A breakthrough achieved by researchers from four Israeli universities will enable archaeologists to identify burnt materials discovered in excavations and estimate their firing temperatures. Applying their method to findings from ancient Gath (Tell es-Safi in central Israel), the researchers validated the Biblical account: “About this time Hazael King of Aram went up and attacked Gath and captured it. Then he turned to attack Jerusalem” (2 Kings 12, 18). They explain that unlike previous methods, the new technique can determine whether a certain item (such as a mud brick) underwent a firing event even at relatively low temperatures, from 200°C and up. This information can be crucial for correctly interpreting the findings.
The multidisciplinary study was led by Dr. Yoav Vaknin from the Sonia & Marco Nadler Institute of Archaeology, Entin Faculty of Humanities, at Tel Aviv University, and the Palaeomagnetic Laboratory at The Hebrew University. The paper has been published in the scientific journal PLOS ONE (https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0289424).
The new method relies on measuring the magnetic field recorded and ‘locked’ in the brick as it burned and cooled down. Dr. Vaknin: “The clay from which the bricks were made contains millions of ferromagnetic particles – minerals with magnetic properties that behave like so many tiny ‘compasses’ or magnets. In a sun-dried mud brick the orientation of these magnets is almost random, so that they cancel out one another. Therefore, the overall magnetic signal of the brick is weak and not uniform. Heating to 200°C or more, as happens in a fire, releases the magnetic signals of these magnetic particles and, statistically, they tend to align with the earth’s magnetic field at that specific time and place. When the brick cools down, these magnetic signals remain locked in their new position and the brick attains a strong and uniformly oriented magnetic field, which can be measured with a magnetometer. This is a clear indication that the brick has, in fact, been fired.
In the second stage of the procedure, the researchers gradually ‘erase’ the brick’s magnetic field, using a process called thermal demagnetization. This involves heating the brick in a special oven in a palaeomagnetic laboratory that neutralizes the earth’s magnetic field. The heat releases the magnetic signals, which once again arrange themselves randomly, canceling each other out, and the total magnetic signal becomes weak and loses its orientation.
After proving the method’s validity, the researchers applied it to a specific archaeological dispute: was a specific brick structure discovered at Tell es-Safi – identified as the Philistine city of Gath, home of Goliath – built of pre-fired bricks or burned on location? The prevalent hypothesis, based on the Old Testament, historical sources, and Carbon-14 dating attributes the destruction of the structure to the devastation of Gath by Hazael, King of Aram Damascus, around 830 BCE. However, a previous paper by researchers including Prof. Maeir, head of the Tell es-Safi excavations, proposed that the building had not burned down, but rather collapsed over decades, and that the fired bricks found in the structure had been fired in a kiln prior to construction. If this hypothesis were correct, this would be the earliest instance of brick-firing technology discovered in the Land of Israel.
To settle the dispute, the current research team applied the new method to samples from the wall at Tell es-Safi and the collapsed debris found beside it. The findings were conclusive: the magnetic fields of all bricks and collapsed debris displayed the same orientation – north and downwards. Dr. Vaknin: “Our findings signify that the bricks burned and cooled down in-situ, right where they were found, namely in a conflagration in the structure itself, which collapsed within a few hours. Had the bricks been fired in a kiln and then laid in the wall, their magnetic orientations would have been random. Moreover, had the structure collapsed over time, not in a single fire event, the collapsed debris would have displayed random magnetic orientations. We believe that the main reason for our colleagues’ mistaken interpretation was their inability to identify burning at temperatures below 500°C. Since heat rises, materials at the bottom of the building burned at relatively low temperatures, below 400°C, and consequently the former study did not identify them as burnt – leading to the conclusion that the building had not been destroyed by fire. At the same time, bricks in upper parts of the wall, where temperatures were much higher, underwent mineralogical changes and were therefore identified as burnt – leading the researchers to conclude that they had been fired in a kiln prior to construction. Our method allowed us to determine that all bricks in both the wall and debris had burned during the conflagration: those at the bottom burned at relatively low temperatures, and those that were found in higher layers or had fallen from the top –at temperatures higher than 600°C.”
https://www.aftau.org/news_item/tau-researchers-use-earths-magnetic-field-to-verify-old-testament-event/
AR #61
“Gnosis and the Secrets of Solomon’s Temple”
by Philip Gardner
