Ancient jars and amphora handles from Jerusalem and the Greek island of Rhodes, are helping researchers uncover changes in Earth’s magnetic field more than 2,000 years ago. A new study of Hellenistic pottery has revealed evidence of a sharp drop in magnetic field strength during the second century BCE and may also help archaeologists improve the dating of ancient artifacts and historical sites.
The study, led by Yael Hochma and published in Archaeometry, analyzed ceramic artifacts dating from the third to the first centuries BCE. The team examined local storage jars from Jerusalem and stamped amphora handles imported from Rhodes, one of the most important trade centers in the ancient Mediterranean.
Ancient pottery preserves a magnetic record
When pottery is fired in a kiln, magnetic minerals inside the clay record the strength of Earth’s magnetic field at that moment.
Researchers can later measure this magnetic signal to reconstruct past changes in the field. This method, known as archaeomagnetism, has become an important tool for both geophysics and archaeology.
Rhodian amphora handles offer precise dating
The study focused on pottery recovered from several excavation sites in Jerusalem, including the City of David, the Jewish Quarter, and the Givati Parking Lot excavation.
Many of the Rhodian amphora handles carried official stamps that identified manufacturers and government officials. Because some of these officials served for only a single year, the handles can often be dated with unusual precision.
That level of accuracy is rare in archaeomagnetic research. In some cases, the Rhodian stamps allow researchers to link magnetic measurements to very short time intervals, enabling them to track short-term changes in Earth’s magnetic field.
Researchers identify a sharp magnetic decline
After testing the ceramic samples, the researchers found clear evidence that magnetic field intensity declined sharply during the early second century BCE.
A new study of Hellenistic pottery from Jerusalem and Rhodes found evidence of a dramatic weakening of Earth's magnetic field around 220–160 BCE. The findings could also help archaeologists date ancient artifacts and historical sites with greater precision. pic.twitter.com/vATBhbqyle
— Tom Marvolo Riddle (@tom_riddle2025) June 22, 2026
Measurements showed a drop from very high levels around 220 BCE to significantly lower values by about 160 BCE. The findings match recent studies from the Levant that reported a similar pattern.
The results suggest that Earth’s magnetic field weakened much faster during that period than some regional magnetic models currently indicate. Researchers said such rapid changes are often difficult for large-scale models to capture because those models tend to smooth out short-lived fluctuations.
Magnetic data helps refine artifact chronologies
The Rhodian handles provided another important benefit. Their precise dating allowed the team to compare magnetic measurements with existing archaeological chronologies.
In some cases, the magnetic data helped narrow the likely production dates of individual amphora handles. The researchers said this shows how archaeomagnetic evidence can support traditional dating methods based on pottery styles, inscriptions, and archaeological context.
The study also examined locally produced storage jars from Jerusalem. Although these vessels cannot usually be dated as precisely as the Rhodian handles, they still provided valuable information about magnetic field conditions in the southern Levant during the Hellenistic period.
Clues emerge from a debated Jerusalem site
One sample drew particular attention. It came from a storage jar found in the foundation of a defensive structure at the Givati Parking Lot excavation.
Some archaeologists have linked the structure to the Seleucid Akra, a fortress traditionally associated with King Antiochus IV.
The magnetic evidence suggests the jar was likely produced during the late second century BCE, supporting conventional pottery dating and adding new information to the debate over the site’s chronology.
Findings connect regions across the eastern Mediterranean
Beyond archaeology, the findings contribute to a larger scientific question about how magnetic field variations were distributed across the eastern Mediterranean. Rhodes sits between the southern Levant and the Balkans, allowing researchers to compare magnetic records from different regions.
The team found that the overall magnetic trends were remarkably similar across these areas. The results suggest that large parts of the eastern Mediterranean may have shared broadly comparable magnetic signals over distances exceeding 1,000 kilometers.
That conclusion could help scientists build more reliable regional magnetic curves for future dating studies.
Thousands of artifacts could expand future research
Researchers said thousands of stamped Rhodian amphora handles remain available for study across the Mediterranean. Those artifacts could provide an extensive archive for future archaeomagnetic research and offer an increasingly precise record of both human history and Earth’s changing magnetic field.
The findings show that ordinary pottery fragments can preserve more than evidence of ancient daily life. They also capture a record of Earth’s changing magnetic field, offering researchers a rare tool for studying both human history and planetary processes.
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