In modern times hippie folk singer Donovan might have contributed to the myth.
Hail Atlantis! 
Just for fun.
One of the best quotes I’ve ever read:
Basically, yes. The Decline of the West stuff is quite deliberate on the part of Lovecraft, and the Old Ones were into the process of decadence and degeneration long before the second, successful, shoggoth revolt. By that time they had lost most of their superior ancient art and technology, and it was climate change that ultimately led to the abandonment of their cities and colonies and forced them underground and underwater. Indeed, at that point mere shoggoths were able to rise up and do for them, whereas the original Old Ones were able to hold their own against the spawn of Cthulhu. But note that the thing glimpsed in the Cold Waste, the brief sight of which drove Danforth insane, wasn’t no shoggoth 
I was under the impression that Plato based the tale of Atlantis on the Thera Eruption and the subsequent collapse of the Minoan civilization on Crete.
Maybe, but that was 1200 years prior, as far as we know the greeks had no records going back that far (and neither did the Egyptians, really, except lists of Kings). But even if he had the glimmer from Thera it was possible, the whole idea of the tale is that Atlantis was Athens and Athenians better get their shit together or they will be destroyed… which oddly enough- they were, but not in any way Plato thought.
Plato was telling a moral tale about arrogance and avarice, having watched Socrates being forced to drink Hemlock. The Old Athens was great, and beat Atlantis, but Athens (as did Atlantis) was falling into a decline :
“*For many generations, as long as the divine nature lasted in them, they were obedient to the laws, and well-affectioned towards the god, whose seed they were; for they possessed true and in every way great spirits, uniting gentleness with wisdom in the various chances of life, and in their intercourse with one another. They despised everything but virtue, caring little for their present state of life, and thinking lightly of the possession of gold and other property, which seemed only a burden to them; neither were they intoxicated by luxury; nor did wealth deprive them of their self-control; but they were sober, and saw clearly that all these goods are increased by virtue and friendship with one another, whereas by too great regard and respect for them, they are lost and friendship with them.”
However, the Atlanteans became corrupt as:
“…when the divine portion began to fade away, and became diluted too often and too much with the mortal admixture, and the human nature got the upper hand, they then, being unable to bear their fortune, behaved unseemly, and to him who had an eye to see grew visibly debased, for they were losing the fairest of their precious gifts; but to those who had no eye to see the true happiness, they appeared glorious and blessed at the very time when they were full of avarice and unrighteous power.”*
It’s a metaphor. Athens was great when it beat Darius at Marathon, but it has slid into decline. Plato couldnt speak openly, as he didnt want to have to drink hemlock.
In Kritias and Timaios Platon tells that Atlantis is as big as Asia and Africa combined.
To avoid being misled, one need to know, that to the ancient Greeks, Asia was Minor Asia (now Turkey) and Africa was land strip present day Libya close to the Mediterranian Sea.
as I say in the webpage I link to WAY above, that was for a long time the supposed source of Atlantis myth. But it precedes the first appearance of Atlantis in Plato by a thousand years, and I have serious doubts about the story being kept alive that long.
Still, it’s showy, dramatic, and for a long time was presented in the popular press as THE explanation.
I suspect that it’s much more likely that an event closer in time was responsible for the inspiration. again, as in the above link, the destruction by flooding of the island of Atlantae provides a good candidate, only a relatively short time before Plato. The description of Atlantis, that land beyond the Pillars of Hercules, has been suggested to be a description of Northern Africa made by travelers who did, indeed, go “beyond the Pillars of Hercules” to get there. It matches pretty well. No sunken islands or continents required, and no millennium-old memories to be retained.
Mind you, I’m not saying that Plato (and Socrates) were reporting actual events. I do think that dr. Deth is correct about this being metaphor and allegory. But such fictions often have their inspiration in real events.
No doubt. Just enough realism to make the story some less fantastic.
Will Gene Autry have a role? 
( The Phantom Empire - Wikipedia , for those of you not steeped in the classics.)
I own a copy of that. Wonderfully awful stuff.
But I suspect that, when it came time for people to try to do “serious:” adaptations of “Lost World” stories, producers thought of the ridiculous capes and stilted dialogue and plywood tanks and thought they would just look like this. I’m kind of amazed that Merian C. Cooper’s She ever got made.