The study, published December 18 in the Proceedings of the National Academy of Sciences (PNAS), focuses on ancient bricks bearing the names of Mesopotamian kings. These bricks provided the key to understanding a strange anomaly in the Earth’s magnetic field that appeared three thousand years ago.

Details of the study

The team, led by Professor Matthew Howland from Wichita State University and co-author Professor Mark Altavil from the UKL Institute of Archaeology, used a technique known as “archaeomagnetism” to recognize signatures of the Earth’s magnetic field in these archaeological objects.

The method aims to increase the accuracy of dating artifacts that do not contain organic matter, especially for traditional dating methods such as radiocarbon dating.

This work helps provide an important dating foundation that will enable others to benefit from absolute dating using archeomagnetism.
– Professor Altavel explained.

How does it work

The method involves analysis of the latent magnetic signature in iron oxide grains in clay bricks originating from various archaeological sites in Mesopotamia, now located in the territory of modern Iraq.

When the bricks were first fired, the strength of the Earth’s magnetic field was reflected in the minerals, providing a unique historical map of changes in the magnetic field over time. Researchers have successfully confirmed the existence of the “Iron Age Levantine Geomagnetic Anomaly”, a period marked by an extremely strong magnetic field in modern-day Iraq between 1050 and 550 BC.

Professor Howland, the lead author of the study, emphasized the importance of the study as follows:

By comparing ancient artifacts with what we know about ancient magnetic field conditions, we can estimate the dates of artifacts heated in ancient times.

How did the researchers work?

The team’s advanced techniques included carefully chipping small pieces of brick and using a magnetometer to precisely measure the pieces. The resulting data not only confirmed the existence of the anomaly, but also provided archaeologists with a new tool for dating artefacts at a higher resolution than traditional radiocarbon dating.

The study also resolved historical ambiguities by aligning the methodology with the known chronologies of the kings’ reigns, specifically following the “Low Chronology”. In addition, the team observed significant changes in the Earth’s magnetic field from 604 to 562 BC, during the reign of Nebuchadnezzar II; this suggests rapid increases in density over a relatively short period of time.

This research opens new ways to understand Earth’s magnetic history and refine the dating of ancient artifacts, offering a glimpse into the magnetic secrets hidden in ancient building materials.