From the texts, we know that the kingdoms have persisted for thousands of years, with many kings rising and falling as the tides (though we won’t concern ourselves with kings or kingdoms here).  From the same texts and carefully surveyed maps, we also know that Westeros contains mountain ranges, hot springs, granite, gold mines, deserts, ice walls, and red, grey, and black stones used to construct castles.  To the carefully trained eye – admittedly trained here on Earth – each of these elements betrays a rich and complex geologic history of the continent, reaching back over 500 million years.

We began with a simple question: what is the size of the Game of Thrones planet?  After all, understanding processes at the planetary scale is crucial to geology.  Past researchers have attempted these calculations without consideration of the coupled system of climate and geology, and these are essential initial attempts.  We started with the most basic of observations: it is cold enough in the north to maintain the Wall of ice that shields the continent from the White Walkers, and it is warm enough in the south that the maps are colored as deserts, an environment encountered most recently by the Khaleesi, Daenerys Targaryen, at approximately the same latitude on Essos.

On Earth, deserts appear within a general latitude range, with most near 30° north (for example, the Sahara in Africa) and south (for example, the Atacama desert in South America).  This is due to circulation of atmospheric Hadley cells.  The harsh cold of the north, and the presence of the Wall for millennia, suggests that the Wall is at or near the Arctic Circle, currently at 66.5° north latitude on Earth.  So we have some approximate bounds for Westeros, stretching from 30° to 66.5° latitude, and all of it likely on the northern hemisphere.  Finally, we have it on good authority that it is 3,000 miles from the Wall to the southern flank of the continent, the deserts of Dorne.  Using simple geometry, we calculate that the radius of this dragon-inhabited planet is 4,297 miles, slightly larger than Earth’s radius of 3,959 miles, but still remarkably similar.  Fortunately for us, this won’t be the last time we assume similarities between this planet and our home on Earth.