A Norwegian study reveals rapid shifts in Earth's rocky envelope over 320 million years, with three during the dinosaur era, challenging past climate reconstructions.
Rapid pole shifts identified in Earth's history
A Norwegian research team has identified four instances of rapid shifts in the Earth's rocky envelope over the past 320 million years, with three of these occurring during the dinosaur era. The study, published in Science, suggests these shifts happened much faster than previously thought, with the current drift of the poles reaching ten centimeters per year.Pole drift faster than tectonic plates
The entire rocky envelope of the Earth tilts relative to its axis of rotation, and geophysicists from the University of Oslo showed that this phenomenon experienced sudden accelerations in the past. These episodes may require revising the reconstructed climates of the dinosaur era, as they could have significantly affected global weather patterns.New method to detect pole shifts
Until now, geophysicists relied on the magnetic signature of rocks to detect these tilts, but results remained contradictory. The movement of tectonic plates could be confused with a tilt of the entire envelope. The Norwegian team identified another indicator, the level of the seas, which provided clearer evidence of these shifts.Sea level patterns reveal pole drift
Researchers compared paleogeographic maps tracing 320 million years, cut into slices of ten million years. The reasoning is based on the shape of the planet, slightly bulging at the equator. When the rocky envelope tilts, this water bulge remains in place and the continents slide under it. Two opposite quadrants of the globe become flooded, while the other two dry out. This pattern of four zones betrays each episode of pole drift.Timeline of pole shifts
The pattern appears four times in the data. According to the study published in Science, the oldest dates back to the Lower Jurassic, between 200 and 190 million years. Two others mark the transition between Jurassic and Cretaceous, around 150 to 140 million years, then the middle of the Cretaceous, between 100 and 90 million years. The most recent event is not specified in the report.
