This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: Earth's poles do not always stay in the same place. For example, a region once near the North Pole can end up near the equator, and an area near the equator can shift up toward the pole.
This is known as true polar wander (TPW), and it's when Earth's crust and mantle shift together relative to its spin axis. Some scientists believe it is negligible or persistently slow. But a new study suggests that rapid polar wander happened several times during the last 320 million years, especially between 150 and 140 million years ago and between 100 and 90 million years ago.
When research teams want answers about true polar wander, they usually look at ancient magnetic fields locked inside rocks. But a small team led by Mathew Domeier at the University of Oslo in Norway took a different approach. They analyzed ancient sea levels, as they detail in a paper published in Science.
The reason is that when Earth shifts during a polar wander event, the oceans respond immediately. Water rises in some areas and falls in others, which leaves traceable signatures in ancient flooding records across the continents. The scientists used digital reconstruction maps of global continental flooding.
These document where land was exposed and flooded over the last 320 million years, divided into 10-million-year snapshots. They compared consecutive maps to track where the seas advanced and retreated across each continent. Next, the researchers used computer models to look for a specific pattern.
When Earth's solid outer layers shift relative to its spin axis, the oceans respond faster than the solid Earth can change shape. This causes relative sea levels to rise in two opposite regions and fall in two others. Finding that distinct high-and-low pattern across the ancient maps would help confirm that rapid true polar wander really happened.
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