Your question - through no fault of your own - involves a tangle of cultural elements. Many of the references you cite originate in literature even though they seem to refer to folk belief (even when folk tradition is not really involved). The folklorists Foster and Tolbert (2016) have recently coined the term "folkloresque" to describe this sort of thing. Literature that seems like it is drawing from old myths and legends can be enormously seductive, even to the point of inspiring a folk tradition, for the barrier separating folklore and literature has always been porous.

The ancient world or even pre-industrial Europeans did not have folk traditions about Atlantis, for example; this was a construct of Plato's (possibly based on his uncle's report of information about something else, which he gathered in Egypt), but the idea was so powerful that it has seeped into modern folklore.

Egyptologists have found a few examples of ancient Egyptian tombs with devices that were intended to drop a large stone to seal an entrance once priests were finished establishing the final resting place, all as a means to cut off access to thieves. This idea was amplified in modern film and literature to the point where, again, it has entered modern folk belief that these devices were widespread internationally, often transforming into traps that are set, rather than devices that have already been "sprung."

On top of all of this is the modern folk belief that "all legends are based on something real." Some legends may have a real antecedent. Other legends may have wind placed in their sails by real events that didn't create the legends, but which the folk use to justify believing in a legend. That said, many legends originate in ways that are not entirely understood, but they are not necessarily based on anything real. Because of this modern folk belief, a cottage industry has sprung up to find the source of every myth and legend ever documented, and those narratives often, again, seep back into modern folk belief (especially the idea of lost continents and lost civilizations). This process creates a great deal of the motifs you are describing, whether they remain in literature and film or play into modern folklore (and return to literature and film, a self-reinforcing feedback).

As if the jumble of issues couldn't get more complex, there are a variety of myths and legends that refer to some distant treasure that has been lost, is elusive, or requires some great search to find. This motif has, indeed, been pervasive in folklore. That doesn't mean these treasures are real - nor does it mean that there are no treasures out there! The legends exist on their own, and at the same time, wealth gets deposited in the oddest of places and sometimes it is lost - putting wind in the sail of a variety of legends about this sort of thing. I have written a short piece on this (and am working on a book that will develop this further): "Lost Mines and the Secret of Getting Rich Quick".

Because of the nature of the folkloresque, folk belief, literary musings, etc., the motifs you are describing are going to be wrapped in a swirl of cultural elements - and sometimes real things - all of which can be difficult to sort out. You have asked a generic question about the entire spectrum of these literary and folk traditions, so I have given you a generic answer. Any one of these can (and many have) been asked of /r/AskHistorians, but the questions persist because the modern folk traditions surrounding many of these are vibrant and by their nature remain insatiable.