A study from Tel Aviv University, Hebrew University of Jerusalem, and the University of California San Diego has recently showed that we shouldn’t worry about the weakening of Earth’s geomagnetic field. After analyzing several Judean jar handles, they discovered it had been undulating for thousands of years.
The data from the well-dated jar handles indicates that changes occurred in the strength of Earth’s geomagnetic field. The fluctuations occurred between 8th and 2nd century BC and they peaked throughout the 8th century.
This discovery is meant to complete a 2009 study that found evidence of an unusually strong geomagnetic field during the Iron Age. Dr. Erez Ben-Yosef, from the Institute of Archaeology of Tel Aviv University, stated that this field was the strongest recorded in the past 100,000 years. Thus, the recent weakening of the field is not worrying, since the field appears to have changed in intensity throughout the millennia.
The study is based on the analysis of 67 ceramic jar handles impacted by heat which bear royal stamps from the 8th to the 2nd century BC, thus providing an accurate way to establish their age. The jars date from the Iron Age until the Hellenistic Period of Judea and the researchers were to see how the field evolved and fluctuated in this timespan.
They performed several experiments to measure the geomagnetic intensity. They built an oven from the model of the ancient ones in which the jars were manufactured and they used a superconducting magnetometer.
But how can ceramics be indicators of magnetic field? The researchers explained that anything that was heated in an oven and then cooled had some tiny minerals that hosted information about the geomagnetic field of the time the clay came from. Any geological material that was once hot and then cooled can have these minerals, even lava.
In turn, the changes in the geomagnetic field can be used as advanced dating methods, besides radiocarbon dating. The Levantine archaeomagnetic record can be used to date artifacts which were heat treated.
Thus, the new data can help both geologists and archaeologists. It can provide information on the core-mantle interactions and other geological processes and, at the same time, can be used to date artifacts. The scientists are currently trying to gather more archaeomagnetic information on Levant and find out more on the changes in the geomagnetic field.
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