Scientists from the Institute of Life and Earth Sciences (ELSI) of the Tokyo Institute of Technology discovered evidence in Italy that confirms the inclination of the Earth’s crust about 84 million years ago: it would have moved exactly 12 degrees south. According to the new study, the oscillation of the hard outer layer of the Earth has occurred to a much greater degree over time than previously thought.
According to a Press release, limestone in the Apennines of Italy left microscopic spots and tracks indicating that the earth’s crust “wobbled” during the Cretaceous. However, the mantle returned to its original position by moving almost 25 degrees. The research was recently published in the journal Nature Communications.
A constantly moving outer layer
Precisely, the theory known as “True polar shift” suggests that Earth’s outer mantle can tilt independently because it surrounds a layer of molten liquid and an interior of solid metal. This phenomenon can occur on different planets or moons, marking the geographic locations of the north and south poles to change or “drift.”
When a body is not totally rigid, as in the case of the Earth, it undergoes different variations in its outer layer, independently of its axis of rotation. At that time, a polar deviation will occur: the planet or moon will oscillate to produce a planetary reorientation, modifying the orientation of its magnetic poles.
The Japanese researchers explained that all the rocky layer of the planet, the mantle and the solid crust, are rotating around the liquid outer core, thus producing the polar deviations. This phenomenon has happened on different occasions throughout the geological history of the Earth, much more than we have thought until today: it is what would have happened about 80 million years ago and has been recorded in Italy.
The researchers analyzed paleomagnetic data, through which you can study the Earth’s magnetic field in the past. They focused on footprints discovered in the pink limestone Scaglia Rossa, located in the Apennines of central Italy and originating in the Cretaceous period, around 145.5 to 65.5 million years ago.
According to the scientists, the analyzed limestone reveals a change in latitude through which the region of present-day Italy briefly moved towards the Equator between 86 and 80 million years ago, coinciding with the rotation observed from the magnetic data. . Indeed, the report of the specialists suggests that the Earth crust it has moved slowly about three degrees every million years.
Experts believe that this is evidence of the last great “true polar shift” suffered by the Land, indicating that the axis of rotation of the planet has not remained as stable as previously thought. What’s more: previous research suggests that polar shift may have caused the last Ice Age from Earth about 3.2 million years ago, the effects of which would still be ongoing.
According to a Article published in the Daily Mail, in the last 12 million years the displacement of the Earth in relation to its axis managed to push Greenland towards the North Pole, in sufficient magnitude to start an ice age that would continue today. Data from the magnetic signature of the oceanic crust and fossil signatures from the depths of the Pacific would be some of the evidences of this process.
A Late Cretaceous true polar wander oscillation. Ross N. Mitchell, Christopher J. Thissen, David A. D. Evans, Sarah P. Slotznick, Rodolfo Coccioni, Toshitsugu Yamazaki and Joseph L. Kirschvink. Nature Communications (2021).DOI:https://doi.org/10.1038/s41467-021-23803-8
Photo: High resolution image on the road cut west of the Apiro Dam lake, in the central Apennines of Italy. This particular location crosses the boundary of a major geomagnetic inversion, known as the Chron 33R / 33N transition, which dates to about 80 million years ago. A surprisingly high fraction of oriented samples from these locations produce excellent records of the ancient magnetic field at the time they were formed. Credit: Ross Mitchell.
Eddie is an Australian news reporter with over 9 years in the industry and has published on Forbes and tech crunch.