Researchers from the University of Oslo’s Centre for Planetary Habitability have found compelling new evidence that the Earth underwent several episodes of rapidly shifting poles after the land masses moved, which scientists call “true polar wander,” during the Jurassic and Cretaceous periods.
The research team behind the findings said their work refutes a longstanding view that TPW was negligible or persistently slow, and challenges researchers to consider TPW as an “episodic control on sea level change and likely other global environmental and biological dynamics.”
The Controversy Behind Earth’s Shifting Poles
Earth is not a perfect sphere, so it depends on an even distribution of mass to maintain balance. Several phenomena can cause Earth’s land masses to move or even change position, including continental drift and other tectonic and mantle-related processes. This redistribution reorients Earth’s spin, or TPW.
According to a statement announcing the findings, Earth’s crust and mantle “effectively shift” relative to the planet’s spin axis. However, its core and climate belts remain tied to the axis.
The Oslo research team said if TPWs occurred more rapidly than previously assumed, they would produce major climate changes, altering the Earth’s biosphere and magnetic field. But evidence for rapid TPWs has proved elusive, since normal tectonic motion can give researchers a false positive.
“Paleomagnetic evidence has been used to propose fast episodes of TPW, but limitations of the paleomagnetic record have precluded definitive results,” they explained.
An editorial summary of the research agreed, noting that it is “difficult to detect with standard approaches using paleomagnetic measurements.”
Patterns Were Consistent with Rapid TPW Over the Past 320 Million Years
While previous studies have provided contradictory results, the team noted that TPW is “presently occurring at a rate of ~10 centimeters per year, exceeding the mean rate of differential plate motion.”
“Whether this rate is transient and negligible on geological timescales or whether Earth has experienced rapid TPW lasting millions of years is unclear,” the summary explained.
To find an explanation, the team explored the potential effects a rapid TPW would have on ancient sea levels. This included what the summary described as “predictable, globe-spanning patterns of continental flooding and exposure.”
“Rapid TPW will induce global sea level fluctuations associated with relative changes in centrifugal potential, offering an independent test,” they explained.
An analysis of maps at 10-million-year intervals, combined with statistical modeling, helped the team identify several patterns. Critically, they noted the patterns were “consistent with rapid TPW over the past 320 million years.”
“We evaluated this prediction using continental flooding reconstructions and identified multiple robust quadrupolar patterns since 320 million years ago,” they wrote.
These four rapid TPW ancient sea-level ‘signals’ included separate events in the mid-Cretaceous (100–90 million years ago) and Late Jurassic–Early Cretaceous (150–140 million years ago).
Results Challenge Previous Explanations
When discussing the study’s results, the researchers said, “These findings broadly corroborate earlier paleomagnetic and plate-motion studies that have suggested rapid TPW.” They also noted their work confirms that “couplings among Earth’s rotational dynamics, mantle processes, and surface environments can be strongly episodic,” rather than spread out over longer time spans.
When addressing alternate theories, the team said their work found little evidence for rapid TPW events during most of the Cenozoic period and no significant signal supporting the alternative theory that rapid northward movement of the supercontinent Pangea was driven primarily by TPW during the late Carboniferous and Permian, “challenging that proposed explanation.”
Christopher Plain has spent the last six years as Associate News Editor and Head Science Reporter at The Debrief. Follow and connect with him on X, learn about his novels at plainfiction.com, or email him at christopher@thedebrief.org.