Ancient sea levels record four fast episodes of true polar wander in the past 190 million years
Mathew Domeier's University of Oslo team finds four fast bursts of true polar wander recorded in ancient sea levels over the past 190 million years. During those bursts, he says, the poles moved faster than most tectonic plates do, fast enough to possibly affect climate.
The Scientist · Science desk
What happened
- Earlier evidence for polar wander came mostly from magnetism locked in ancient rocks, and it gave conflicting answers on how often and how far the poles moved.
- The team looked for a beach-ball pattern in which sea level rises in half of each hemisphere and falls in the other, reversed between north and south, a signature Domeier says no other Earth process makes.
- Each burst lasted roughly 10 million years, at about 20, 90, 140 and 190 million years ago.
- True polar wander is still going on, and Domeier says satellites measure it at about 10 centimetres a year.
Why it matters
- What's now possible capability Coastline records date polar-wander episodes using a different physical system from magnetised rock, so episodes proposed from the conflicting magnetic data can now be confirmed or contested.
- What it limits constraint Only motion faster than about 0.6 degrees per million years shows up, so four is a count of fast episodes, and slower wander remains outside what this record can detect.
- Who has to decide decision Anyone reading latitude-sensitive climate records from near 20, 90, 140 or 190 million years ago now has a second explanation for a latitude change to weigh: the whole shell slipping faster than most plates drift.
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In true polar wander, the moving part is Earth's outer shell of crust and mantle, 2800 kilometres thick, which shifts relative to the spin axis, according to Sabin Zahirovic at the University of Sydney [15]. Plate tectonics and mantle convection slowly move mass around inside the mantle and change how the planet spins [2]. The solid outer layers then shift until Earth settles into a new stable spin, and that moves the geographic poles to new positions on the surface [4]. "The crust and the mantle effectively slip over the core during a true polar-wander event," Domeier said [5].
Sea level can record this because water and rock respond at different speeds. Ocean water adjusts to a change in centrifugal potential faster than the rocky sea floor does [7]. For a while during an event, the sea surface takes its new shape over a floor that has not yet caught up. Domeier's team searched the geological record of sea-level change for the trace of that offset [1].
The effect size is a threshold, not a measurement. "We cannot estimate the exact speed, but we can recognise events where the rate of polar motion exceeded about 0.6 degrees per million years," Domeier said [11]. If that rate held across a full 10-million-year burst [3], it adds up to about 6 degrees of polar motion [17]. Because 0.6 is a floor on the rate, 6 degrees gives only a rough scale for the episodes. The gaps between the four dates are 70, 50 and 50 million years [18], too few intervals to call a cycle.
New Scientist's report says the poles wander more than we had thought [14]. What "we had thought" rests on is the magnetic rock record, which had given conflicting results on how often and how far [6]. The report does not give the journal, the number of sea-level records, a prior estimate, or how far each event moved the pole, which is the figure a plate reconstruction would need.
In my view the method matters more than the four dates it has produced so far. The stakes the researchers name are climate and sea level. "This is a very exciting development that helps us link very deep Earth processes to changes in long-term climate and sea level on the planet," Zahirovic said [16].
What to watch
- Whether the four sea-level dates line up with polar-wander episodes previously proposed from paleomagnetic data, or contradict them.
- Per-event magnitudes in degrees from the full paper, which would show how far latitude-based plate and climate reconstructions need to move.
- Whether the sea-level fingerprint can be read in records older than 190 million years.
Clarity's read
What the record supports and how the coverage leans. The claims behind it follow.
Reality
- Evidence70
- Adoption
- Not scored
- Hype gap+20
- Incentives
- Not scored
- Confidence65
Perspective Coverage
3 publishers- Builder
- Builder 62%
- Operator
- Operator 25%
- Investor
- Investor 13%
Claim ledger
Ranked by verification strength, evidence, and original report placement.
- [1]
Mathew Domeier at the University of Oslo and his team analysed the geological record of sea-level change, looking for distinctive signals expected during a true polar-wander event.
- [2]
True polar wander is driven by the way plate tectonics and mantle convection slowly redistribute mass in Earth's mantle and affect the planet's spin.
- [3]
From ancient sea-level patterns, Domeier and colleagues found that the geographic poles moved dramatically, over periods of around 10 million years, four times: at 20, 90, 140 and 190 million years ago.
- [4]
When the planet's spin is thrown out of balance, the solid outer layers move to help Earth find a new stable spin equilibrium, which moves the geographic poles.
- [5]
"The crust and the mantle effectively slip over the core during a true polar-wander event,"
- [6]
Until now much of the evidence for true polar-wander events came from ancient magnetic data locked inside rocks, and this evidence yielded confusing and conflicting results about the frequency and scale of the events.
- [7]
Because ocean water adjusts more quickly to centrifugal potential changes than the rocky sea floor, true polar-wander events are expected to leave a telltale pattern in sea level.
- [8]
During true polar wander, sea level rises in one half of the northern hemisphere and falls in the other, and likewise in the southern hemisphere, with the northern and southern signals reversed, creating a beach ball-like global pattern.
- [9]
"This is a very strange pattern that is not caused by other Earth processes,"
- [10]
The study demonstrates that clues in coastline change provide an independent fingerprint of true polar wander.
- [11]
"We cannot estimate the exact speed, but we can recognise events where the rate of polar motion exceeded about 0.6 degrees per million years."
- [12]
Domeier says this rate is faster than the rate at which most tectonic plates move, fast enough to potentially have an effect on climate systems.
- [13]
True polar wander continues today; Domeier says it is measurable by satellites at a rate of about 10 cm per year.
- [14]
New Scientist reports that Earth's geographic poles wander more than had been thought and may be far less immutable than previously known.
- [15]
Sabin Zahirovic at the University of Sydney says very few people are aware that Earth's 2800-km-thick outer shell of crust and mantle is in motion with respect to Earth's spin axis.
- [16]
"This is a very exciting development that helps us link very deep Earth processes to changes in long-term climate and sea level on the planet,"
- [17]
If polar motion held at the 0.6 degrees per million years detection threshold across a full 10-million-year episode, the pole would move about 6 degrees.
- [18]
The intervals between the four events are 70, 50 and 50 million years.
Sources
3 independent publishers whose own reporting we read for this story.
- newscientist.comEarth’s geographic poles wander more than we had thought
1 article · October 1, 2026
- phys.orgAncient sea levels reveal when the Earth's poles went wandering
1 article · October 2, 2026
- scientificamerican.comScientists discover that Earth’s crust has repeatedly rolled over—and it’s still happening
1 article · October 1, 2026
Topics and entities
Topics
- True polar wander
- Sea-level history
Entities
- University of Oslo
- Giovanni Muttoni
- Science
- University of Milan
- University of Sydney