By analyzing the orientations of the metals in a set of these jar handles with dates from 750 to 150 BCE, the scientists were able to see traces of the geomagnetic field’s behavior. What they found was startling. Sometime late in the 8th century BCE, there was a rapid fluctuation in the field’s intensity over a period of about 30 years—first the intensity increased to over 20 percent of baseline, then plunged to 27 percent under baseline. Though the overall trend at that time was a gradual decline in the fields’ intensity similar to what we see today, this spike was basically off the charts.
Writing in The New Yorker, Lawrence University geologist Marcia Bjornerud points out that this geomagnetic spike is far bigger than anything geoscientists had believed possible. “Both the height and the sharpness of the spike they recount push up against the limits of what some geophysicists think Earth’s outer core is capable of doing,” she explains. “If the eighth-century-BC geomagnetic jeté is real, models for the generation of the magnetic field need significant revision.”