In these days of climate change, the notion of coastal areas going underwater is a familiar fear. But it's not a new one; we have stories of drowned lands going back for thousands of years.

The famous example, of course, is Atlantis. Which Plato wrote about for allegorical purposes, not literal ones: he was making a point about society, building up Atlantis as a negative foil to the perfections of Athens. That hasn't stopped later writers from taking the idea and running with it, though, with interest particularly surging after Europeans learned of the New World. That's one of many locations since identified with Atlantis, with considerable effort expended on identifying a real-world inspiration for Plato's story (Thera leads the pack) . . . alongside wild theories that build up the sunken land as a place of advanced technology and magic. The supposed "lost continents" of Lemuria and Mu -- which may be the same thing, or may be synonymous with Atlantis -- are later inventions, discredited by the development of geological science.

We don't have to lose whole continents to the ocean, though. The shorelines of northern Europe are dotted with legends of regions sunk below the waves: the city of Ys on the coast of Brittany, Lyonesse in Cornwall, Cantre'r Gwaelod in Wales' Cardigan Bay. Natural features can contribute to these legends; the beaches of Cardigan Bay have ridges, termed sarnau, which run out into the ocean and have been taken for causeways, and environmental conditions at Ynyslas have preserved the stumps of submerged trees, which emerge at times of low tide. The so-called Yonaguni Monument in Japan and Bimini Road in the Bahamas are eerily regular-looking stone formations that theorists have mistaken for human construction, again raising the specter of a forgotten society drowned by the sea.

Many of the examples I'm most familiar with come from Europe, but this isn't solely a European phenomenon. I suspect you can get stories of this kind anywhere there's a coastline, especially if the offshore terrain is shallow enough for land to have genuinely been submerged by rising sea levels. Tamil and Sanskrit literature going back two thousand years has stories about places lost to the ocean, which is part of why some modern Tamil writers seized on the idea of Lemuria (supposedly positioned to the south of India). It doesn't even have to be salt water! A late eighteenth-century Russian text has the city of Kitezh sinking into Lake Svetloyar: a rather pyrrhic miracle delivered by God when the inhabitants prayed to be saved from a Mongol invasion.

Some drowned lands are entirely factual. Doggerland is the name given to the region of the North Sea that used to connect the British Isles to mainland Europe, before rising sea levels at the end of the last glaciation inundated the area. Archaeological investigation of the terrain is difficult, but artifacts and human bones have been dredged up from the depths. If we go into another Ice Age, Doggerland could re-emerge from the sea -- and if it had been flooded in a later era, what's down there could include monumental temples and other such dramatic features. We're robbed of such exciting discoveries by the fact that it was inhabited only by nomadic hunter-gatherers . . . which, of course, need not limit a fictional example!

Doggerland was submerged over the course of thousands of years, but most stories of this kind involve a sudden inundation. That may not be unrealistic: after an extended period in which the Mediterranean basin was mostly or entirely cut off from the Atlantic Ocean, the Zanclean flood broke through what is now the Strait of Gibraltar and refilled the basin over the course of anything from two years to as little as a few months. Water levels may have risen as fast as ten meters a day! Of course, the region before then would have been hellishly hot and arid rather than the pleasant home of a happy civilization, but it's still dramatic to imagine.

Then there are the phantom islands. I have these on the brain right now because the upcoming duology I'm writing with Alyc Helms as M.A. Carrick, the Sea Beyond, makes extensive use of these, but they've fascinated me for far longer than we've been working on the series.

"Phantom island" is the general term used for islands that turn out not to be real. Some of these, like Atlantis, are entirely mythical, existing only in stories whose tellers may not ever have meant them to be more than metaphor. Others, however, are a consequence of the intense difficulties of maritime travel. Mirages and fog banks can make sailors believe they've spotted land where there is none . . . or they see an actual, factual place, but they don't realize where they are.

To understand how that can happen, you have to think about navigation in the past. We've had methods of calculating latitude for a long time, but they were often imprecise, and a error of even one degree can mean your position is off by nearly seventy miles/a hundred kilometers. Meanwhile, as I've mentioned before, longitude was a profoundly intractable problem until about two hundred and fifty years ago, with seafarers unable to make more than educated guesses as to their east-west position -- guesses that could be off by hundreds and hundreds of miles.

The result is that even if you saw a real piece of land, did you know where it was? You would chart it to the best of your ability, but somebody else later sailing through (what they thought was) the same patch of sea might spot nothing at all. Or they'd find land they thought looked like what you'd described, except it was in another location. Well-identified masses could be mistaken for new ones if ships wrongly calculated their current position, especially since accurate coastal charts were also difficult to make when your movements were at the mercy of wind and current.

Phantom islands therefore moved all over the map, vanishing and reappearing, or having their names reattached to new places as we became sure of those latter. Some of them persisted into the twentieth century, when we finally amassed enough technology (like satellites) to know for certain what is and is not out there in the ocean. There are still a few cases where people wonder if an island appeared and then sank again, though we know now that the conditions which can make that happen are fairly rare -- and usually involve volcanic eruptions.

The sea still feels like a place of mystery, though, where all kinds of wonders might lie just over the horizon. And depending on how much we succeed or fail at controlling global temperatures and the encroachments of the sea, we may genuinely wind up with sunken cities to form a new generation of cautionary tales . . .



(originally posted at Swan Tower: https://is.gd/kKc80k)