I don't understand your logic on this, Ostanes.
If anything disappeared in the depths of the sea, I would consider it to have "sunk." That seems to be compatible with the definition of sinking.
Disappeared and sunk are two different words and have two different meanings.
If Plato had wanted to say sunk instead of disappeared surely he could have.
However, he did not do so.
I can't believe I have to explain this. You may have a very valid point, but I don't see it. Your explanation is either missing some thought process which is completely obvious to you (but erroneously undisclosed), or else you are missing what seems perfectly obvious to me. I'll play nice and let you know my thoughts so they are no longer hidden. I hope you'll do the same.
Yes, Ostanes. "disappeared" and "sunk" mean two different things, but they also have meanings that can overlap. Anything which sinks does not necessarily disappear, but it might disappear if the substance into which the object sinks is opaque enough. A deep sea is effectively opaque because of that depth, so if you toss a bright, shiny coin overboard in the middle of the Atlantic, that coin effectively will have disappeared. The same thing with an island that subsides (read: sinks). Such an incredible, sinking island will have disappeared if the depth is greater than several hundred meters.
Now, let's be clear. The words you're quoting include more than merely "disappeared." What does "disappeared in the depths of the sea" mean? Let's take it apart, piece-by-piece.
"Disappeared" can mean several things. If something grows invisible (becomes completely transparent), like Harry Potter and the "cloak of invisibility," then it will have disappeared. It can also mean that something has moved out of the line of sight, or moved behind something else. In the case of something sinking into the ocean, the object will be "behind" or "underneath" many hundreds of meters of water and suspended particulates. Disappeared can also mean that something has achieved temporal discontinuity — ceased to have persistence in the time stream of physical reality. Can you think of any others?
"Depths" means a location which is down. That's funny. "Sinking" is also about the "down" direction — going to a location which is down, as in moving "down" into a liquid, or moving "down" into a solid when that solid becomes temporarily "liquid" (as in earthquake liquefaction) or has a temporary gap or chasm.
"Sea" means a large body of water, typically saline, as with the ocean, the Mediterranean, or Black Sea.
Okay, let's put these together: "disappearing" into the "depths" of the "sea" means to me, going down (sinking) into a liquid (water) to a point where the great depths effectively block one's ability to see that which has "disappeared."
Now, Ostanes, please tell me how something can
disappear in the depths of the sea without sinking.
Atlantis, if it existed, was not a continent, but uplifted oceanic plate (likely from convergent compression -- two tectonic plates colliding).
Tectonic plates are imaginary and do not exist in physical reality, and, if they did exist, it would be impossible for them to collide since there is no mechanism for them to do so.
In actual fact the mantle is cold and it's rigidity increases with depth, because otherwise seismic wave velocity wouldn't increase with depth.
Very interesting point. Certainly the consensus amongst scientists is that tectonic plates exist. They measure their movements with GPS. There are movements along fault lines and along the putative plate boundaries which tend to imply semi-rigid body movement against those distinct boundaries. From this we get earthquakes (also a movement). We have the compression of Earth's crust forming mountains. I can't imagine how such mountains would suddenly spring up (defying gravity) without some movement of the Earth to force them upward. And we have so many volcanoes which spew
hot (not "cold") magma.
Yet, scientists could be wrong. Your point about seismic wave velocity is interesting, and I'll look into it. Why do you say seismic wave velocity would increase? Would it increase with depth if it gets hotter with depth? Does sound travel faster in a hot solid than in a cold one? Is that what you're saying?
Somehow that seems counterintuitive to me. And some things in nature are counterintuitive. But it seems to me, with my limited understanding, that heat causes things to expand and I've always understood that sound (vibrational waves) travel faster in denser objects. Heat, because of expansion, makes objects less dense. Perhaps velocity is not directly related to density? What are your thoughts on these points?
