred between 30 and 20 million years ago was also weaker than the two main Mesozoic examples. For most of the Cenozoic, the analysis found little evidence for true rapid polar shift detectable at this temporal resolution. motion. The debate is far from resolved. The true polar shift remains controversial because different reconstruction techniques can produce different stories. A 2025 study in AGU Advances, for example, reconstructed a large but generally slow true polar shift over the past 320 million years and found no evidence for previously proposed rapid Cretaceous and Late Jurassic oscillations. Other paleomagnetic studies have reported much faster movements. A 2024 Nature Communications paper reconstructed a shift of about 12 degrees southward quickly followed by about 10 degrees of movement northward around the Jurassic-Cretaceous transition. The new sea level approach is important because it is based on a largely independent geological signal. The agreement between flood patterns and some paleomagnetic reconstructions makes the strongest Mesozoic episodes more difficult to rule out as artifacts of a single technique. If true rapid polar drift occurred repeatedly, the consequences would go far beyond geography. Continents could move rapidly through climate belts, altering precipitation, temperature, marine environments and habitats without requiring equivalent changes in atmospheric greenhouse gases. Earth’s poles may appear stable today, but the geological record increasingly suggests that the solid planet beneath them has sometimes been much more restless. Dig deeper into the true polar shift These recent studies explore competing reconstructions of the true polar shift and its potential effects on climate and the environment. A true Late Cretaceous polar shift oscillation: High-resolution Italian paleomagnetic records provided evidence for a true polar oscillation of about 12 degrees between about 86 and 78 million years ago. (Nature Communications, 2021) The research results are available online in the journal Science.Related Stories
