[SunkenCiv]

This graphic shows the tilting of the Earth that might occur if a dramatic imbalance in the planet's mass distribution ever developed in the Arctic. According to the theory of true polar wander, a heavy spot in the Arctic -- caused by a very large upwelling of magma, for instance -- would reorient the planet over 5 to 20 million years so that the heavy spot would lie at the equator, changing the orientation of the Earth in relation to its poles. New evidence uncovered by the team of Princeton geoscientist Adam Maloof shows that this sort of reorientation may have occurred in the planet's distant past. (Graphic: Maloof Laboratory)

[muawiyah]

Part of the idea is that hot plumes of lighter material from the mantle drift up and cause the mass balance of the Earth to change ~ sometimes dramatically.

Interestingly enough such a plume appears to have cut right through the Juan de Fuca plate under Oregon and appears to the East as Yellowstone.

On a far smaller scale the fact that Florida arches up from the Caribbean is that the magma under the crust flowed South under Florida as two miles of Ice pressed in at the North. This leaves Florida high above sea level during the short Interglacials, and possibly well below sea level during the periods of glaciation (which cuts off the Gulf Stream entirely for 100000 years.)

This has presumably happened 20+ times since the onset of the most recent period of glaciation.

This can also account for the existence of the Mississippi Valley as we see it today. Not too long ago it was a long arm of the Gulf of Mexico reaching up all the way to what is now the Ohio River. There are even sandy beaches left in unglaciated parts of Southern Indiana! They used to be on the Gulf. This is nice, fine sand too.

[SunkenCiv]

This graphic shows the tilting of the Earth that might occur if a dramatic imbalance in the planet's mass distribution ever developed in the Arctic. According to the theory of true polar wander, a heavy spot in the Arctic -- caused by a very large upwelling of magma, for instance -- would reorient the planet over 5 to 20 million years so that the heavy spot would lie at the equator, changing the orientation of the Earth in relation to its poles. New evidence uncovered by the team of Princeton geoscientist Adam Maloof shows that this sort of reorientation may have occurred in the planet's distant past. (Graphic: Maloof Laboratory)