Magnetic insights from Mesopotamian bricks unravel ancient anomalies

Ancient bricks, bearing the names of Mesopotamian kings, have offered intriguing insights into a puzzling anomaly in Earth’s magnetic field 3,000 years ago, as per a recent study involving researchers from University College London. Published in the Proceedings of the National Academy of Sciences, the research delves into how alterations in the Earth’s magnetic field left imprints on iron oxide grains within clay bricks, with scientists reconstructing these changes based on the inscribed kings’ names.

The study introduces the concept of “archaeomagnetism,” which seeks magnetic field signatures in archaeological items. This innovative approach not only contributes to understanding Earth’s magnetic history but also aids in more accurately dating artifacts lacking organic material. Professor Mark Altaweel from UCL Institute of Archaeology emphasized the significance of this work in establishing a crucial dating baseline for materials like bricks and ceramics.

Over time, Earth’s magnetic field fluctuates, leaving a distinctive signature on magnetic-sensitive minerals. The research analyzed the magnetic signature in iron oxide grains within 32 clay bricks from Mesopotamian sites, offering a historical map of the Earth’s magnetic field changes. The study confirmed the existence of the “Levantine Iron Age geomagnetic Anomaly,” shedding light on a period when the magnetic field was unusually strong around modern Iraq from approximately 1050 to 550 BCE.

Lead author Professor Matthew Howland explained that by comparing artifacts to the known conditions of the magnetic field, researchers can estimate the dates of heated artifacts. The technique, measuring iron oxide grains, provides a new tool for dating ancient artifacts with better resolution than radiocarbon dating.

Aside from dating artifacts, archaeomagnetic dating helps pinpoint the reigns of ancient kings more precisely. The study aligned with the archaeological community’s understanding of the “Low Chronology” of certain kings, resolving ambiguities in their reigns caused by incomplete historical records.

Additionally, during the reign of Nebuchadnezzar II (604–562 BCE), the study identified dramatic changes in the Earth’s magnetic field in five samples, suggesting the possibility of rapid intensity spikes.

Co-author Professor Lisa Tauxe of the Scripps Institution of Oceanography highlighted the unique opportunity presented by well-dated archaeological remains, particularly bricks inscribed with specific kings’ names, to study changes in the geomagnetic field with high time resolution. The research unveils the potential of archaeomagnetism to unlock secrets of Earth’s magnetic past and refine the dating of ancient artifacts, enhancing our understanding of the dynamic interplay between human history and the planet’s magnetic forces.

Source: University College London

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