From Karyn Wynn Fonstad's
The Atlas of Middle Earth has this info on
Thangorodrim:
..."the greatest of the
hills of the [hither] world. (This is from HOME4: The Shaping of Middle Earth I think)
..."the mightiest
towers of Middle-Earth." (From
The Silmarillion)
The central tower [of Thangorodrim] would...have to have been at least five miles in diameter at the base and some 35,000 feet high! (footnote: Mount Everest is 29,028 ft)
35,000 feet!!!!Imagine that eh?
Still I think that
Taniquetil and the Pelori were the highest
mountains in Arda.
Regarding other mountain chains:
The Misty Mountains: ...."as high as 12,000 feet."
The White Mountains: "There were probably some of the highest peaks in the known lands of Middle Earth (after the destruction of Thangorodrim and the Iron Mountains) - possibly even higher than those of the Alps."
..."for to have been snowcapped they must have been at least 9500 feet in elevation."
So the White Mountains are most likely higher than the Misty mts, therefore higher than 12,500 feet.
The Lonely Mountain: "The summit was high enough to be snowcapped at least as late as spring, and so was possibly 3500 feet in elevation."
Mountains of Mordor: "Around them the peaks rose high above, but were apparently lower than those of
the White and Misty Mountains. No mention was made of snow, although 'forgotten winters had gnawed and carved the sunless stone.' Still the peaks were probably quite high, for the top of the pass of
Cirith Ungol was more than 3000 feet above the Cross-roads."
"Mt.Doom....stood 4500 feet."
Ered Luin (in the
First Age, at any rate...probably this same info applies for the later
ages as well):
"The mountains were not snowcapped, and the
Elves had far less difficulty crossing them than, for example, they did the Misty Mountains."
Hope this helps. If I find any other info, I'll add it.
