The everlasting, undying question: Why does the world map of Hyrule change with each game?
Obviously, being stuck with the same world map would make changes to the gameplay far more difficult. Imagine implementing Z5 with the map from Z1; it’s way too hard. However, the names, characters, races, and so forth are mostly consistent throughout the games in name and specification. Alot of theories have been presented; the Zelda HQ has created its own timeline which disregards the geographic changes, and can be found here. How the world changes – and how the species of Hyrule have changed – is a mostly unknown process. Since the forces that act upon Hyrule are far different from those on Earth, it could be any number of reasons. Geographical changes that would take millennia on Earth could very likely occur within a century in Hyrule.
