Researchers detail Earth's magnetism

new technique for measuring the Earth's magnetic field back to the days of the dinosaurs developed by University researchers indicates that the magnetic field of prehistoric Earth was as much as three times stronger than previously thought.

The new method, developed by a team led by John Tarduno, professor of geophysics and chair of the Department of Earth and Environmental Sciences, could help scientists better understand ancient Earth as well as provide new insights into how magnetic fluctuations may have affected the development of life on the planet

The results of the first field test of the new technique appeared in the March 2 issue of Science.

"We know a lot about the directions of the Earth's magnetic field," says Tarduno, first author of the Science paper. "It's how we unravel plate tectonics and learn something about the core. But to understand the way the field works, you also need to know the field's magnitude, and we don't know nearly enough about that."

Captured in tiny pieces of magnetic particles in new lava, the record of the magnetic field indicates that the magnetic poles have flipped several times during Earth's lifetime--meaning a compass 100,000 years ago could have pointed south instead of north.

The traditional approach to measuring ancient Earth's magnetic field strength, called "paleointensity," was developed more than four decades ago, and has changed little until now.

Using the University's Superconducting Quantum Interference Device (nicknamed "SQUID"), a device normally used in computing chip design that is extremely sensitive to the tiniest magnetic fields, Tarduno and his team were able to test the strength of the magnetic field on samples the size of a grain of sand. The approach limited the possibility of contamination, resulting in more accurate measurements.

"Our findings suggest that there is a relationship between magnetic reversals and paleointensity," says Tarduno. "Such a relationship fits very well with supercomputer models. It's an exciting time. We're really starting to understand how the heart of our planet works."

University postdoctoral student Rory Cottrell and graduate student Alexei Smirnov also were authors on the Science paper.

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