Astrology/Astronomy in Middle earth?

[Cpt. Lundgren]

Most of those ideas seems to point at 10,000 BC, including ideas that an imbalance in the polar ice made the earth crust to shift, making an apocalytical disaster that almost wiped out the high-culture that they claim existed before (one of those ideas is that the remains of the civilisation is buried under the Antarctic ice). There are also a couple of buildings/structures around the world that those historians claim would make more sense 12,000 years ago (the ruin city in the Cambodian jungles,which I can't remember the name of but was used in the Tomb Raider movie, should be at the sea; some temple in South America would have something lined up with with the sun, etc). So it is those myths that I am drawing inspiration from. As I need a new reshape of Arda to to make the it look as our world, I am going with the more apocalyptical change instead of just rising the sea level.

As oral tradition has a tendency to mix things up, the destruction of Numenor and the reshaping of the world (that had the intention of destroying knowledge, as the main reason is to destroyed mans knowledge about magic) might have been combined into one story. Hence, the legend of Atlantis is born.

[Tobian]

Another thread you could follow is deep sea wrecks and ruins..

Because the polar ice caps melted, from their ice age size to their present (if shrinking even more thanks to global warming hehe) size, many of the sites exist off the coastal regions submerged, such as collossal Jumo stones off the coast of Nothern Japan, dozens of cities off the west coast of India (which were recently uncovered thanks to geophysics data), and there was a one in the pacific too..

These sites, like Numenor lie under the sea.. but unlike even the most powerful wizard in that age, we do posses the ability to travel to the bottom of the ocean.. could make for some intresting story arks, if one of your characters is a jaques Custeau style adventurer

[Cpt. Lundgren]

Didn't know about the ones on the coast of India. Sounds like I should read some more about them. There is also a site outside the coast of France that I am trying remember any information about. All I can remember at the moment is that it is some rows of stones I think there is a circle of stones as well. Not enough to search on...

About the final battle on Arda, I found this.
Dagor Dagorath, The Last Battle

The Dagor Dagorath, the great final battle at which the forces of the brothers Manwë and Melkor will face one another, and Arda will be unmade.

Notes
1 Actually, The Silmarillion never specifically states where the Last Battle will take place, though there is one hint. Akallabêth tells us that Ar-Pharazôn and his warriors are imprisoned in the Caves of the Forgotten 'until the Last Battle and the Day of Doom.' The fact that the Caves are located in Aman strongly suggests that the battle would have to take place there. This is apparently confirmed by several references in The History of Middle-earth that place the Last Battle in Valinor itself.

I will probably skip the "Arda will be unmade" part, but otherwise does it seems to be in line with the ideas so far

[Tobian]

Yes, there are several myths of sunken cities off the couast of India, even some encoded in the Vedas. The coastline in that area has changes quite a bit, even in living memory, meaning you can (allegedly) see the last city at low tide hehe. The recent surveys of the seabed were for an unrelated reason, but they uncovered large city like structures beneath layers of sediment. it has not been completelly confirmed they are actual cities YET, but the period when they could have existed (in most cases) is well before 10,000 odd years, so it's quite possible they could have been!

Arda being destroyed could well work quite well within the confines of your adventure actually... Don't forget that in most cultures apocolypse and 'the end of the world' is in reality a part of the cycle of rebirth, for example, in Inca and Maya myths (just because I have read a lot about them) the world they inhabited was actually the 5th such incarnation of the world, where the gods tried different solutions (of course eventually ariving at man ) to make the world. In botht he Aztec mythology there is some interpretation that when the Spanish invaded, they believed it to be the end of the world, and that Cortez was an incarnation of Quetzalcoatl, the winged serpent. In the Inca myths, also predicted using the relative constelations due to stellar drift (as mentioned before) they also believed it was the end of their age, and that the (then) king was to be the last one.. as it turns out they were right! But then that's the point.. maybe (in your paradigm) Arda did end, and it's death resulted in a rebirth, in the form of our world, hence it now looks completelly different... but as with the death of the Maya, Inca and Aztec peoples... part of their culture / people /artefacts and even whole cities still live on... Atlantis may be a Numenorian Machu Picchu, under the sea!

[Cpt. Lundgren]

Atlantis may be a Numenorian Machu Picchu, under the sea!

I like that idea. It could also have been under the control of the Black Numenorians, or another Numenorian group, and survived in some form to the end of the 4th age. That could make it a vital point of what is happening during the 4th age, and as an extension giving vital clues in the second campaign.