The Earth split Westeros from Essos – 25 Mya

Westeros 25 million years ago. Click to enlarge.

Twenty-five million years ago (Mya), a line of fire and molten rock cut through the planet’s crust – like Wildfire cut through the ships at Blackwater Bay – and separated the previously joined continents of Westeros and Essos.  This spreading ridge is analogous to the mid-Atlantic ridge that was largely responsible for the breakup of Earth’s last super-continent of Pangaea.  The most striking evidence of this breakup is the morphological similarities of the shores of Westeros and Essos, appearing as though they could fit together as pieces of some geological jigsaw puzzle (similar to Alfred Wegener’s, and others’, observation that South America and Africa seemed to fit in the same way).  Based on the average spreading rate of the mid-Atlantic ridge (~2.5 cm/yr), we calculate that the rifting between Westeros and Essos began around 25 Mya.

Dammit mid-Atlantic ridge. Why are you always driving a wedge between us? (via Wikipedia Commons)

Furthermore, we propose that the Mountains of the Moon and the Hills of Norvos all belong to the same range, preferentially eroded in the east for reasons unknown (more on this later).  Also intriguing is the fact that the Hills of Norvos do not follow the same southwest-to-northeast trajectory as the Mountains of the Moon.  We cannot say for certain the orientation of the fault that created these ranges, but if they once befell a more linear path, then we can surmise that the Hills of Norvos have rotated in a clockwise direction, indicating that the rift between Westeros and Essos began in the north, and effectively “unzipped” to the south.  As of this writing, we cannot say with any certainty what caused the rifting (note: such radical changes in plate motion and the type of faulting can be found in Earth history, but generally require 100s of millions of years to come about, nearly 10 times longer than the process appears to have taken on this planet).

Perhaps the most controversial of our assertions is that plate tectonics are actively transforming the surface of Westeros, indeed the entire planet, and have done so for eons.  Yet the very presence of mountain ranges, a breathable atmosphere, and even life itself suggest that active tectonics must be considered in all analyses of Westeros.  Plate tectonics is the fundamental principal by which we understand Earth’s geology.  Among many others, tectonics explains how continents move, how rocks help regulate the atmosphere, and how earthquakes shake the ground and volcanoes ignite the skies.  Given active tectonics, we are somewhat troubled by the lack of earthquakes and volcanoes throughout the Seven Kingdoms.  While we cannot be certain, it is possible that the faulting responsible for creating the mountain ranges has since stopped, or at least slowed to a point when the recurrence intervals of large earthquakes and/or volcanic eruptions is long enough to circumvent the written records.  Though, at the moment, this remains speculation.

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When Dorne boiled – 30-40 Mya

Not surprisingly, the food served on the Bonneville Salt Flats has way too much pepper in it. (via Wikipedia Commons)

The salt of the Salt Shore, almost certainly an evaporite deposit, suggests that the region south of the Red Mountains, known as Dorne, was once submerged beneath a shallow sea.  Some time in the past, sea level was lower as glaciers trapped water as ice.  As sea level fell, a large depression, like the mouth of a leviathan, isolated itself from the adjacent ocean.  The result was an entrapped body of briny water exposed to the solar radiation (or perhaps to the heat of dragon’s breath, as we are unsure of the evolutionary history of dragons).  Over time, the sea began to evaporate away, leaving the salt behind (similar to the Bonneville Salt Flats near Salt Lake City, Utah).  The age of these deposits is somewhat difficult to constrain.  Evaporite deposits tend to form in hot, arid environments.  As previously mentioned, desert environments tend to form near 30°.  As will be discussed in the forthcoming sections, Westeros has gradually moved north throughout its evolution.  Given this tectonic drift, we speculate that the Salt Shore deposits are approximately 30-40 million years old.

Biologists have long known that dragons serve as a useful alternative to solar radiation [citation needed] (by Linda BlackWin24 Jansson, via Wikimedia Commons)

Additional geologic evidence supports this apparently brash claim of entire sea boiled away by the sun (or, again, dragons).  If town names are to be trusted as geologically accurate (a dubious, but necessary assumption), then we can infer the presence of green sandstone at the island of Greenstone.  Greenstone is a generic and generally unhelpful term, as it can apply to sedimentary or metamorphic rocks.  Combing through references to greenstone on Earth yielded a hit in the United Kingdom, where greenstone refers to sandstone contaminated with emerald-hued micas that was deposited within a shallow sea.  The geographic proximity of two separate rock types, greenstone and salt, consistent with shallow sea deposition strengthens the notion of a long lost sea.  The final piece of evidence comes from the town of Sandstone (guess which rocks we assume are there).  While sandstone can form in a variety of environments, we interpret these sandstones as deltaic, forming as rivers flowing from the Red Mountains reached the shallow sea and deposited their sediment load.

