Thousands of years ago, the Earth's magnetic field experienced a significant surge in energy in a part of the planet that included the ancient kingdom of Mesopotamia.
People at the time probably didn't even notice the fluctuation, but signs of the anomaly, including previously unknown details, were preserved in the clay bricks they fired, new research has found.
When scientists recently discovered bricks from the third to first millennium B.C. Studying in Mesopotamia in the 1st century BC which included modernday Iraq and parts of modernday Syria, Iran and Turkey they discovered magnetic signatures in those dating back to the first millennium, suggesting that bricks were fired. at a time when the Earth's magnetic field was exceptionally strong.
Stamps with the names of Mesopotamian kings on the bricks allowed researchers to confirm the time delay for the magnetic peak.
Their results corresponded to a wellknown magnetic wave called the “Leventine Iron Age geomagnetic anomaly,” which occurred between 1050 and 550 B.C. occurred.
This has previously been documented in artifacts from the Azores, Bulgaria and China through archaeomagnetic analysis. It examined grains in pottery and archaeological ceramics for evidence of Earth's magnetic activity, scientists reported Dec. 18 in the journal Proceedings of the National Academy of Sciences.
“It's really exciting that ancient artifacts from Mesopotamia help explain and record important events in Earth's history, such as fluctuations in the magnetic field,” said study coauthor Mark Altaweel, professor of Near Eastern archeology and archaeology Data Science at University College London. Institute of Archeology.
“Manmade stones”
If an ancient artifact contains organic material such as bone or wood, scientists can determine its age through radiocarbon dating, which compares the decay fractions preserved in carbon isotopes.
However, for inorganic artifacts pottery or ceramic objects archaeomagnetic analysis is required to determine their age, said study lead author Matthew Howland, an assistant professor in the department of anthropology at Wichita State University in Kansas. Since ceramics are the most common type of artifact at archaeological sites around the world, this technique is an important complement to radiocarbon dating, Howland told CNN.
“Archaeomagnetic dating can be applied to any type of magnetically sensitive material that has been heated,” Howland said. And its usefulness extends beyond archaeology.
“Geologists often use rock analysis to study the Earth's magnetic fields, but in more recent times, when there is no longer any way to study very young rocks because they have not yet had time to form, we have to use archaeological artifacts “, he said. “We can think of clay bricks or ceramics as artificial stones for studying the Earth’s magnetic fields.”
Before this new study, there was little accurate archaeomagnetic evidence for Mesopotamian artifacts from this period.
“The lack of data has really limited our ability to understand the conditions of the Earth's magnetic field in this region,” Howland said. This also meant that archaeologists were unable to accurately calculate the age of many sites in Mesopotamia, “an incredibly important region in world archaeology.”
Magnetic attraction
The Earth is surrounded by a magnetosphere an invisible bubble of magnetism created by the powerful churning of molten metals in the Earth's core. It prevents our atmosphere from being destroyed by solar winds emanating from the Sun. Although the magnetosphere has been constantly present for billions of years, its strength waxes and wanes over time. (According to the US Geological Survey, human health is not directly affected by magnetic field fluctuations.)
Clay artifacts fired at high temperatures retain a “fingerprint” of Earth's magnetism at the time in minerals such as iron oxide that were affected by the magnetism.
Recovering this fingerprint requires a series of magnetic experiments that involve repeatedly heating and cooling the object, exposing it to magnetic fields, and then removing them. This process creates a series of new fingerprints that are compared to the object's original magnetic intensity.
Scientists can then assign the object to a specific period of activity in the Earth's magnetic field.
“Overall, this is exciting work because it helps us understand what the Earth's magnetic field does over time and also helps determine the age of artifacts, which would otherwise be impossible,” said Cauê S. Borlina, a postdoctoral researcher in the Department of Earth and Planetary Sciences at Johns Hopkins University.
Borlina, who was not involved in the study, researches ancient and modern magnetic fields and their effects on planet formation and habitability. “Most importantly, these highresolution recordings are critical to understanding how magnetic spikes on the surface are connected to what's happening inside the Earth,” Borlina told CNN in an email.
“Particularly in the outer core, where the Earth's magnetic field is generated.” The new analysis not only filled an important data gap, but also provided new clues about the magnetic anomaly of this time.
Of the 32 stones sampled by the researchers, five bore stamps that linked them to the reign of Nebuchadnezzar II between 604 and 562 B.C. B.C. connected. Measurements of the magnetism in the bricks showed that the magnetic field increased quickly and intensely as the bricks were made. The stamps on the bricks therefore created an instantaneous record of a wave of magnetic energy that lasted only a few decades.
“The next steps are to continue this work, apply it to additional Mesopotamian clay bricks, and further improve the curve we can create over time of Earth's magnetic field strength,” Howland said.
“But perhaps even more exciting is that archaeologists working at sites in Iraq and Syria can look at our data and apply the same techniques to undated artifacts,” he added. “This could help resolve many of the chronological debates that are taking place in the region about the chronology of kings.”
Photo credit: CNN Brasil.