| History of the Earth's Magnetic Field: The earth's magnetic field has fluctuated greatly throughout it's history. The greatest fluctuations are the pole reversals, when magnetic North and magnetic South switch places. Paleomagnitism is the study of the history of Earth's magnetic field, when and how it changed.  The figure on the left shows how geologists can tell the orientation of the Earth's magnetic field from millions of years ago without using a time machine. Materials that are ferromagnetic can record the fields direction. When these materials encounter intense heat it causes the magnetic orientation of the material to align with the Earth's. This means, if we can find iron formed during the Triassic we can figure out how the Earth's magnetic field was orientated at the time. http://www.bio.georgiasouthern.edu/bio-home/harvey/lect/lectures.html?ccode=el&mda=scrn&flnm=cher&ttl=Earth%20over%20time 
This image shows how the Earth's magnetic
field is currently aligned. Any iron formed or given
intense heat will align itself with our current
magnetic field. For a quick slideshow explaining how the Earth has changed over the years please click HERE! |