Putting green rootzone depth after 27 years

It's useful to know the depth of the rootzone, whether that's for water management, organic matter management, curiosity, considering whether to rebuild, or considering how to regrass. This photo shows a 27 year old bermudagrass green that was constructed with 30 cm (12 inches) of sand above the gravel layer. An additional 16 cm (6 inches) of material has accumulated above the original rootzone.

That works out to 6 mm per year; about 0.25 inches per year. I don't know…