What's the tallest mountain in Middle-earth?

Question

There are many mountains in Middle-earth, from the harsh Misty Mountains to the humble Lonely Mountain. This made me wonder, what's the tallest mountain in:

• Middle-earth,

• Arda (Tolkien's Universe)?

The tallest mountain in Middle-earth might not be the tallest in the entire Legendarium, which is why I have extended the question to include Arda as a whole. For example we have Menelterma which is the highest mountain on Númenor. Is this taller than Middle-earth's highest mountain?

What are the tallest mountains in Middle-earth and Arda?

Answer 1

Middle-earth

In Middle-earth throughout all time it is almost certainly Thangorodrim:

And looking out from the slopes of Ered Wethrin with his last sight he beheld far off the peaks of Thangorodrim, mightiest of the towers of Middle-earth...
_{The Silmarillion, Chapter 13: The Return of the Noldor}

In this case "towers" almost certainly means mountains. Morgoth almost certainly raised them in opposition to the great Taniquetil, home of Manwë.

There is no indication of what was the tallest mountain in the Third Age but of those listed below, I would hazard to guess that the Mountains of Moria, and therefore Caradhras, were the tallest based purely on the fact that the Great Eagles had their Eyries in those mountains and I could only imagine the servants of Manwë choosing the loftiest peaks (although they were located on Celebdil not Caradhras).

Arda

The aforementioned Taniquetil is the tallest mountain in Arda and is so described in the Silmarillion:

Manwë and Varda are seldom parted, and they remain in Valinor. Their halls are above the everlasting snow, upon Oiolossë, the uttermost tower of Taniquetil, tallest of all the mountains upon Earth.
_{The Valaquenta}

Notable mentions:

Other notable mentions in Middle-earth (and Númenor) include the Crissaegrim peaks, the Meneltarma, Orodruin, Erebor and Caradhras

The Crissaegrim peaks were the location of the Eyries of Thorondor the Greatest Eagle:

[Húrin] descried far off amid the clouds the peaks of the Crissaegrim ... Then Húrin looked up to the grey sky, thinking that he might once more descry the eagles, as he had done long ago in his youth; but he saw only ... clouds swirling about the inaccessible peaks, and he heard only the wind hissing over the stones.
_{The Silmarillion, Chapter 22: Of the Ruin of Doriath}

The Meneltarma, the Pillar of Heaven, reigned supreme on the star-shaped isle of Númenor. While a specific height is not given the tower is often described as being of a great height, tall enough that the exiled Faithful would sail out in search of it's tip that was storied to still poke out of the sea as an island.

in the midst of the land was a mountain tall and steep, and it was named the Meneltarma, the Pillar of Heaven, and upon it was a high place that was hallowed to Eru Ilúvatar
_{The Akallabêth}

Among the Exiles many believed that the summit of the Meneltarma ... was not drowned for ever, but rose again above the waves, a lonely island lost in the great waters; for it had been a hallowed place, and even in the days of Sauron none had defiled it.
_ibid.

Orodruin, Mount Doom:

Still far away, forty miles at least, they saw Mount Doom, its feet founded in ashen ruin, its huge cone rising to a great height, where its reeking head was swathed in cloud.
_{Return of the King, Book VI, Chapter 2: The Land of Shadow}

Erebor:

... and now they could all see the Lonely Mountain towering grim and tall before them.
_{The Hobbit, Chapter XI: On the Doorstep}

And last but not least, Caradhras. While there's speculation that Celebdil might have been taller as that is where the Eagles' Eyries could be found, Caradhras seems to be the clear winner according to the Lord of the Rings:

At the left of this high range rose three peaks; the tallest and nearest stood up like a tooth tipped with snow; its great, bare, northern precipice was still largely in the shadow, but where the sunlight slanted upon it, it glowed red.
_{Fellowship of the Ring, Book II, Chapter 3: The Ring Goes South}

And later in the same chapter:

On the third morning Caradhras rose before them, a mighty peak, tipped with snow like silver, but with sheer naked sides, dull red as if stained with blood.
_ibid.

While no heights are ever really given for the mountains, and idea of the height of Caradhras can be gathered from this answer on the height of the structure of the stairs and this answer about how big Khazad Dûm was.

