Ivan Seeking
Apr8-04, 05:26 PM
When North Becomes South: New Clues to Earth's Mangetic Flip-Flops
Next time Earth's magnetic field flips, compass needles will point South instead of North. But scientists can't say when it will occur, and until now they've disagreed on how long the transitions take.
A new study pins down how long it took for the last four reversals to play out. It also finds that the dramatic turnarounds occur more quickly nearer the equator than at higher latitudes closer to the poles.
...In the past 15 million years, there have been four reversals every 1 million years, or about one shift each 250,000 years, Clement explained. The last one, however, was 790,000 years ago. That might suggest we're overdue for a big change. Not necessarily so, Clement says. The flips are not periodic, meaning they don't adhere to a schedule of even intervals.
Yet the intensity of the magnetic field has been dropping for the last 2,000 years, and "it has dropped significantly" during the past two decades, Clement said. One recent study shows the decline in strength amounts to 10 percent over the last 150 years. [continued]
http://space.com/scienceastronomy/earth_poles_040407.html
Next time Earth's magnetic field flips, compass needles will point South instead of North. But scientists can't say when it will occur, and until now they've disagreed on how long the transitions take.
A new study pins down how long it took for the last four reversals to play out. It also finds that the dramatic turnarounds occur more quickly nearer the equator than at higher latitudes closer to the poles.
...In the past 15 million years, there have been four reversals every 1 million years, or about one shift each 250,000 years, Clement explained. The last one, however, was 790,000 years ago. That might suggest we're overdue for a big change. Not necessarily so, Clement says. The flips are not periodic, meaning they don't adhere to a schedule of even intervals.
Yet the intensity of the magnetic field has been dropping for the last 2,000 years, and "it has dropped significantly" during the past two decades, Clement said. One recent study shows the decline in strength amounts to 10 percent over the last 150 years. [continued]
http://space.com/scienceastronomy/earth_poles_040407.html