doc303, yes.. and the great plains were once the high seas. The earth has experienced many changes through the millions of years, billions actually. Something did happen in the recent past though. I'm sure too that human activity played no part until the last couple hundred years.
The current 'global warming' event is being enhanced, if not precipitated by human activity.
Here is an item of interest:
Ancient Flood Disrupted Ocean Circulation And Triggered Climate Cooling
Derach, your link had a problem. This one looks like what you intended:
EARTH CHANGES: Magnetic Field Reversal