Nice original idea but for once I agree with Illmaculate. There is no way that separate languages would form after even 100 years of separation. Teh survivors of the area would have spoken English and even if two communities had not met for 100 years they would still be able to understand each other. There would be different accents and different expressions starting but not a whole new language.

Please read about the evolution of language - it take a hell of a long time for one to develop.

Unless the "Gods" did it like in the Jewish Bible (old testament) and made us all speak other languages.