This story contains major spoilers for Episodes 6 and 7 of “The Lord of the Rings: The Rings of Power.”
But one of the most thought-provoking scenes occurs when a volcano, which we learn is Mount Doom, erupts and creates the creepy wastelands of Mordor. The explosion was cinematically exciting, especially after a slow start to the season, which The Washington Post’s review described as beautiful, banal boredom. (Also, to point out the oliphaunt in the room: I liked “The Lord of the Rings” way before Jeff Bezos bought The Post and his company Amazon bought the rights.)
Volcano experts say many elements of the Mount Doom eruption are fairly realistic when compared with such explosions on Earth. But there are still a few details that can only be explained by elf magic, or more likely Hollywood effects.
“We really looked for a real-world way that you could do this instead of just kind of saying it was a magic thing,” said Gennifer Hutchison, a writer and executive producer on the series. “When you can do that, it’s always really gratifying.”
Here are five realistic — and not so realistic — elements of the eruption of Mount Doom and subsequent creation of Mordor, according to volcano experts.
Can water trigger a volcanic eruption?
The sequence of events begins when a henchman stabs a sword into a turnkey and unlocks a dam. The dam unleashes a powerful stream of water that flows through tunnels, which monsters called orcs have been building throughout the season (but you don’t know why until now — surprise!). The gush of water travels underground and sets off explosions throughout the village. Massive amounts of water then fall into the cavernous Mount Doom, triggering an apocalyptic eruption. Townspeople flee, homes are destroyed and the land burned into Mordor.
Water can help initiate a real-life volcanic explosion, said Mike Krawczynski, a geochemist at Washington University in St. Louis who studies what volcanoes are like before they erupt.
Krawczynski explained that groundwater in particular can come into contact with hot magma or hot rock and cause rapid boiling. The change in volume of liquid to gas increases the pressure. Pressure builds until the gases violently escape and explode. This steam-driven blast is called a phreatic eruption. Such eruptions are hard to predict because it’s difficult to forecast when groundwater may come into contact with hot rock or liquid magma.
There was, for example, a famous phreatic eruption on Mount Ontake in 2014, which killed dozens of hikers.
“It was like a geyser on steroids,” said Krawczynski of Mount Ontake. “So much pressure built up that it fragmented the rock. It threw rocks everywhere. It can create landslides.”
In the show, Krawczynski said that the steam explosions through the village mirrored phreatic eruptions on Earth. Rather than spewing hot-red lava, there were outbursts of steam and rocks that fell relatively close to the source.
But he questioned whether there was underground magma there that could rapidly vaporize the water and allow for the pressure to slowly build, both of which would be necessary for such an eruption.
Similarly, the cascading river into Mount Doom would likely not trigger the massive cinematic eruption.
“Adding surface water to a lava lake would create steam, but it cannot create the pressure necessary for an explosive eruption,” Krawczynski said. (Also, he said Mount Doom could never physically exist on Earth because no rocks are strong enough to support such a massive cavern, but we digress.)
Jeffrey Karson, a geologist and professor at Syracuse University, said an explosion could occur if there was no exit for the steam, and pressure builds.
The steam “can be very explosive and even blow rocks apart — but this would require some entrapment of the water that could be funneled and amplified in a bottleneck, like your thumb on a garden hose,” said Karson.
Would a volcano actually throw rocks and lava so far?
As Mount Doom trembled, a massive air-pressure wave shook the village. That’s very realistic. Sometimes, large volcanic explosions can create shock waves that people can feel and hear.
“It’s like a sonic boom to the extreme, and you feel it,” said Krawczynski. “It’s very sudden. It’s very loud. This happens.”
A recent real-life example occurred Jan. 15, 2022, when the Hunga Tonga-Hunga Ha’apai volcano in the South Pacific erupted. The volcano sent a shock wave around the world. The eruption was heard about 5,000 miles away in Alaska, while weather instruments also detected a change in pressure as the wave passed by.
Other aspects of the explosion are not as realistic, however. Volcanoes can eject rocks and lava material in the air called volcanic bombs, which can gash miniature craters in the earth. But huge chunks would not often travel as far as the show depicts.
Even a big eruption on Earth would not have enough energy to throw rocks that far. If it did, Krawczynski said the eruption would have destroyed the whole volcano and left a “big hole in the ground.”
Unlike the show, the most dangerous impact from a volcanic explosion is typically the ash, not the lava. Columns of ash get launched upward and then immediately ride the slopes of the volcano. This ash flow, called a pyroclastic flow, moves very fast — faster than a human (and maybe an elf) could run — and for miles.
The pyroclastic flows are ultimately what destroyed and buried the Roman city of Pompeii after the eruption of Mount Vesuvius in 79 A.D.
Could a volcanic explosion create Mordor?
Arguably, the most important scientific question of the scene is: Could such a volcanic explosion actually transform the plush lands of the Southlands into the barren lands where Sauron eventually lives? Probably not.
To obtain Mordor’s barren volcanic lands, you would probably need to cover a lot of the area with lava. But that probably wouldn’t be created by a volcano that looks like Mount Doom. Mount Doom appears to be an arc volcano, an explosive ash producer with thick lava that does not flow far.
Krawczynski said a Mordor-like landscape would require fluid lava, which is typically not explosive and would not create the ash flows or the steep-sided arc volcano seen in the show. Instead, such fluid lava would come from flat, shield-shaped volcanoes, such as those seen in Hawaii. And you would probably need more than one volcano.
“If you’re going to cover a large area with lava, you need really thin-running lava. You can’t have really thick peanut-butter-like lava,” said Krawczynski. “When you have thin, runny stuff, you don’t create steep slopes. You create vast planes.”
Krawczynski said if he were to write the geologic origin story of Mordor, it probably wouldn’t contain a volcano at all.
Around 1,800 miles below our feet in Earth’s mantle, hot, solid rock material is slowly but continuously rising and cooling — like a more complex lava lamp. Most hot plumes cool before reaching the surface, but particularly large ones can hit a tectonic plate, eventually leading to countless magma chambers and produce large-scale volcanism on the surface.
“If I was going to create Mordor, I would have a mantle plume come up,” said Krawczynski. “You could create this massive volcanic area [and] have fissure eruptions. No one would consider it one volcano because you’d have lots of different vents of lava going on everywhere.”
Krawczynski said such events have happened in Earth’s history, known as large igneous province events where “vast swaths of the Earth would be covered in lava, and would create barren landscapes, and have sulfuric-type gases seeping out.” One well-known example is the Columbia River Basalt Group, largely concentrated in Oregon and Washington. This flood basalt group was created around 6 to 17 million years ago when individual lava flows erupted through cracks in the crust and poured laterally, covering around 400 miles.
Of course, Krawczynski said he’s “getting into a lot of speculation” on Mordor creation theories. But in a way it’s the curse of knowing too much about geology while watching fantasy shows.
“When you’re a geologist, you know what to expect,” he said. “You know how those things were created.”