Science confirms: the Earth tilted to one side about 84 million years ago, when dinosaurs populated the planet
That the Earth’s magnetic poles are subject to shifts, when not even real reversals, is something long known.
The inclination of about 23° that defines the position of the magnetic poles of our planet must be the result of a specific event of “displacement of the poles” (TPW, True Polar Wander), that scientists have now identified thanks to the study of a limestone found in Italy.
The Earth tilted 84 million years ago
The research in question was published in Nature Communication and bears the signature of a research team that combines U.S. and Japanese universities and the University of Urbino. The study was in fact made possible thanks to the in-depth investigation of a particular limestone, called red flake, from Italy.
It was precisely the investigations on the red flake to exclude, in previous research, the existence of a specific event dated around 84 million years ago. Today, the new techniques available show instead – in the same sedimentary rocks – an oscillation of about 12° occurred between 86 and 78 million years ago.
There is therefore finally the proof that such an event has really happened, accompanied by a date: the shift of the Earth’s axis dates back to the Cretaceous, when dinosaurs still inhabited the Earth.
The red flake is dated between 100 and 65 million years ago, and bears the obvious traces of a shift in the Earth’s axis: fossilized bacteria trapped in the rocky sediment form chains of magnetite that would be the ultimate evidence of an axis shift in the Late Cretaceous.
When the geographic poles shift, in fact, the Earth’s surface retains important paleomagnetic data in the rocks: the rocks would be able to record, literally, the Earth’s magnetic field as it operates on the planet’s surface.
We are increasingly talking about pole reversal and a shift in the Earth’s axis of rotation, partly because the major seismic and volcanic events that have affected the world in recent years have had a clearly quantifiable impact on the position of the Earth’s poles.
Certain is that in the scientific community there was a certain preference to consider the most important events, in this sense, as extremely distant in time: according to the theories until now predominant, the axis of rotation of the Earth would be rather stable for at least 100 million years.
“This observation,” the researchers write in the paper, “is an open challenge to the notion that the axis of rotation has been essentially stable for 100 million years”: the last major movement, in fact, would date back to a much more recent geological era, even already populated by dinosaurs.
The red flake and the cosmic yo-yo
If we imagine looking at the Earth from space, explains geologist Joe Kirschvink of the Tokyo Institute of Technology, “the shift in the axis appears to be due to the Earth tilting on its side.”
“What actually happens is that the planet’s rocky layer – the Earth’s rocky mantle and crust – rotates around the liquid core.”
According to the researchers, the movement that occurred 84 million years ago was followed by a “sudden” adjustment, giving rise to a sort of “cosmic yo-yo” that in about 5 million years would have led Italy, and with it the red flake, to the equator and then back to its place.
As stated in the research “the data of the stones of Gubbio and Moria, in particular” present more than 1000 paleomagnetic data that rigorously confirm the event of 84 million years ago. The methods used to re-study the red flake rocks are defined by scientists as the most advanced methods of “demagnetization and paleomagnetic analysis” available today.
And they claim, openly, that the old investigations that denied the event were not wrong for this: there were simply too few data available. Today we can extract from a small sediment of rock the answer we’ve been looking for for a long time: the Earth tilted on its side, and it happened much more recently than we thought.