"Know, O prince, that between the years when the oceans drank Atlantis and the gleaming cities, and the years of the rise of the sons of Aryas, there was an Age undreamed of, when shining kingdoms lay spread across the world like blue mantles beneath the stars ... " -- The Nemedian Chronicles
I've blogged before about the brilliance of Robert E. Howard's idea to create the Hyborian Age. It's important to remember that Howard wrote several decades before the formulation of the theory of plate tectonics, and while continental drift had been suggested in vague terms by a few scientists, there was little acceptance of the idea because it lacked compelling evidence until it was combined with sea-floor spreading, radiation heat, and various other lines of evidence that crystalized in the late 1950s and early 1960s into the theory of plate tectonics.
Therefore, Howard's Golden Age, the Hyborian Age, was framed by disasters; global cataclysms on the scale of the Biblical flood, that plate tectonics now tells us were impossible.
However, of course, in a fantasy setting there's no reason why scientific rigor has to be maintained. The more I think about it, the more I think I was perhaps wrong, or at least barking up a slightly wrong tree, when I wrote my blog post "Realistic" maps. Rather than realistic by plate tectonics standards, I think realistic by earlier 20th century standards would be more fun. After all, the allure of lost continents, (Zealandia, Sundaland and Kerguelen notwithstanding) and massive natural disasters shaping the history of life on earth is ingrained in our cultural heritage, and too alluring a prospect to ignore.
Speaking of which, I had two options for some images of lost civilizations, both by Les Edwards. Since I couldn't decide which one I liked best, I attached them both.