Just out of idle curiosity, what exactly is it that you think explains the frozen mastodons? I'll grant you that the verse about Shem's heirs dividing up land somehow refers to plate tectonics. Sure, whatever. But what mental acrobatics take you from there to the frozen mastodons, and how does that segue in with magnetic pole reversals?
That's what I was taught in school science class. I don't have a better theory so it sounds fine to me. A quick "Google" on pole movement should reveal the north pole is moving as we speak and getting weaker. The animals were frozen standing up with fresh food in their bellies. In order to do that, they would have to be almost flash frozen. If it took longer than a day or so, they food would have wilted and they most likely would have laid down like most other animals to die.
The truth is we don't know ANYTHING about what happened in the past because we weren't there. Theories are just that, theory. Most theories on FreeRepublic today have anomalies, or things the theory can't explain. They are believed on FAITH. What I know is something drastic happened, but the cause is up for grabs. People that say they KNOW are liars. There have been many Discovery TV type shows on pole reversal, so it's as good as any to me.
Let's just say for instance the animal was eating his dinner on a spring day about the latitude of Vermont. All of the sudden, within hours he is at the latitude of the Arctic Circle. Nobody has talked about the size of the dung heap behind him buried in the ice, but I'm sure it would have been a wild ride.
Some Google results for "magnetic pole reversal"
http://www.pureenergysystems.com/news/2005/02/27/6900064_Magnet_Pole_Shift/
http://www.pbs.org/wgbh/nova/magnetic/reversals.html
http://www.indiadaily.com/editorial/1753.asp
http://en.wikipedia.org/wiki/Earth's_magnetic_field
There are tons more, but that will get you started.