Detailed research of thousands of ancient rock samples confirmed a bold hypothesis.
- Earth’s solid crust – the crust and the mantle – “slip” over the liquid outer core.
- The uneven distribution of the Earth’s masses can lead to the skew of this crust.
- We know many examples of such a “tilt” or “sideward turn” of space.
- A new study has verified and confirmed the occurrence of this event in Earth’s history.
The movement of the continents, or more specifically the plates of the continental crust, is a known and measurable process.
However, over the past decades geologists have discussed a different kind of Earth’s motion – a large and geologically surprising deviation of our planet’s solid “crust” from the Earth’s axis (the planet’s rotation axis).
So far, there has been a lack of evidence for the so-called true polar wander. Study changes that published in the prestigious scientific journal Nature Communications. They provide the most compelling results yet, supporting the assumption that at the end of the Mesozoic era, our planet flipped sideways, so to speak.
The distribution of land masses is not completely uniform. Irregularities occur due to the location of the territories and chains of large volcanoes, as well as continental glaciers. Below the surface, specifically in the Earth’s mantle, these are, for a change, the resting plates of the ocean floor.
The crust and the Earth’s mantle form a kind of hard crust, underpinning the liquid core of the Earth. Since physical forces push the “excess mass” to the center of the axis of rotation, that is, to the equator, changes in the distribution of Earth’s masses can theoretically cause the entire solid “crust” to shift relative to the Earth’s core and Earth’s axis.
“When viewed from space, it will look as if the Earth has flipped sideways,” said geologist and lead author of the new study, Joe Kirschvink of the Tokyo Institute of Technology. “In fact, only the stony crust of the planet – the solid Earth’s mantle and crust – will move,” he adds.
There will be feet
Importantly, such a “planetary reversal” would also be reflected in the geological record.
Some minerals, such as iron-containing magnetite, act as a compass frozen in time. They record the location of the magnetic poles at the time of their hardening.
Because the Earth’s magnetic field is created by processes that occur in the liquid outer core, deep under the Earth’s hard crust, the rock sequence will capture the apparent abrupt pole shift.
True, in fact, neither the poles nor the continents will move, but the solid crust of the entire Earth, the mantle of the Earth with its crust.
Check the controversial hypothesis
True polar wandering has been documented in the case of Mars, as well as in the case of several months of the Solar System. At Jupiter’s moon, Europa reaches 80 degrees.
The real trip of the poles also occurs on Earth, but to a small extent. But according to one hypothesis, this was not always the case.
At the end of the Mesozoic Era, about 84 million years ago (18 million years before the extinction of the dinosaurs), a major shift in Earth’s hard crust was due to occur. This hypothesis sparked heated debate.
An international team of geologists, led by Joe Kirschvinik, decided to test this hypothesis with the most accurate and consistent research to date based on the rocks of the Italian Apennines. This is where suitable types of ideally aged rocks come into play.
The researchers took and analyzed up to a thousand samples.
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“These sedimentary rocks from Italy are very special and very reliable,” says study co-author Sarah Slotznikova. The scientist explains that “the magnetic minerals being studied are actually fossilized bacteria in which magnetite metal chains were formed.”
In contrast to some older studies that questioned the true journey of Earth’s poles, Kirschvink’s team worked with a wider time variance and about ten times the number of samples. In total, he analyzed more than a thousand rock samples dating from 86 to 76 million years ago.
The samples came from different outputs of relatively old layers. In this way, geologists were able to verify the results of one data set using another set.
Finally, data from both outputs yielded identical results.
“The two examined stratigraphic sequences clearly confirm the presence of true pole wandering,” the authors wrote in the study.
there and back
As posited by the “tilting Earth” hypothesis, mineralomagnetic analysis revealed that the Earth’s solid crust was tilted by about 12 degrees 84 to 82 million years ago.
The territory of present-day Italy temporarily reached low latitudes during this fluctuation. However, over the course of five million years, the axis has returned to its original slope.
“The searched rock record at a new high resolution not only indicates a single episode of the true voyage of the poles, but also indicates a return to its original position,” the authors wrote in the study.
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