Answer 2

In all probability, the two tallest mountains in the history of Middle-earth (and, in fact, all of Arda) were the two pillars* Helkar in the North and Ringil in the South. These were built by the Valar to hold to the two lamps—Illuin and Ormal, respectively—that illuminated the Spring of Arda. The pillars reached up to the stars in the sky, and their destruction by Melkor at the beginning of the Battle of the Powers caused the creation of two new seas and they crashed down to earth.

*As with the later towers of Thangorodrim, which stood over Angband, I don’t think there is a meaningful difference between mean a “mountain” and a “tower or pillar fashioned by (semi)-divine hands.”

Answer 3

As far as I know, only one mountain in all of Middle-Earth or even all Arda, had a specific elevation from base to top mentioned.

The Return of the King, Book VI, Chapter 3, "Mount Doom", when Sam has carried Frodo part way up Mount Doom:

The Mountain standing ominous and alone had looked taller than it was. Sam saw now that it was less lofty than the high passes of the Ephel Duath which he and Frodo had scaled. The confused and tumbled shoulders of its great base rose for maybe three thousand feet above the plain, and above them was reared half as high again its tall central cone, like a vast ost or chimney capped with a jagged crater. But already Sam was more than halfway up the base, and the plain of Gorgoroth was dim below him, wrapped in fume and shadow.

Of course the relative and absolute dimensions of Mount Doom are not exact, since the base rose for "maybe three thosuand feet" and not for an exact figure, and the central cone was probably not precisely "half as high again" as the base. So obviously the actual height of Mount Doom at that moment could easily be several percentage points higher or lower than calculated from that statement.

But the big problem is with the cone being half as high again as the base. That can be interpreted two ways.

One) the height of the cone is about half that of the 3,000-foot-high base, again", and thus about 1,500 feet, thus making the total height of the mountain "half as high again" as the base, or 4,500 feet total.

or:

Two) the height of the cone itself is "half as high again" as the 3,000-foot-high base, or 4,500 feet, which added to the 3,000-foot-high base, makes the total height of Mount Doom 7,5000 feet.

So at that time the crater at the top of Mount Doom should be either about 4,500 feet or about 7,500 feet above the plain.

So the passes of the Ephel Duath mountains should be higher by an unstated amount than 4,500 feet, or 7,500 feet, and the peaks should be much higher than the passes.

In The Silmarillion, the Quenta Silmarillion, Chapter III, "Of the Coming of the Elves and the Captivity of Melkor" Orome leads the Elves westward through Middle-earth on the Great Journey:

And it came to pass after many years of journeying in this manner that the Eldar took their course thorugh a forest, and they came to a great river, wider than any they had yet seen, and beyond them were mountains whose sharp horns seemed to pierce the realm of the stars. This river, it is said, was even the river which was afterwards called Anduin the Great, and was ever the frontier of the west-lands of Middle-Earth. But the mountains were the Hithaeglir, the Towers of Mist upon the borders of Eriador; yet they were taller and more terrible in those days, and were reared by Melkor to hinder the riding of Orome.

I thought that quotation said that the Misty Mountains were the highest mountain range in Middle-earth, but it doesn't. But it does say that the absolute heights of the Misty Mountains and no doubt other mountains, and thus their relative height rankings, changed in various convulsions of the earth between the Eldar days and the composing of the Quenta Silmarillion.

So the tallest mountains in Middle-Earth did change from age to age.

Answer 4

The highest mountain on the entire planet since the Change of the World, i.e. in the 3rd and 4th age and without Aman, is the Kalormë on the continent east of Middle-earth, the Lands of the Sun. Kalormë

It was the 2nd-tallest mountain on the plane of Arda before the Change of the World, and seems to have been the antipode of the Taniquetil on Aman which was the highest mountain and the only one that reached into Ilmen (outer space). The antipode of the Taniquetil, I guess Kalormë's elevation may be half that of the exceptional holy Taniquetil, so if the Taniquetil were ~60,000 ft in elevation (Armstrong limit) Kalormë would be about half as high and thus similar in elevation to Mount Everest.

The highest mountain on the continent of Middle-earth is, as an above answer has said, the Caradhras (Redhorn), and in the 1st age the Thangorodrim around 35,000 ft in elevation. I estimate Caradhras' elevation as similar to the Monte Bianco, about 16,000 ft. However, the Celebdil, the Fanuidhol, the Erebor and the Ered Nimrais may be only slightly lower.