Saturday, September 4, 2010

Earth’s Magnetic Field May Have Flipped Superfast

New evidence has been discovered that suggest Earth’s magnetic field may have flipped extremely quickly. 'Quick' is a very relative term geologically speaking. Scientists are still not sure if, nor why, but we do know that the polls switch fairly regularly. Despite what you have seen is science fiction movies, the swap will not bring the world to an end. I am curious though how certain animals that rely on the Earth's magnetic field to navigate will adapt.

"Magnetic minerals in 15-million-year-old rocks appear to preserve a moment when the magnetic north pole was rapidly on its way to becoming the south pole, and vice versa. Such “geomagnetic field reversals” occur every couple hundred thousand years, normally taking about 4,000 years to make the change. The Nevada rocks suggest that this particular switch happened at a remarkably fast clip.

Anyone carrying a compass would have seen its measurements skew by about a degree a week — a flash in geologic time. A paper describing the discovery is slated to appear in Geophysical Research Letters.

It is only the second report of such a speedy change in geomagnetic direction. The first, described in 1995 based on rocks at Steens Mountain, Oregon, has never gained widespread acceptance in the paleomagnetism community. A second example could bolster the theory that reversals really can happen quickly, over the course of years or centuries instead of millennia.
Bogue and his colleague, Jonathan Glen of the U.S. Geological Survey in Menlo Park, California, went to Nevada to study a series of well-preserved lava flows. As each flow cooled, it preserved the orientation of the magnetic field at the time, frozen like a tiny compass needle in the rock’s magnetic crystals.

One particular flow caught the scientists’ attention because it seemed to carry a complex magnetic history. This lava, Bogue says, initially started to cool and then was heated again within a year as a fresh lava flow buried it. The fresh lava re-magnetized the crystals within the rock below, causing them to reorient themselves a whopping 53 degrees. At the rate the lava would have cooled, says Bogue, that would mean the magnetic field was changing direction at approximately 1 degree per week.

The Steens Mountain rocks have been reported to preserve a change of 6 degrees per day. That rate was so high — imagine trying to navigate when a compass changes by multiple degrees per day — that many scientists challenged the report.

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