Minecraft crash

while playing on the "cave madness" custom map preset, Minecraft suddenly crashed. When I try to re-load the world, it crashed again after about one click. I do not understand the error report the launcher gave me, so I'll post the entire thing here. It's incredibly long, and i'd cut unnecessary fluff if I could, but I don't want to exclude anything important. I think it said something about block updates, but other than that, I'm not sure.