The Rings of Power revealed the origins of Mount Doom
That is, indeed, Mount Doom.
Mount Doom, the volcano in the heart of Sauron’s wicked domain of Mordor, is possibly the most renowned mountain in Middle-earth, from the heights of the Misty Mountains to Erebor. We received a startling and spectacular origin tale for the series’ most renowned volcano in the newest episode of Amazon’s The Lord of the Rings: The Rings of Power.
[Editor’s note: This tale includes spoilers for The Lord of the Rings: The Rings of Power, episode 6].
To begin with the most apparent question, yes, Mount Doom did erupt at the end of the episode. If, like Galadriel, you have trouble recalling what Middle-earth looks like on a map, the Southlands of The Rings of Power, where the besieged settlement of Ostirith is located, is also the territory that will eventually become Mordor.
The evolution of the land from lush fields to beautiful mountains appears to have been part of a grand design by Morgoth or Sauron, and was triggered by the sword-key, releasing a massive flood. This flood destroyed the land, thanks to the tunnels dug by the orcs, and triggered an eruption of the volcanic Mount Doom (though it doesn’t have that name yet in the show’s time) until it erupted. This eruption spewed molten rock and magma in such a wide radius that it appears to have scorched the area forever, or at least until Frodo, Sam, and Gollum arrived with the One Ring.
While the history of Mount Doom isn’t very explicit in Tolkien’s lore, the show’s story does seem to mostly line up. We know that the land wasn’t always called Mordor, and that the name likely arrived after Mount Doom’s eruption, but there’s no mention of the eruption itself being caused by an intentional flood.
As for what will happen to the area next, and how long it will take before Sauron takes up residence there, we’ll just have to wait to see where The Rings of Power takes its story next.