and the more geologically inclined can confirm or dismiss these ideas.

If it was a volcano under or surrounded by a shallow sea, these things don't always just explode without warning. They'll simmer and give off lava flow or percolate below the surface, super-heating the water and or building some impressive stores of lava/molten rock.

Let's say after building up pressure for a good long while, she did "blow" in an impressive display. That would account for the fact that these deposits do not seem to be exclusive to RoF, but you see evidence to the south where NRN is, etc etc.

If there was surrounding water, maybe the first attempts for the escaping steam and lava just kind of "burped" over the side in a circular fashion, creating our Ring of Fire?

Just some thoughts, wouldn't it be neat if we figured it out before the experts do?

GLTAL