<< I don't get it. Yes, the plates move in different directions,
that's obvious. If every pair of nearby plates were converging
(or diverging), the planet would have to be shrinking (or growing).
I can't visualize what Shaun is suggesting here - that two plates
may approach each other without colliding? Or that some collisions
have a lateral component (that can't be surprising)?
Actually the planet has been growing, when the planet was one land mass, it
was 80% the size of what it is today. They can tell by the way the