the soonest possible time being 30,000 years ago. Is this long enough for all traces of their civiliation to disappear?
No.
Note that Dumbledore says something like “erased Atlantis from time”, which suggests more than just the passage of 30 k years is involved in hiding the traces.
Note that Dumbledore says something like “erased Atlantis from time”, which suggests more than just the passage of 30 k years is involved in hiding the traces.