From NASA News and Features.
A popular question for these times is the issue of the possiblity of an Earth pole shift and the effects it could have on the world. NASA clears this up for us in this article from November 2011.
Scientists understand that Earth’s magnetic field has flipped its polarity many times over the millennia. In other words, if you were alive about 800,000 years
ago, and facing what we call north with a magnetic compass in your hand, the
needle would point to ‘south.’ This is because a magnetic compass is calibrated
based on Earth’s poles. The N-S markings of a compass would be 180 degrees wrong
if the polarity of today’s magnetic field were reversed. Many doomsday theorists
have tried to take this natural geological occurrence and suggest it could lead
to Earth’s destruction. But would there be any dramatic effects? The answer,
from the geologic and fossil records we have from hundreds of past magnetic
polarity reversals, seems to be ‘no.’
Reversals are the rule, not the exception. Earth has settled in the last 20 million years into a pattern of a pole reversal about every 200,000 to 300,000 years, although it has been more than twice that long since the last reversal. A reversal happens over hundreds
or thousands of years, and it is not exactly a clean back flip. Magnetic fields
morph and push and pull at one another, with multiple poles emerging at odd
latitudes throughout the process. Scientists estimate reversals have happened at
least hundreds of times over the past three billion years. And while reversals
have happened more frequently in “recent” years, when dinosaurs walked Earth a
reversal was more likely to happen only about every one million years.
Read the rest of the article here.
Lynch, P. (2011). 2012: Magnetic Pole Reversal Happens All The (Geologic) Time. Retrieved January 16, 2013 from http://www.nasa.gov/topics/earth/features/2012-poleReversal.html
Picture Credit: Dixon Rohr