Geomagnetism has already reversed 3.2 billion years | Forbes Japan (Forbes Japan)

Albert Einstein described the origin of geomagnetism as one of the most intriguing mysteries on the planet. We now know that the Earth’s outer shell is made of a liquid alloy of iron and nickel. Earth’s rotation moves this liquid metal, generating electric currents and magnetic fields. But scientists still haven’t been able to explain exactly how it works, or more bafflingly, why Earth’s magnetic field changes its strength and even direction over time, allowing it to reverse the positions of the north and south magnetic poles.

A new study analyzing Earth’s oldest rocks shows that at least 3.25 billion years ago, the crust was pushing and pulling in a way similar to modern plate tectonics. The study also provides the first evidence of when the planet’s magnetic poles switched between north and south.

Two studies also suggested that such geological changes may have made Earth’s environment more conducive to the evolution of life.

geologist at Harvard UniversityAlec BrennerWhenRoger isStudy led by Western AustraliaPilbara Craton(Bilbara Massif). It is one of the oldest and most stable parts of the Earth’s crust. Using the latest technology and equipment, the research team searched for magnetic signatures preserved in ancient rocks and found that some of Earth’s oldest crusts grew by 6.1 cm per year and 0.55 degrees every million years. It showed it. It was moving fast and directional.

The speed and direction of this crustal motion support plate tectonics as the most plausible and powerful explanation.

In the paper, the researchers also describe what they believe is the closest evidence of a complete reversal of Earth’s magnetic field.This kind of radical changeIt’s happened a lot in Earth’s recent geological history, with magnetic poles flipping 183 times in the past 83 million years and possibly hundreds of times in the past 160 million years.NASASays.

The study argues that Earth’s magnetic field was already stable 3.2 billion years ago and strong enough to prevent solar winds from penetrating the atmosphere. Combining this insight with findings on plate tectonics provides clues about the environments in which early life arose.

“This explains that the early Earth was already magnetically mature,” Brenner said. “There, many of the same dynamic processes that made Earth a more favorable place for the emergence and development of life were taking place, with a more stable environment and surface conditions.”

paper”Plate motion and a dipole geomagnetic field at 3.25 Ga(Plate motion and Earth’s dipole magnetic field 3.25 billion years ago) Published in Proceedings of the National Academy of Sciences (2022). ArticleHarvard universityIntroduction of.

（original forbes.com）