So much about geology is speculation about what might have happened in the misty, distant past. That's why the story about the glacier melting in Alaska at this very moment is so fascinating.
What happens when a glacier melts? Where does the water go? Obviously, it goes into the ocean, but then what? Does the ocean get deeper?
That's hard to measure, but in Alaska, the one thing that is easy to measure is that the land--not sea level--is what's rising.
(link to NY Times http://www.nytimes.com/2009/05/18/science/earth/18juneau.html?hp)
What used to be a salmon stream is now a grassy path. What used to be a golf course with a driving range that flooded at high tide is now getting new links. This is all happening now and over the past fifty years.
Fifty years is plenty of time for people to react to their new geographic reality. But what about Yonaguni? When it went the other way--when it submerged--did it happen slowly enough for people to react? Or was it a sudden, disastrous geologic event.
No one knows. Yet.