Epic Land Corruption

I spawned into the first world of 1.5 and as soon as i spawned in the land generation was Crudded up. Biomes were in the place where they should not be. E.G One chunk of forest boime was in a mountain biome. E.G 2 huge ravine kinda between forest mountain and snow biome, also Birch tree was on a mount with snow on it.WAT IS THIS!!!!!