Quote Originally Posted by Charerg View Post
@Durakken: The Agalhaic plates closely mirror the Pacific and Nazca plates on Earth. In other words, they're part of a single oceanic plate that has split in two because it is subducted on both sides by continental plates. Speaking of subduction, my understanding is that subduction is actually the main force driving plate movement (and ridges and rifts occur as a result, rather than being the driving force). If you look at Earth, the East Pacific Rise is expanding about 15.1 cm/y at its most expansive point. By comparison, the Atlantic ridge (where bordering plates are subducting rather than being subducted) expands a measly 3.5 cm/y at its most expansive point.
As I understand it, this has not been settled, whether it is one way or the other. I can give a guess at explaing the faster movement, but I'm not informed enough there.
The mirroring of the Pacific/Nazca plate; That was my guess. The problem I have with it is that it is too large and doesn't look like it would develop from the shapes. To me, the Nazca plate looks like it was created due to the various stresses created by the other plates, specifically the continental plates where as the Agalhaic plate of your world looks like it isn't informed by anything other than just wanting another plate there that doesn't really do anything.