“The last time that Earth’s poles flipped in a major reversal was about 780,000 years ago, in what scientists call the Brunhes-Matuyama reversal.”
http://www.nasa.gov/topics/earth/features/2012-poleReversal.html
“The last time that Earth’s poles flipped in a major reversal was about 780,000 years ago, in what scientists call the Brunhes-Matuyama reversal.”
http://www.nasa.gov/topics/earth/features/2012-poleReversal.html