Tales from a Westeros Geologist

Westeros Geologic Map cropped

Day 1 – Planet… Hodor

Well, the gateway seems to have worked. I won’t bore you with the details, but we seemed able to rip open a hole in the cosmos and travel through the interdimensional portal to this strange place. The gateway engineers back on Earth seemed pretty confident that I would make it to Westeros, but until I saw the Weirwood trees, I wasn’t so sure. I guess I owe them a gin and tonic when I get back.

In case you’re wondering, I’m here to survey the geology of this planet. I tried to ask a few people around here if the planet had a name, but they looked pretty dead, so I guess I shouldn’t have expected an answer. I’ll go ahead and call it something that totally doesn’t mean anything like a phrase garbled and transported through time. I’ll call it Planet Hodor.

Based on the smoldering stones and the freezing temperatures, I’m guessing I’m near Winterfell. Doesn’t look like anybody’s around, so I should probably find a place out of sight in case the Starks, Boltons, or anyone else comes by.

Day 7 – Winterfell

I’m lucky that I started off here next to Winterfell. The hot springs have kept me warm all week as I surveyed the area. This is good for a number of reasons. 1) I’m not dead, and 2) They strongly suggest that Westeros is tectonically active, so I should have some great geology to analyze during my time here.

You see, hot springs can form when faults break through the crust of a planet. Heated fluids trapped in the rocks deep underground travel along these cracks to the surface. I used to visit hot springs in central California like this, but with all the naked flower children, the less said about that the better.

The Great Keep seems to be made of granite, so I’m guessing there’s an exposed outcrop nearby large enough for a quarry. Granite is an intrusive igneous rock, so it formed deep underground and cooled off over a long time. It’s commonly found under mountain ranges, so I’m guessing it probably came from the north somewhere. Granite is promising because it, too, suggests active plate tectonics on Planet Hodor. As one plate slid beneath another to create the northern mountains, the water and other volatiles already soaked into the plate boiled off, melted the surrounding rock, and created huge quantities of magma that later cooled to become the granite batholith.

A promising start indeed! Faults, granite, and I just found some caves under the castle! I’ll search those tomorrow. I’m sure nothing bad will happen.

Day 8 – Caves

Ok, so those caves are pretty creepy. The caverns seem to be much bigger than the castle, and they’re filled with statues carved of pale stone, like death masks of ancient kings. I had to travel deep into the narrow tunnels to really look at the rock walls. They were dark, much like the rest of the stones used to build the castle. I knocked off a small piece – hardly the worst thing that’s happened in Winterfell – and brought it back to the surface to analyze.

Westeros 300 Mya
Westeros 300 million years ago

Caves are common in limestone landscapes, and I’m guessing that this is limestone. It typically forms in shallow ocean environments near the tropics. The rock represents the basement of large reefs. On Earth, reefs only really show up between 30 degrees north latitude and 30 degrees south latitude. I don’t know exactly where Winterfell is, but with all the snow and wind and ice, I’m doubting I’m in the tropics.

Once again, we have evidence of plate tectonics. At some point in the geologic past, Winterfell must have sat much farther south. The continent gradually moved north until it reached its current location. Based on plate speeds on Earth, this means that the Winterfell limestone is probably around 300 million years old. In a total coincidence, this is roughly the same age as limestone deposits in Great Britain that were used to build medieval castles that inspired fantasy authors!

Anyway, yesterday I saw someone walking around with a black flag adorned with a man hanging upside down and no skin. So, I’m gonna leave for… anywhere else, really. Probably south.

Day 12 – The King’s Road

I’ve been on the road for four days and The King’s Road is surprisingly flat. I was hoping that the Westerosi engineers might have cut through some cliffs or something and provided me with beautiful rock faces to look at. But so far, nothing. It’s fine. I expect it won’t be much longer.

Day 19 – The King’s Road

Ok, wow. This road is long.

Day 31 – The King’s Road

Oh my GODS (both the Old and the New) the King’s Road is LOOOONG. Seriously, this thing is taking forever. At first, I thought I might care about road cuts and rock outcrops, but this is just too much. And that guy at the bridge wasn’t very fun to deal with either. Made me do… things… to cross.

Day 43 – Mountains of the Moon

I suppose I should be grateful that I’ve reached these colossal mountains. The locals call them the Mountains of the Moon. They look a lot like the Himalaya on Earth, with jagged, snowcapped peaks that stretch to the sky.

