PALEOMAGNETIC TIMESCALE

HISTORY OF REVERSALS OF EARTH’S MAGNETIC FIELD (MAGNETOSTRATIGRAPHY) WAS ESTABLISHED BY RADIOMETRIC DATING OF VOLCANIC ROCKS FORMED DURING PERIODS OF NORMAL AND REVERSED MAGNETIC POLARITY

(Press & Siever)

REVERSALS ABOUT EVERY 1/2 MY

LAST MAJOR ONE ABOUT 700,000 YRS AGO