About every 50,000 years, the Earth's magnetic poles flip. As basalt emerges from the ocean floor due to seafloor spreading, the iron within it aligns according to the magnetic pole's position. Paleomagnetism is the study of this magnetic orientation in ancient rocks. So, if you examine a section of seafloor and identify three areas that show magnetic pole reversals, you can determine that approximately 150,000 years have elapsed based on the frequency of those reversals.
