Minecraft wiki entry for Historical_effects, associated text: At excessive X/Z positions (depends on the operating system and version, but usually occurs between X/Z: ±268,435,456 and ±2,147,483,647, and early versions such as Beta), world render glitches out, resulting in terrain that appears to flicker. This does happen at X/Z: <±268,435,456, but it becomes very noticeable at X/Z: >±268,435,456 and gets worse every power of 2 beyond that. This could most likely be that past X/Z: ±268,435,456 the Minecraft world is 32 blocks off, which is as large as 2 chunks, though it is unconfirmed.