...prophecies of end of world disasters? I remember a series of books (maybe a trilogy?) about prophecies of huge natural disasters at the end of the world and relating to mormonism
Are you talking about Cleon Skousen's thousand year books? They are "The First Two Thousand Years", 'The Third Thousand Years', and 'The Fourth Thousand Years.'
But the only one that would talk about the end of the world would be the last one.