Almost 3,000 years after the supposed destruction of a major Philistine city, the event – which is mentioned in the Old Testament – has finally been corroborated thanks to a new technique that detects ancient magnetic fields in burnt bricks. In addition to confirming that a building in the area was indeed ravaged by a fire, the research also settles the argument over whether or not the Biblical inhabitants of the Levant had developed the technology to fire mud bricks in a kiln.
According to the Second Book of Kings, the mighty city of Gath was captured and ransacked by the forces of Hazael, king of Aram-Damascus. Radiocarbon dating of a “well-defined destruction layer” within the archaeological site of Tel es-Safi has since suggested that the event took place around 830 BCE.
However, in 2011, an analysis of a toppled wall within the Tel muddied the picture somewhat, as the authors determined that the structure had crumbled over many decades rather than in a single violent event. They went on to suggest that while the mud bricks showed signs of having been exposed to high temperatures, this probably occurred when they were fired in a kiln prior to the wall’s construction.
Such an interpretation is at odds with the widely accepted notion that kiln-fired mud bricks only became widespread in the Levant during Roman times, and that prior to this, structures were typically built with sun-dried bricks. In an attempt to straighten things out, the authors of a new study developed a novel method to determine whether ancient materials were subjected to firing.
Describing the method in a statement, study author Dr Yoav Vaknin explained, "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.”
“Heating to 200°C [392°F] 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,” he said. Thus, unlike sun-dried clay, a fired 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.”
It therefore stands to reason that if the wall was destroyed in a fire, all of the bricks would have recorded the direction of the Earth’s magnetic field at the exact time and place of the event. Of course, kiln-fired bricks also pick up this magnetic field as they are fired; yet during the wall’s construction, each brick would have been laid in a random orientation, meaning that they would have ended up with magnetic fields pointing in multiple directions.
To determine whether the bricks’ fields were aligned or not, the study authors used a technique called thermal demagnetization. This involves heating the clay in a special oven that neutralizes the Earth’s magnetic field.
During this process, the material becomes demagnetized when exposed to the same temperature that originally caused it to magnetize. Using this method, the researchers were able to determine the exact temperatures that the bricks were initially heated to, while also confirming that their magnetic fields all pointed in the same direction.
"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,” explains Vaknin. “Had the bricks been fired in a kiln and then laid in the wall, their magnetic orientations would have been random.”
In addition to corroborating the Biblical account of the city’s destruction, the study also illustrates that the bricks were sun-dried and not kiln-fired. The idea that such technology only arrived with the Romans is therefore supported.
"Our findings indicate that the brick firing technology was probably not practiced in the Land of Israel in the times of the Kings of Judah and Israel," concludes study author Erez Ben-Yosef.
The study is published in the journal PLOS ONE.