system
Given the following post, respond as if you're commenting on Reddit:
human
[ASOIF] What exactly happened at the doom of old Valyria?

I don't think that there is ever a definitive explanation in the books and I'm still reading through A World of Ice and Fire. If the exact answer isn't in the books, what are some prevailing theories that would still be possible within the world?
gpt
The prevailing theory is a massive seismic event which rent the earth for leagues, spewing unimaginable amounts of magma and ash into the sky and creating massive tidal walls in all directions. Even now it is mentioned that the sky is always red over Valyria, and that any winds that drift across the sea from the doomed continent smell of sulfur and ash to this day. The ancient Valerians were well versed in magic of blood and fire, which led some to believe that some terrible work of their own making brought the doom upon them. Perhaps the wrath of some angry god or a terrible beast sleeping deep within the Earth. Since the shores of Valyria are said to be cursed few and less have ever tried to investigate, and the claims of those who say they have and survived are unsubstantiated at best. Perhaps we may never know, or perhaps the Doom was merely a portent of the events to come. Once forces as powerful as whatever caused the Doom  are roused they rarely subside without great effort and sacrifice.