Einstein wrote this letter to Charles Hutchins Hapgood. This professor in Antropology and History of Science was evolving a theory that could explain the dramatic climate-changes that, according to geological information, have taken place at nearly every spot on this planet.
These climate-changes appeared very sudden. According to Hapgood this could only be explained when the almost immovable Earth's outer-crust undergoes drastic shiftings. Those shiftings cause severe earthquakes, floods and drastic climate-changes.
Last time a pole-shift could have taken place was 11,600 years ago. Many species became extinct, especially great mammals, there was a big migration of people from North- to South-America and simultaneously agricultural experiments began all over the world.
Science accepts the theory of continental drift. The theory of polar-shift accepts this theory as well, but also assumes a more dramatic movement of the Earth's crust that can explain massal extinction, ice-ages and the sudden rise of agriculture.
Why would the poles shift?
The ice-caps grow and grow and collect more and more water from the oceans and the air. The rotation of the Earth causes a centrifugal force on northern- and southern ice-caps. This force gets bigger while the ice-caps get bigger. When the centrifugal force reaches a critical amount, the whole earth's crust will move. The poles will turn slightly toward the equator. Tropical zones will land at more temperate zones. Two spots on Earth now are the new poles; the cycle starts all over again.
Myths and old legends tell about catastrophes 'when the Sun came down', about great floods and about the survival of just a few men in boats landing on mountain-peaks pointing above the rosen sea-level.
Of course the Sun did not came down. The solar-system is too stable for that. But the theory of the pole-shifts coveres all those aspects myths talk about. The theory is convincing for it's simplicity.
The Roman poet Ovidius (43 B.C. - 18 A.D.) said to own a speech of Pythagoras. This great filosopher said to the people of Croton:
"I, considering the way generations came from the golden age to the iron age, am inclined to believe that the state of things won't be equal for long. I have seen the mainland change into sea and the creation of land out of an ocean... On mountain-tops old anchors were found."