[WIP] World of Aduhr

[Pixie]

Now, I am jealous of your tectonics... Excellent work! The succession of failed rifts and multiple fractures makes it so "realistic". You say it explains "fairly well", but you might as well say it expains "comprehensively".

As for your questions,

- the oldest parts of the Pacific...
If you look at a map of the Pacific, it's very easy to spot a track of volcanic islands west of Hawaii, the further the older, and the oldest are aligned S-N, which means the Pacific was spreading in that direction in the past. Also, I know there was a rift close to Alaska at some time, now covered, this probably explains why the top northern part of the Pacific is younger than immediately to its south...

- clipping pieces of raster images to move with the plates
I don't know if it is possible, but you can draw lines and points in a plate, tag them as any object other than a tectonic plate and explicit to which plate they belong. They will move alongside the plate on the simulations.