In 2008, what seemed like a piece of ancient "trash" — a hunk of copper slag — turned out to be a scientific goldmine. Archaeologist Erez Ben-Yosef and geologist Ron Shaar discovered the strongest magnetic field anomaly ever recorded, concealed within the waste of an Iron Age smelting site. This discovery, now known as the Levantine Iron Age Anomaly (LIAA), revealed massive magnetic field surges between 1100 and 550 B.C., shaking up our understanding of Earth's geodynamo — the engine powering our planet's protective magnetic shield. Using the cutting-edge technique of archaeomagnetism, which reads magnetic signatures "frozen" in heated artifacts such as ceramics and metal slag, the team pieced together a record of intense geomagnetic shifts previously thought to be impossible. These findings have provided scientists with a powerful new lens into Earth's inner workings, far beyond what ancient volcanic rocks have ever offered.

But the LIAA is only one piece of a much larger puzzle. As more satellites fill the sky and the threat of space radiation grows, understanding Earth's magnetic history has never been more crucial. The South Atlantic Anomaly, a mysterious weak spot in the Earth's magnetic field that disrupts satellites and space technology, may be linked to the same deep-Earth forces behind the LIAA — possibly a giant superplume roiling at the core-mantle boundary. Yet despite the promise of archaeomagnetism, the field faces major hurdles: million-dollar instruments, scarce global data, and the painstaking effort required for each sample. Still, momentum is building. New efforts in the U.S., Africa, and Southeast Asia are expanding the global magnetic map, hoping to uncover more anomalies and unlock the secrets of Earth's turbulent magnetic past — and its uncertain future.