What is the relationship between the locale mapped in the Silmarillion and the locale mapped in the LOTR books?
As a kid I always assumed the Silmarillion map was of a place somewhere on or overlapping the LOTR map, but changed due to land shifts both natural and supernatural.
But I was wrong, wasn’t I?
-FrL-
All of Beleriand except a few extremely eastern bits were sunk under the sea.
Ah.
I only read about half the thing. 
-FrL-
See those mountains towards the east? Those (somewhat) become the Ered Luin (Blue Mountains) of the Third Age. Ossiriand is to their west.
And the March of Maedhros had a hill (Himring) which you can find in the top left portion of the map of Middle Earth - northwest of Lindon.
Its amazing that Tolkien did the Atlantis thing twice – Beleriand and Numenor.
Except Beleriand wasn’t Atlantis because it was connected.
Numenor is the closer analogy.
Indeed, Beleriand would be better analogized by Lyonesse or the city of Ys, than by Atlantis.
Plus, Númenor was actually intended by Tolkien to be Atlantis.
If you start at the Shire and head west, you come to the Tower Hills, then the Blue Mountains. Keep going west to northwest, and you head out over the ocean. This is Beleriand. It was sunk under the waves when the Valar answered Earendil’s plea and came to defeat Morgoth. The clash of the Powers was too much for the land.
Oh, come now, DSYoungEsq and Lightray – there’s no similarity between drowning a landscape like Beleriand and Atlantis? I agree, Numenor is the acme of Atlantis-ism, but come on.
As Lightray noted, Lyonesse is a better analog for Beleriand, as a drowned land connected to a still existing continent. Tolkien definitely made Numenor his Atlantis analog.
Check out Fonstad’s “Atlas of Middle Earth” sometime to get a good map representation of the relationships between Valinor, Avalonnë, Beleriand, Eriador, Rhovanion, Numenor (Atalantë), and so forth.
Númenor wasn’t just the acme of Atlantism – it was Atlantis. That was Tolkien’s intent. That is why the drowning of Númenor matches one of the common themes of the drowning of Atlantis – the hubris of its inhabitants.
Beleriand, on the other hand, was not drowned for the hubris of its inhabitants. It went under because the gods (Valar & Maiar) fought thereon. They broke it, not really on purpose, but because they were ending the dominion of Morgoth, whose house was there. The civilization of Beleriand, however, survived.
Thematically, that is not like Atlantis (whose civilization perished, as with Númenor). It is more similar to Lyonesse, where Tristam died, and the land sank, except for the people who survived.
Not that I think Tolkien was going for similarity to Lyonesse. The sinking of Beleriand echoes the breaking of Arda, from the last time the Valar fought Morgoth. He wasn’t repeating the Atlantis theme.
And, in what I’ve always thought of as an excellently light touch of pathos, Tol Morwen.
The island on which Numenor was placed after the downfall of Beleriand was originally called Elenna, “Starwards.” But after the Drowning of Numenor, it was called “the Downfallen,” or Atalante in Sindarin.
“Lyonnesse? You mean the legendary land west of Cornwall that was engulfed by the Sea? That’s a scilly idea!”
That’s Atalantë, and it’s Quenya.
Thanks for the correction, Q.
Essentially, Beleriand was a term for both (a) all lands in Middle-Earth west of the Blue Mountains (Ered Luin) and (b) that large crescent-shaped area south of Hithlum and Doriath and west of the River Gelion – comprising that part of (a) that excludes Morgoth/orc-dominated areas, Hithlum, Doriath, and Ossiriand. Ossiriand was the area between Gelion (to the west) and the Blue Mountains (to the east).
All Beleriand was submerged in the battles at the end of the first age except the two islands (former hills) mentioned (Himling/Himring and Tol Morwen) and the northeast piedmont of Ossiriand, which became Lindon (divided by the Gulf of Lune into the Harlond and the Forlond), the site of Mithlond, the Grey Havens. Lindon was the last Noldorin kingdom, until the fall of Ereinion Gil-Galad in the wars against Sauron, after which it was governed by Cirdon Shipwright. So a few small pieces of Beleriand that had not come under the thumb of Morgoth survived the downfall.
grabs a herring
SMACK!
I am always happy to badger someone pitilessly over a meaningless point, Poly! 
Oh, and the “scilly” thing was a work of art!