The Earth’s magnetic poles are not fixed. That is to say, since the formation of our planet, the magnetic South Pole that we know today was in fact… the North Pole! And vice versa, for a good number of years. Researchers even claim that we have missed such reversals, however massive they may be.
It must be said that these inversions do not follow a regular rhythm, which does not make the task of scientists easier. At the end of the Jurassic, for example, they occurred approximately once every 100,000 years, before becoming increasingly rare, until half as recently. Well, that’s what we thought.
A new study, published February 23 in the scientific journal Geophysical Research Letters, shows that we have actually probably missed some of these reversals.
Analyzing these profound changes to our planet means first analyzing the rocks. When iron-rich basalts cool after a volcanic eruption, their minerals align according to the local magnetic field and form “zebra stripes” indicating north or south, depending on the time of formation. These archives, the basis of the analysis, are however incomplete. In some areas, the oceanic crust is too thin or eroded and inversions remain invisible. Many inversions could therefore have been neglected, explains the British online media IFLScience.
New results, new reversals
Recently, for example, a team of scientists in Ethiopia discovered inversions on basalts around 30 million years old that had escaped all previous measurements. A case that might not be the only one.
Fortunately, IFLScience reports that researchers have recently been able to fill these gaps using advanced statistical methods, such as adaptive bandwidth kernel density estimation (AKDE). They were able to spot previously invisible reversals and adjust the timing of magnetic shifts.
Result? The frequency of reversals is actually much more regular and consistent than we thought! Additional studies should confirm these recent findings. If, by revealing these “invisible” shifts, researchers shed new light on the Earth’s magnetic history, the underlying mechanisms remain shrouded in mystery.
What is causing our planet to tilt like this? We know… next to nothing. An old theory, supported by the study authors, suggests that the inversions could be influenced by heat flow at the boundary between the Earth’s core and the mantle. The new method for analyzing magnetic reversals could provide new answers and, perhaps, predict future reversals.
