Palaeomagnetism in the crust is represented by the declination of iron oxide minerals in the solidified lava, during cooling these will freeze to record the direction of magnetism through time. The declination is set at the Curie point during cooling (around 550 degrees centigrade).

The direction of the poles at that point is therefore laid in the rock as a fossil, and can be seen as a series of bands on the sea-floor indicating present and inverted magnetism.

As the poles reverse again the characteristic banding forms.

The sea-floor profile therefore looks like the one bellow.

Composed by Rob Jacobs
© 1997