Westeros 80 Mya
Westeros 80 million years ago

The mountains must be relatively young; They haven’t eroded away to rolling hills. On Earth, when plates come together, one plate (usually the denser oceanic plate) slides beneath another plate (usually the less dense, and hence more buoyant continental plate). This is what led to the creation of the Andes in South America and nearly all of the volcanoes along the western side of the Pacific “Ring of Fire.” But that’s not how the Himalaya formed.

The Himalaya formed when India slammed into Asia. Both bodies were mostly made of buoyant continental crust, so neither plate really wanted to subduct beneath the other. So they just slammed together, and the incredible forces involved combined with the high buoyancy created the highest mountains on Earth. Something like this must have happened here, especially because the Mountains of the Moon appear to be so wide. This means that northern Westeros was, at some point, detached and separate from southern Westeros. I guess the Starks and Lannisters just couldn’t stand to be apart.

Day 56 – A Problem

Something has been bothering me about this area. I can see the Mountains of the Moon to the east and west, but the area here around the north branch of the river Trident is very flat. All due respect to this river and those who live here (including that creep, Frey), there is just no way it could have eroded out this entire valley. There must be something else going on.

And not to pile on, but how in the heck is this river even possible? On Earth, the vast majority of rivers start in highland areas and get bigger and bigger as they progress downhill. But the northern branch of The Trident seems to just… start. Maybe it’s a massive release of subterranean waters captured in the Winterfell limestone, but that seems a stretch at best.

Day 60 – A Land of Ice

I figured it out! No, not the river. That still makes no geological sense. But I think I’ve determined what created this low valley in the middle of such impressive mountains. It was an ice age!

Westeros 40 Mya
Westeros 40 million years ago

Glaciers are really the only thing powerful enough to erode out this much material. So at some point, there must have been a significant ice age with glaciers that extended down at least this far from the north. This would explain the low lying terrain here, and might even explain the presence of the large God’s Eye Lake. I managed to find an outcrop (bunch of rocks) through what looked like a large moraine (stuff piled up at the edge of a glacier), and sure enough, I found glacial till (sharp sediment deposited by ice). Success!

If we temporarily ignore that the climate on Planet Hodor makes no damn sense, there might be an interesting parallel that we can draw on Earth. When the Himalaya began to uplift, erosion ramped up and exposed fresh rock faces to chemical weathering. This weathering process typically absorbs a lot of carbon dioxide and might have helped push global temperatures lower. I’m not saying the Westerosi ice age makes total climatic sense, but it doesn’t seem too far off.

Day 61 – I’m Outta Here

From my current location, there are just too many opportunities to survey potentially excellent geology. I could about-face and try for The Wall, though Wildlings might make sample collection difficult. I could try to make it west to the Iron Islands and look through the banded iron formations that might mark the birth of a breathable atmosphere on Planet Hodor. I could trek to Casterly Rock and analyze all of that Lannister gold, assuming there’s still anything left. I’ve always been intrigued by the red-hued sandstone in King’s Landing. The scandalous wedding of Edmure Tully to Roslin Frey wasn’t the only thing to be stained red in Westerosi history! What… too soon? Each path is fraught with peril – like Walder Frey, or Ramsey Bolton, or The Mountain, or Sandor Clegane, or The Night’s King, or Melisandre, or The High Sparrow, or Maester Qyburn, or Littlefinger Baelish, or… really, I’m just afraid of Cersei.

Even with just a smattering of geological clues, I’ve already been able to infer so much about Westeros and its evolution. Geology, at its heart, is a deeply creative vocation. Imagining Earth’s past is, in many ways, like imagining a fantasy planet – a planet Hodor, if you will. We populate our imagination with scrupulous observations about Earth’s climate, ecology, and yes, rocks, to assemble fantastic histories that seem to border on mystical. But they’re true. And that’s why I do this. The pursuit of geology is the pursuit of the truly awesome forces that shape planets, transform climates, and drive human evolution. Most of the time, these forces are beautiful. And sometimes, they can be even more terrifying than a possibly undead Mountain.


If you enjoyed this project and want to keep exploring real science in fictional places, you can come hear me speak about more Westerosi geology.

This post is part of the Science of Game of Thrones blog carnival. You should check out all of the other amazing posts:

One reason scientists and science writers want to talk about Game of Thrones by Matt Shipman

Dire Wolves Were Real by Brian Switek

The Epidemiology of Greyscale by Tara C. Smith

A Storm of Chemistry by Raychelle Burks

The Heating Engineers of Winterfell by Jesse Emspak

Biology Would Leave the Game of Thrones Dragons Grounded by David Hone

Winter is coming: Climate change and biodiversity beyond the Wall by Jacquelyn Gill

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