[JP]

Originally Posted by mntlblok

Been pondering the same. But, my assumption was that the ground level was somehow rising rather than sinking. Does dirt grow? Can thatch become dirt over such short periods? Tectonics would drag the sprinkler system along with it, no? Can grass roots raise the dirt level? (They'd wait a million years. . .).

I don't think the ground level is rising significantly. Most of the planet surface is gradually sinking underground that will over time be melted in the earths core and will eventually return as new surface. Probably easiest to see in an area such as the land at the end of the Mississippi River--like a giant conveyer belt going down to the earths core.