National Geographic has an interesting article describing the difference between a magnetic pole shift (which is what's happening now) and a physical pole shift:
Excerpt: "A physical pole shift, in contrast, would be triggered by uneven weight distribution in the Earth's interior or somewhere upon its surface, such as the formation of a giant volcano far from the equator. In theory, the force of the Earth's rotation would pull the heavy object away from the axis around which the planet spins. If that weight became sufficiently imbalanced, the Earth would tilt and rotate itself until the weight was redistributed near the equator. In the process, entire continents might shift from the tropics to the Arctic, at a rate far faster than the continents normally drift due to plate tectonics."
I remember a TV special years ago about a wooly mammoth that was found intact in the frozen tundra with buttercups in its mouth. Their theory was that the Earth had a sudden physical pole shift, which instantaneously transported the Wooly Mammoth from a tropical climate to the frozen tundra where it was flash frozen, preserving it (and the buttercups) for millenia.
Or it might have been Noah's Flood which occurred suddenly Very interesting hypothetical construct.
shalom b'SHEM Yah'shua HaMashiach
and from a tropical climate to one with a frigid climate.