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Land of ice – 40 Mya

Westeros 40 million years ago. Click to enlarge.

It was a land of ice indeed.  Forty million years ago, a giant ice sheet, likely over a mile thick, covered nearly two-thirds of Westeros, and extended as far south as 40° north latitude, just shy of King’s Landing.  This ocean of ice would have dwarfed the great Wall (similar to the ice sheet that covered much of North America during the last ice ages).  To understand this land of ice, it is important to recognize the distinction between “greenhouse v. icehouse” planetary conditions and “glacial v. interglacial” conditions.  The former describes conditions that vary on time scales of millions of years or longer (like snowball Earth, nearly 650 Mya), while the latter generally describes climate variability on time scales of millions of years or less (like the last ice age, during the Pleistocene).  While the data is sparse, we propose that 40 Mya, this planet experienced icehouse conditions that created the massive ice sheet.  While it is currently unknown, the reanimation of hominoid biota currently north of the Wall may be a local indicator that appears concurrently with glacial cycles.  This area of bio-geological research deserves further investigation.

Pictured: Hominoid biota. Terrifying, reanimated hominoid biota. (courtesy HBO)

The physical evidence of this large-scale glaciation appears in a number of locations, most notably the sizable gap in the Mountains of the Moon, southeast of The Twins.  Only large-scale glaciation could provide the erosive power necessary to carve this region relatively flat.  In the north, west-northwest of Winterfell, the northern mountains are more subtly eroded, allowing for pines to grow below the tree line.  While not specifically mentioned in texts or personal accounts, large depressions left by the retreating glaciers are typically found on Earth.  And so we have interpreted two such basins: one extending southeast from Winterfell, and the other extending southeast from the Twins.  Each of these depressions, on the order of 100-1000 mi2, would later be filled with younger sediments deposited by rivers flowing from the nearby mountains.  While it is difficult to say with certainty, it is possible that the retreating glacier carved out the God’s Eye Lake, south of Harrenhal (similar to the Great Lakes of North America).  This geologic evidence strongly suggests that forty million years ago, winter appears to have come for the entire planet.

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The rise of the Black (Mountains) – 60-80 Mya

Westeros 60 million years ago. Click to enlarge.

Determining the age of the various Westeros mountain ranges is problematic without geochemistry; the wildlings make sample collection difficult.  However, we can infer ages based on the current shape, or morphology, of the mountains.  As Jon Snow and the men of the Night’s Watch have observed, the northern mountains, which we will call the Black Mountains, are jagged, rocky, snowcapped and quite treacherous to cross.  This jagged morphology suggests that the Black Mountains are relatively young, and the morphological similarity to the Rocky Mountains in the western US suggests that the Black Mountains are 60-80 million years old.  During this time of mountain building – called orogeny – an oceanic plate began to subduct beneath the northern territories of Westeros.  As the plate slid deeper into the planet, the heat of the mantle boiled away the water, which in turn melted the rock above, which then erupted forth as lava at the surface and created the volcanic mountain range (this form of volcanism is common on Earth, and is primarily responsible for the “ring of fire” around the margins of the Pacific plate).  Again, we are somewhat troubled by the lack of documented volcanism in the Black Mountains.  Our only explanation is that subduction of the plate ceased for some unknown reason, thereby killing the volcanic engine.

How subduction works on Earth. We assume it works the same on Westeros, because, physics. (via Wikipedia Commons)

The evidence of plate subduction is heavily inferred from geologic features found in Winterfell, specifically the hot springs that keep the town warm during winter, and the protective granite walls that secure the town’s interior.  While hot springs have multiple geologic origins, we propose that the Winterfell hot springs are the result of faulting – cracks in the crust that allow water to flow deep within the earth, get heated, then return to the surface via other faults (hot springs of this sort can be found all over the world, including coastal California).  The tremendous pressures involved as the plate subducted beneath the northern territories were surely enough to have caused faulting of this type, and the inferred volcanism would provide more than ample heat.  Thus, we interpret the Winterfell hot springs as fault-caused, consistent with plate subduction.  The protective granite walls offer more evidence of plate subduction.  Granite is an intrusive igneous rock, meaning that a magma chamber never erupted and the large body of molten rock cooled to granite within the earth.  Intrusive granites are common in subduction zones (think, Sierra Nevada mountains in California).  Given Winterfell’s proximity to the Black Mountains, we propose that a granite quarry must be nearby, easing the distance traversed by the giants of legend who hauled the granite slabs to Winterfell.

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