Now that Minecraft 1.2 has been released, I'm wondering how much of the new stuff added will ever appear in the world that I started playing in 1.1. Specifically, a new Jungle biome has been added, and the wiki page says this:
Jungles will only generate in chunks generated after 1.2.1.
I'm not sure how to interpret this. If I walk far enough in my world I started in 1.1 to a chunk I've never visited before, does it have a chance of being a Jungle biome? I guess what I'm generally asking is if the biome of a chunk is determined when the world is generated, or when the chunk is first visited?