The recorded weakening of the geomagnetic field, which extends from the Earth’s core into outer space and was first recorded 180 years ago, has raised concern by some for the welfare of the biosphere.
But a new study conducted by researchers from Tel Aviv University, Hebrew University and the University of California San Diego finds there is no reason for alarm: The Earth’s geomagnetic field has been undulating for centuries.
Data obtained from the analysis of Judean jar handles provide information on changes in the strength of the geomagnetic field between the 8th and 2nd centuries BCE, indicating a fluctuating field that the scientists now say peaked during the 8th century BCE.
“The field strength of the 8th century BCE corroborates previous observations of our group, first published in 2009, of an unusually strong field during that period,” says Dr. Erez Ben-Yosef of TAU’s Institute of Archaeology, the study’s lead investigator.
“This new finding puts the recent decline in the field’s strength into context. Apparently, this is not a unique phenomenon – the field has often weakened and recovered over [time].”
“We can gain a clearer picture of the planet and its inner structure by better understanding proxies like the magnetic field, which reaches more than 1,800 miles deep into the liquid part of the Earth’s outer core,” Dr. Ben-Yosef observes.
The new research is based on a set of 67 ancient, heat-impacted Judean ceramic storage-jar handles, which bear royal stamp impressions from what the archeologists believe to be the 8th to 2nd centuries BCE, providing the basis for their age estimates.
To accurately measure the geomagnetic intensity, the researchers conducted experiments at the Paleomagnetic Laboratory of Scripps Institution of Oceanography (SIO), University of California San Diego, using laboratory-built paleomagnetic ovens and a superconducting magnetometer.