CompuServe Messages

Hi, Kamron– Regarding your answer to Mike in this thread, the mantle is not liquid, it is plastic. I think even the thin asthenosphere between lithosphere and mantle is only partially liquid if any. "Plastic" means it is a solid in a state where crystalline bonds can break and reattach in new places in patterns that let the material flow sort of like a liquid, but _much_ more slowly. It is like the difference between independently rolling balls (the liquid), and a centipede which remains bonded to the surface unlike the balls, yet still manages to move. This offers an answer to your remarks about how the convection currents can push/pull the crust – I suspect the subducted lithosphere and the convecting mantle are bonded together, even if the bonds are shifting from time to time. They are likely coupled much more strongly than a liquid can be coupled to a solid. It also offers the answer to your problem with material melted out of the subducted plate rising straight up instead of following the "weakness" where the subducted lithosphere meets the mantle – I suspect there is no such weakness as far as a faster-moving liquid is concerned, that the lithosphere is already bonded with the mantle into a continuous solid. It is critical to ask whether the magma starts rising in the realm of plasticity, because that is where I expect this bonding would form, more or less. –Doug