If the volcano is exposed to the surface, on the world map it shows as a red ^, or whatever the character for a trap is for your tileset. Plus on the site finder, the volcano should be listed along with streams, rivers, etc.
Minor zombie problem. Embarked on a good/neutral/evil area, of course I plop down my fort right on the evil part. Thankfully the only thing it does is reanimate corpses. First 2 years go by without issue, a few dumb marksdwarves got killed by zombie giant mosquitos and bushtit men, but nothing bad.
Year 3, the elven traders managed to get into the depot, but just as they unload their
crap goods they detect a goblin ambush! I decide the only logical course of action is to close the drawbridge to the outside, sealing the elves and goblins in an airlock. Of course, now I have goblins trapped on my depot, and no cage traps or such to be rid of them yet. Thinking back, I totally forgot I could have just forged a few cages and called it good, thus preventing this disaster
Anyways, I stationed the marksdwarf squad on top of the main entrance, where I planned to put an archer tower, but hadn't gotten around to it. They shoot down the goblins while masons put up walls and carve them into fortifications, and work on sealing the roof. Another goblin ambush was spotted by a zombie elf head and was struck down by the marksdwarves. All of the sudden, giant crows show up, get shot down by the marksdwarves, and everything promptly zombifies and either flies or crawls up to the fort, and the crows go over the unfinished walls of the tower. Thankfully I had installed a hatch cover over the stairs, so after the crows died again i sent the marksdwarves back underground and sealed off the tower. Refuse hauling has been enabled on everyone, just to get these damned corpses underground into the temporary refuse pile, located in the non-reanimating side of the map.
Now to deal with the remaining goblin zombies, and clear up the surface a little bit. Shockingly, no one was injured in this whole mess.
EDIT: As soon as I unpause, human merchants show up, promptly see zombies everywhere and leave, and ANOTHER goblin ambush pops up and gets mauled by zombies. Damn it.