text:  uh... they form current that come up and they drive the surface material apart and that's constantly placed up in the center and it it goes back down at the edges and that is analogous to what happens in uh... you know the kill away of fire pit they've got a lot of photographs of uh... the kind of mechanism that's been proposed for the plate we know when the material comes up it must go someplace otherwise the earth would be expanding constantly and then they