What is the basis of 2012 prediction?

There is speculation that the earths magnetic orientation will shift soon based on previous history, however no one today knows the answer. Sometime in the future your compass will read south when it is pointing north. This will affect the earths magnetic field, when it occurs. The Mayans never said that the earth would end, however they seemed to be a very advanced culture and when they made their calendar, they ended it on the year 2012. Also the prediction considers the solar storms that the sun produces every seven years. What could happen, but probably wont, is if the magnetic earth reverses at the same time as a sun storm, the rays will fry the earth because we will have no protection from the magnetic force field.

Hope that helps, but don't bank on this "theory."