Can the Earth Crust Slip?

This fascinating post can be found at http://chiefio.wordpress.com/2011/01/22/can-the-earth-crust-slip/ the blog of EM Smith, 'Musings from the Chiefio' and posted on January 22nd. He ponders for awhile on whether the crust of the earth might slip and therefore create 'Pole Shift' – presumably along the lines of Hapgood. He doesn't reach a conclusion, as he generally does not in any of his posts, but is instead thinking aloud – and thinking what many regard as impossible. The idea of crustal slippage is never really discussed in public science, so Joe Public is not really aware of any doubts that may exist. Here we have ten pages of serious comments from visitors to his site. It has no banal commenters and such never seem to appear as posters. I assume their comments are liquidated somewhere in the process of uploading the daily intake. Hence, you will find the discussion quite useful – and may even add to it. As Smith muses, a solid core, a gooey mantle topped by a thin crust with an 'inviscid' layer of convecting material between might be moved by a thump from a suitably sized cosmic object that could set the crust wandering for awhile. What interested me the most was the possibility of wobble. Science currently understands the Chandler Wobble by modern dynamics – and not by what might have happened in the past. Is it possible wobble might have existed for years, or centuries, and how might wobble on such a timescale be discernible in the ice core record (or any other proxy dating methodology). How would wobble be revealed during the Ice Age for example?