I am talking to some students about how soil changes, and I've heard from soil samplers that the texture of the soil, i.e. whether it is sand, silt or clay, doesn't change in a human lifetime. It would be great to tell my students how long it does take, but I can't find this information anywhere. Is it something that isn't known? It must be a hard thing to determine?
The closest I've come to a statistic is that it takes thousands of years for soil to form, or that only a millimetre of soil forms each year, which is vaguer than I want to be.
Can soil chronosequences tell us the rate of weathering?