As can clearly be seen by this image

http://i.imgur.com/NgKsLSr.jpg

the nuke at the beginning of the game did NOT hit where the Glowing Sea is, but, in fact, hit at the Cambridge Crater area.

So, if that nuke didn't cause it..... what did?

If that fell at Cambridge, than it is another nuke I guess. Or maybe something near that Nuke-launching site blew up.

My guess would be a nuke hitting where we had missiles stored and ready to launch in the Glowing sea area. The crator of atom to be precise.

there is... Was a nuclear reactor in the glowing sea that melted down right after the bombs hit. It is a big [censored] crater though.

There is a terminal in an unmarked "factory". In it the foreman talks about his new job and such. The last entry in his personal log states, The Day After (which was also a cheesy 80's TV movie about the US being nuked, though cheesy, it was scary). Anyways part of the entry says:

" I was sleeping in my chair when it happened. They must have missed the city with the big one - Framingham's gone from what little I heard on the radio before it went quiet".

Framingham is right next to Natick. Now I know the Fallout map is not to scale or that accurate. The crater is south of Natick and Framingham is west of it, but we know there is alot of inaccuracies in the game.

Maybe we didn't see the big one go off, we probably saw Cambridge go off and the vault elevator descended before we saw any more.

Another nuke would be my guess. The glowing sea seem to be a place where missiles and nukes where stored prewar so tha area being hit by a nuke could have created it.

The (Real) Soviet Czar Bomb if fully armed would be 100 megatons. Something like that could have smashed into the glowing sea.

Most likely. If "the big one" hit Cambridge I doubt it would look as good as it does. The city would also be much worse. Going off of what we know about Yangtze. I would say that is probably what hit Cambridge. Though using the nukes that the Captain lets you call in they are pretty lackluster.

The explosion is more south of V111 than east. I've checked it on the map while playing and that's what I'm seeing in the picture. The glowing sea is south of V111. It looks like it is hitting closer to the eastern edge of the glowing sea to me (like where the plane went down) than it does true south where the crater of atom is, but it isn't so far east that I'd think it went down in Cambridge.

The load-screen snippets state that the glowing sea is the impact site of:

"The high-yield warhead that devastated much of Massachusets".

This suggests a single, czar-type bomb. Whatever caused Cambridge crater could have happened at any time over the 210 years since. There's been plenty of warfare and fighting in that time.

The bomb in the intro goes off DUE SOUTH of v111, just played it to verify (get yourself facing due south before the compass vanishes, bomb goes off dead center). The Crater of Atom is pretty much due South of v111 as well. Case Closed, as far as I'm concerned.

This. With MAD, you don't fire off one nuke and be done with it. You launch your entire stockpile. And if nuke numbers were anything like they were in the Cold War (likely even more), then they have nukes to spare to ensure a location has been irradiated to hell and back.

Dirty Fev Nuke From Vault-Tec.

That, and the area surrounding the Boston City crater(s) are still too unaffected to have been the big one.

Like crunch1200 said, the Glowing Sea is probably ground zero of the Commonwealth attack.

I'm gonna go with the wrecked nuclear reactor site that we an find half-buried out there. It would've likely scarred the region worse than the nukes ever did.

I'm pretty sure that bomb hit where the Glowing Sea is. I checked and as I remember I was facing due south on the compass as I was looking at the bomb going off. Where we see the mushroom cloud is where we see that persistent Glow from the Crater of Atom, which you can see at night from almost anywhere on the map.

That wrecked reactor might be the reason the Glowing Sea is still so thickly irradiated, though. The Capital Wasteland got hit with a ton of nukes, and if the Commonwealth is 0 and the Glowing Sea is 10 on a scale of green irradiatedness, the Capital Wasteland is maybe a 4. A longterm, unattended nuclear meltdown compounded with nuclear fallout from the bomb may be what keeps the place looking so green and fresh.