My friend generated a world wich was super glitchy. Some chunks were completely high and watery, the most of the world was at cloud level, random floating sand, and other crap. We had some problems with floods, but they got fixed now.
this is the 9000th post in this part of the forum!!!
I heard charged creepers have bigger explosions than normal ones. And the lava - id bet there was a lava stream in that mountain. It can occur sometimes with some world seeds. Search "minecraft seed generator fail" on youtube
Saw a pic on the wiki, a charged one should be glowing.