Survivors of the premature reformation of the supercontinent Pangaea tell their stories of the days after the disaster.

Who is the main character and what does he or she want?

This would make an interesting anthology movie, like Twilight Zone: The Movie.

Three stories about people who are linked in some way and their interaction telling a "fourth" story that encompasses the whole, like Pulp Fiction.

This sounds like a documentary or mocumentary. If it is a story it should be told through the eyes of a character. Listen to the last few "scriptnotes" podcast. It is really good and talks about how to tell big stories using characters.