Another common theme throughout the book is the concept of soil creation, from parent material.  I'm only familiar with our glacial till soil.  We have a bit of top soil, on top of clay that goes down many tens of feet in most places, I've found sandstone, but never bedrock around here.  So I assume the processes he refers to are applicable in shallow soils right on top of bedrock?  Is it safe to say that the only way I am going to gain any more topsoil is to wait for the next glaciation to bring it down(I'm very patient...)   How common are soils this deep in the world, I've always assumed this was normal, and shallow top soil only is rare, found in mountains etc, do I have that backwards?