Ancient Earth Had Magnetic FieldJohn Tarduno decided to see if he could use the University's Superconducting Quantum Interference Device (nicknamed "SQUID"), a device normally used in computing chip design, which is extremely sensitive to the tiniest magnetic fields. Tarduno's team took samples from a 1955 lava flow in Hawaii and tried to determine if the paleointensity reading would match the actual Earth's magnetic field strength in 1955. It did. With the method tested, it was time for Tarduno to see what it revealed about the magnetic field back in the days of the dinos. His team took dozens of samples from lava flows in India that were nearly 100 million years old-an unusual time in Earth's history when the field was not reversing-and found that the intensity of the field was three times stronger than the old method suggested.
3x Stronger Than Once Thought
by Jonathan Sherwood
Poles apart[T]he magnetic poles move more than 45° away from their original location and then return to it. During such "excursions", the field strength can vary enormously over just a few thousand years. "The magnetic field has lost half its strength since Roman times," says David Gubbins, a geophysicist at the University of Leeds... He thinks the fluid iron in the outer core is responsible for the excursions. The magnetic field changes in response to the flow of the liquid iron, which typically moves 10 or 20 kilometres per year.
by Charles Seife
10 April 1999