What caused the Doom of Valyria: A geological analysis

They say the Doom still rules Valyria. The maesters tell us of a city destroyed, of mountains exploding, and of ash clouding the skies. The geologists tell us of something much more terrifying.

Interpreted geological features surrounding Valyria.

When trying to determine the cause of the Doom of Valyria, we must begin with what we know for certain. We know the volcanic mountain chain known as the Fourteen Flames played a part. We know the ground shook. We know that the sea rushed to far shores and swallowed everything in its path. And citizens of Westeros and Essos alike still speak of the vast Valyrian peninsula shattered into countless islands. Fortunately for us, we can use the tools of the geologist to uncover what really happened to Valyria nearly 400 years ago.

The Doom would have begun with a rumble. The Fourteen Flames ran West to East across the Valyrian peninsula, indicating that a large fault and subduction zone exists to the south. This is consistent with the documented spreading center within the Narrow Sea if it continued to the southeast once it passed the southern tip of Westeros. In tectonic settings such as this, earthquakes and volcanic eruptions can often be found together. In the buildup to the first catastrophic eruptions, magma from deep within the Earth would have swelled up and the immense pressure would have generated tremors that could be felt for miles. The eruptions would have started soon thereafter.

Whether it were months, weeks, or days, the citizens of Valyria might not have taken particular notice that the ground trembled beneath their feet. After all, they had built their city in a tectonically and seismically active area. Small tremors would have been commonplace. The first hint that something extraordinary was happening would probably have been a deafening roar to the East.

Lithograph of Krakatoa (or Krakatau) eruption, 1883

The texts tell us that “on the day of the Doom every hill for five hundred miles had split asunder to fill the air with ash and smoke and fire.” This is probably hyperbole, but it indicates that a single volcanic eruption isn’t the culprit — it must have been a series of eruptions. On Earth, there are few examples of something like this occurring. When it has happened, the erupting volcanoes were actually a part of the same volcano complex, yet the scale and distance between the Fourteen Flames makes this situation unlikely. But if we stretch the laws of Earth physics just a little, we can generate a series of eruptions like those described in the old poems of the Doom.

The first eruption would have been marked by a tremendous explosion some 200 miles East of Valyria. Poems about the Doom quoted by Tyrion Lannister clearly state that the “hills split asunder” and that “the waves, the sea whipped and churned” before the city-proper was destroyed. This strongly suggests that the Doom didn’t begin in Valyria itself, but rather, began somewhere closer to shore. We also know that “a wall of water three hundred feet high had descended upon [the Isle of Cedars]” in the sea to the northeast of Valyria while the city of Volantis, to the northwest, was spared the same fate. These details suggest that the Doom began with a volcanic eruption near Slaver’s Bay similar to the 1883 Krakatoa eruption on Earth.

The Krakatoa eruption generated a tsunami over 130 ft. tall and produced the loudest sound in recorded history. The explosion was so violent that it tore the island apart and left a 2.5-3 mile wide (4-5 km) caldera behind — effectively, a collapsed hole in the Earth’s crust (texts of the Doom state, “the ground splintered and collapsed and fell in on itself,” which is a pretty accurate description of caldera formation). Sailors nearly 50 miles away wrote of the eruption, “I am convinced that the Day of Judgement has come.” This sounds appropriate for the Doom.

So, assuming the Doom began with such an eruption, citizens in Volantis, over 2,600 miles away, would have heard the explosion as the distant roar of cannon fire (or, because cannons do not exist in Essos nor Westeros, perhaps the roar of barrels of wildfire detonating). Citizens of Meereen, nearly 2,000 miles away, would have heard the eruption as a series of loud artillery blasts. Citizens of Astapor, nearly 1,100 miles away, would have described the sound as extraordinary guns. And citizens of Valyria would have experienced something that physicist (read: Earth maester) Aatish Bhatia described as, “so astonishingly loud that it’s inching up against the limits of what we mean by ‘sound’.” And this was just the beginning.

