Congratulations, you found the end of the old terrain.
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"Strong Pokémon. Weak Pokémon. That is only the selfish perception of people. Truly skilled Trainers should try to win with the Pokémon they love best."
It's because the new 1.7.2 generation will immediately start a new section/biome whatever. It won't conjoin a similar layout. Happens every update.
Not entirely true, it only happens when the terrain generation algorithm changes, last time that happened was the inclusion of the jungle I believe. Since then and up to 1.6.4 all we saw was new items in chests or the spawning of new entities (chests in minecarts, horses...), nether quartz... Case in point I started my first world in 1.4.6 but there are no unnatural chunk borders until I cross into 1.7.2 territory.
Exactly my point, (a new) algorithm starts/changes whenever you cross previous update boundaries, i.e the point it generated up until.
Again, not entirely true, the algorithm doesn't radically change every update. If you started a world in 1.3 you will not be able to tell when you cross into 1.4.x, 1.5.x or 1.6.x chunks because there were no changes to the algorithm, the transition is seamless (unless data or computation corruption occurs) as if all chunks were generated in version 1.3. 1.7.x (or more precisely 13w36a) is the first update since the introduction of the jungle that changes the core generator, and thus, the same seed will start generating radically different results and show visible transitions on chunk edges.
However, anything before 1.7.2 had nothing similar in biome changes and therefore terrain generation as 1.7.2. So unless you build your worlds from scratch in 1.7.2; be ready for drastic transitions in your old worlds.
It's not a very pretty transition but it's gonna be cool for some of my projects.
Not entirely true, it only happens when the terrain generation algorithm changes, last time that happened was the inclusion of the jungle I believe. Since then and up to 1.6.4 all we saw was new items in chests or the spawning of new entities (chests in minecarts, horses...), nether quartz... Case in point I started my first world in 1.4.6 but there are no unnatural chunk borders until I cross into 1.7.2 territory.
Not every update do they change terrain generation.
Again, not entirely true, the algorithm doesn't radically change every update. If you started a world in 1.3 you will not be able to tell when you cross into 1.4.x, 1.5.x or 1.6.x chunks because there were no changes to the algorithm, the transition is seamless (unless data or computation corruption occurs) as if all chunks were generated in version 1.3. 1.7.x (or more precisely 13w36a) is the first update since the introduction of the jungle that changes the core generator, and thus, the same seed will start generating radically different results and show visible transitions on chunk edges.