Washington: Scientists have put a certain controversy to rest, by ascertaining that in ancient times, the Earth’s magnetic field was structured like the two-pole model of today, which suggests that the methods geoscientists use to reconstruct the geography of early land masses on the globe are accurate.
The findings may lead to a better understanding of historical continental movement, which relates to changes in climate.
By taking a closer look at the 1.1 billion-year-old volcanic rocks on the north shore of Lake Superior, the researchers have found that Earth’s ancient magnetic field was a geocentric axial dipole - essentially a large bar magnet centered in the core and aligned with the Earth’s spin axis.
Some earlier studies of these rocks had led other teams to conclude that the magnetic field of the ancient Earth had a far more complex structure - some proposing the influence of four or even eight poles - implying that present models of the supercontinents that relied on paleomagnetic data and an axial dipole assumption were wrong.
The report said that previous efforts to interpret the ancient geomagnetic field in rocks from North America were confused by the rapid migration of the continent toward the equator in the distant past.
The researchers “neatly lay to rest the long-standing controversy over the nature of Earth’s magnetic field 1.1 billion years ago,” according to geoscientist Joseph Meert of the University of Florida in an essay that accompanies the report.
“In this paper, we show that Earth’s magnetic field has been more stable in the past than originally believed,” said Adam Maloof, an assistant professor of geosciences at Princeton and one of the paper’s authors.
The scientists plan to use the data to better understand how continents moved in the distant past, massing to form supercontinents.
“We needed to be able to have a working model of how the geomagnetic field behaved in the past if we are going to talk about where plates have moved, how fast they’ve moved and how ancient supercontinents were configured,” said Nicholas Swanson-Hysell, a graduate student at Princeton and the first author on the paper.
According to Maloof, knowing the proper location of continents is key to understanding the climate of any era because the shape and location of continents affect ocean currents, global average temperatures and wind patterns.
By understanding in detail what Earth’s climate was like in ancient times, scientists can better comprehend the climate of today and make more accurate projections for the future.