
Figure 1.
Scaglia Rossa Limestone exposed near Furlo, Italy, in the Northern Apennine Mountains. Limestone at this locality accumulated on the bottom of a shallow sea, in an arm of the ancient Mediterranean ocean nearly 85 million years ago, during what is called Late Cretaceous time.
Despite this wandering of the crust, Earth' magnetic field is generated by electrical currents in the convecting liquid Ni-Fe metal of the outer core. On long time scales, the overlying wander of the mantle and crust does not affect the core, because those overlying rock layers are transparent to Earth's magnetic field. In contrast, the convection patterns in this outer core are actually forced to dance around Earth's rotation axis, which means that the overall pattern of Earth's magnetic field is predictable, spreading out in the same fashion as iron filings lining up over a small bar magnet. Hence, these data provide excellent information about the direction of the North and South geographic poles, and the tilt gives the distance from the poles (a vertical field means you are at the pole, horizontal tells us it was on the Equator). Many rocks actually record the direction of the local magnetic field as they form, in much the same way that a magnetic tape records your music. For example, tiny crystals of the mineral magnetite produced by some bacteria actually line up like tiny compass needles, and get trapped in the sediments when the rock solidifies. This, "fossil" magnetism can be used to track where the spin axis is wandering relative to the crust.














Comment: Clube's and Napier's hypothesis is being borne out by the worrying increase in fireball counts year-over-year. SOTT's Fire in the Sky section attests to that.