Landslide on Mt. St. Helens, 1980. Fun fact: it’s the largest landslide in recorded history (and “fun” is relative).

The tremendous blast of the Krakatoa-like eruption to the East of Valyria would have shook the Earth. This may have triggered a catastrophic landslide on a different volcano to the West. Similar to what happened at Mt. St. Helens on Earth in 1980, the landslide could have suddenly released the tremendous pressure built within a subterranean magma chamber and triggered another eruption. If this volcano’s magma chamber were linked to yet more volcanoes via a system of underground sills and dikes then those volcanoes, part of larger volcanic complex, might have erupted as well. These volcanoes might have triggered more earthquakes, which might have triggered more landslides in a domino effect across the Valyrian peninsula. Perhaps bad timing would have brought other explosive eruptions like Krakatoa as well; some might have even been 10-100 times larger, similar to the Tambora and Toba eruptions on Earth, and would have devastated the surrounding areas. Somewhere near the middle would have sat the volcano that destroyed the city of Valyria.

The ruins of Old Valyria. One might ask how they became so well exposed following their burial beneath a pyroclastic flow. But then again, one might ask a lot of things.

The ruins of Valyria share many similarities with the ruins of Pompeii and Herculaneum on Earth, suggesting that a similar fate must have befallen Valyria. Both Pompeii and Herculaneum were destroyed, buried, and preserved during the eruption of Mt. Vesuvius. Scalding hot clouds of superheated air and ash, called pyroclastic flows, overran the cities and buried the buildings and citizens in a matter of seconds. Later, those deposits would cool into a low(ish) density rock, called tephra, that eerily preserved the cities until they were later dug up by archaeologists. Such an eruption was considerably smaller than a Krakatoa-like eruption — nearly 10 times smaller — but the devastation would have been enough to convince anyone that the world was ending. One witness to the Vesuvius eruption wrote, “Many besought the aid of the gods, but still more imagined there were no gods left, and that the universe was plunged into eternal darkness for evermore.”

And at last we reach the final, and most controversial, detail of the Doom of Valyria. It is mentioned frequently in the retellings, but is strangely absent from any primary text. It is the cataclysm that fractured the Valyrian peninsula into countless smaller islands and created the Smoking Sea. Indeed, even the Mother of Dragons herself, Daenerys Targaryen, recalls looking upon a tapestry of Old Valyria and noting, “There is no Smoking Sea… Valyria is not yet an island.” It is here where we must relax the tight constraints of oral traditions about the Doom (stories of islands have been grossly exaggerated before) and rely more wholly on the geological sciences to determine what, exactly, fractured the peninsula — and when.

Yellowstone caldera, one of the largest on Earth, doesn’t even come close to being big enough to split Valyria.

While violent volcanic eruptions, such as Krakatoa, can destroy parts of islands, they could not realistically destroy enough land to fracture the massive Valyrian peninsula. The Valyrian peninsula is approximately 500 miles wide and 700 miles long. The volcanic crater — better known as a caldera — created by the Krakatoa eruption on Earth was just 2.5-3 miles across. The largest volcanic calderas on Earth are around 35-60 miles across (Yellowstone, La Garita, and Toba). To truly fracture the Valyrian peninsula into its current form would require a series of hundreds to thousands of volcanoes. And I’m not willing to stretch physics that much. Likewise, we can’t split the peninsula with a spreading ridge because the required spreading rates would be far too large (20,000-40,000 cm/yr as opposed to 13 cm/yr on Earth). But we can come up with a different solution.

There does exist a force large enough to fracture a significant portion of the Valyrian peninsula, but it doesn’t come from deep within the planet. It comes from outer space: a meteor. And there is circumstantial evidence that a meteor struck the Valyrian peninsula at some point millions of years ago.

1) The size of the Smoking Sea. While volcanic eruptions can’t create a series of calderas large enough to create the Smoking Sea, a meteor impact might. The largest impact crater still present on Earth’s surface is in South Africa, and it’s 186 miles across. A (mostly) circular impact crater of this size would fit nicely in the Smoking Sea, and the central peak (created by the rebounding of the crater floor) might even explain the presence of one of the “islands.”

