Some Learning, page-8

ghawk,

I think your physics interpretation is basically correct but it comes down to the crustal rocks being able to contain the pressure. If the "crack" opens as a result of the pressure the speed slows. I've found a scientific paper published in 2001 which has analysed the tectonic controls of kimberlites in South Africa. The conclusion is that shear zones and crustal faults are too weak to form kimberlites in and that kimberlites in South Africa are found parallel to these structural corridors but not on them.

Eshmun

http://www.colby.edu/academics_cs/courses/GE127/upload/Vearncombe2002.pdf

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