Continental Drift is defined as “the concept that all of the present continents were formerly united into larger landmasses which split apart; the pieces then drifted to assume their present shapes and positions” (Glen 167). Continental Drift was first proposed by Alfred Wagner with his first super continent that he named Pangaea, pictured above (Monroe 29). Irving was able to use his paleomagnetic data that he gathered from the field as support the concept of Continental Drift (Davis). The picture to the right illustrates the idea of Continental Drift where all of the continents were once connected in a super continent called Pangaea that later drifted apart.


   
                                                                                                                                                                                                                                                                                                                                                                                                                                      The picture above is of Wagner's first super continent,                                                                                                                                                                                                                                Pangaea (Glen 32).



                                                                                  Paleomagnetism
The picture below illustrates Earth's magnetic field (Glen 82).

    First in order to understand Paleomagnetism, a few definitions are needed. Magnetism can be defined as "a physical phenomenon resulting from the spin of electrons in some solids, particularly those of iron" and a magnetic field "is an area in which magnetic substances, such as iron are effected by lines of magnetic force emanating from a magnet" (Monroe 35). This magnetic field is caused by the Earths core, which is made up of solid iron (Glen 10). The figure to the left shows how the Earth's magnetic field looks like. Note how the Earth is similar to a giant bar magnet in that the magnetic field lines come out of the South Pole and enter into the North Pole. It is important to note that geographic north pole is not located in the same spot as the magnetic north pole. The Earth is actually spinning on it's axis at 11.5 degrees, as shown in the picture on the left, which aids scientists in determining paleolatitude.
    Paleomagnetism is defined as the "study of the terrestrial magnetic field as recorded by the magnetization of rocks during their formation" (Nicolas 196). Scientists were able to first conclude that the Earth's magnetic field reverses due to the alternating polarity found on either sides of the Mid-Atlantic Ocean Ridge. The picture sequence below helps illustrate this idea of Paleomagnetism. Since the Mid-Atlantic Ocean Ridge creates new ocean crust evenly on both sides of the ride, the magnetic polarity of the time at which the newly formed igneous rock cools is recorded (Nicolas 5). The recorded magnetic polarity then gives scientists a record of the paleomagnetism of the ocean floor.