Cross-section across Vredefort crater, the largest (and apparently most colorful) impact crater on Earth.

2) Dragonglass in Valyria. The people of Old Valyria called dragonglass “frozen fire” and mined it from somewhere nearby. They also refer to it as obsidian because of its shiny, black, glassy surface. Following meteor impacts, the molten ejecta rains back to Earth and cools into a black glassy rock (called Tektite) that shares many superficial similarities to obsidian. This might be some of the dragonglass described by the maesters.

3) Gold beneath the Fourteen Flames. The Kindly Man tells Arya that his early people slaved in the gold mines beneath the Fourteen Flames. Gold is not indicative of a meteor strike, but in a neat coincidence, a huge gold deposit was uncovered when a meteor (many times bigger than the one that killed the dinosaurs) hit South Africa nearly 2 billion years ago.

A meteor impact could not have been contemporaneous with the Doom — none of the Valyrian structures could have survived. It must have happened before any written records were kept on the planet, perhaps even millions of years ago. But it’s possible that the maesters knew of the meteor impact based on their own geological observations, and they told stories of it fracturing the Valyrian peninsula. Following the Doom, when it’s made clear all magic, knowledge, and recorded history were lost, it’s possible that the stories of the volcanic eruptions and the meteor impact that shattered the peninsula merged together in the retelling.

I present this history to you, the maesters of Essos and Westeros. The Doom may have once destroyed the greatest city our world has ever seen, but it should not preclude us from building again. Though this time, we might seek a slightly less geologically active area upon which to create our new Freehold.

your humble geologist
-Miles Traer, PhD

6 thoughts on “What caused the Doom of Valyria: A geological analysis

  1. Overall, a nice analysis. I particularly like the comparison with Krakatoa. But I would be rather conservative about the meteorite impact. Turning a Peninsula into an island may not necessarily be such a huge-scale catastrophic event (I would not compare it to the eruption of Toba, either, as these would have long-lasting global impact, which would probably still be observable 400 years later).
    I would keep to the idea of Krakatoa-like eruption with the earlier mentioned domino-effect.
    The Smoking sea, supposedly, was a low lying area (altitude only a few metres above sea level). The series of eruptions would have led to subsidence of the areas that had previously been uplifted by the building-up magma chamber. The following tsunami, as well as the massive landslides triggered by the events could have breached whatever barrier there was between the low-lying area and the sea. So the formation of the Smoking sea may have been a peaceful, although rapid, marine transgression.

  2. This is really nice! A meteorite impact! Probably the dragonglass (or tektites as mentioned in this article) interacted with the impactor during their formation and hence they bear the extraterrestrial signature that could kill the army of white walkers

  3. This is fantastic. I love it. My only question is whether or not George R. R. Martin actually researched the geology of his stories? Or is this all lovely coincidence? 🙂

  4. Caught a link to this over at iO9; fascinating take.

    I was wondering what your thoughts would be on a natural fission explosion as the impetus for the chain reaction.

    (Valyrian king-wizard pulls an Egg and tries an arcane ritual over “powerful” site, accidentally causes it to reach critical mass.) The explosion would certainly create a crater and set off the other disasters, and would also account for much of the physical landmass destruction. Hills would “burn” with radiation for a few hundred years, dragons would be incinerated in the nuclear fire, the sea would fill the crater but much of the architecture not destroyed in the initial blast would survive.

    I’m a dork, not a geologist, though, so I have no conception of the math that would be involved. I’d be interedested in hearing your thoughts though.

  5. Very interesting. There is a podcast called “Lucifermeanslightbringer”, and he theorizes that the planet of ASOIAF used to have two moons and that one was hit by a mereorite which destroyed it. He concludes that the shatered moon then fell on the planet, thus creating the first long night. I thought it was interesting that both of you have seemed to come to a simular conclusion.

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