[OldNavyVet]

From page 252 of “Darwin’s Ghost” by Steve Jones.

“The atlas of the past holds many surprises. To reconstruct it, all that is needed is to subtract from the map of today the ocean floor made since the date in question. The key is in the Earth’s magnetic field. Every few hundred thousand years, what was the North Pole becomes the South until the poles reverse once more in their endless dance. The switch is recorded in the rocks. Great stripes of magnetic reversal across the bottom of the ocean mark their movements.”

[Errant]

What could cause it to reverse? I understand the magnetic field is generated from the Earth's molten core rotating. It seems to me that this core itself might flip or somehow change poles through molten flows within the core.

Imagine if the core began wobbling, unbalanced, within the mantel. That should create some seismic activity!

Another thing, the Earth's precession occasionally has to catch up (there are charts/programs that demo this). This means that structures and bodies such as the mantel, core, oceans, Earth's crust, mountains, ice caps are affected differently by the inertial of the precession speeding up or slowing down. Imagine the disasters this could cause when/if this happens.

[Errant]

Here is a link to a video on Youtube that demonstrates the Earth's erratic spin precession though measured in thousands of years. If you watch long enough you will see relatively rapid changes in direction. These occurrences may be enough to cause traumatic cataclysms that could be related to events that cause polar shift or ice ages. My theory anyway...

Earth's Orbit Inclination Precession, Last 10 Myr