CompuServe Messages

Hi, Kamron– >> What forces could be exerted on the ocean basins that could cause them to bend…. and then be pushed down into the material they are floating on … There are forces enough to move the continents – whether it is pull or push, those same forces require _something_ to happen when plates meet. They might just crumple up as with the Himalayas for a time, but something has to give. >> slab-pull? solids don't compress into significantly denser materials. I have referred you to the Scientific American article that mentions such transitions have actually been observed in olivine. How can you deny actual observed occurrences that explain what we see in the world so well? Why do deep quakes follow postulated plate boundaries so well if there is no such compression and no forces to drive/pull the plates down? The crust does indeed melt during subduction to some extent, hence the volcanoes of the Pacific Ring of Fire. But mostly it does not – those deep quakes are telling us so. The pressures are too great to allow such easy melting at great depths. Try 5-10 kilometers for the thickness of the oceanic crust. I do not have my references handy, being on the road again, but I am quite confident it is nothing like hundreds of miles. The cracking you speak of may indeed occur near the subduction zones, though I expect something to fill in the cracks generally and make them harder to spot. I will be interested to hear if anyone knows of such cracks (or how they might be avoided). –Doug