https://www.erasmatazz.com/library/life-in-general/marbles.h...

"""Civilization will not survive more than a few centuries into the future. If that sad assertion be true, then what will the earth look like in the far future? There was a television show some years ago entitled “Life After People”. It did a good job of showing how the artifacts of civilization would decay, erode, disintegrate, and disappear. What’s surprising is that most of the stuff won’t last more than a few centuries. Our big cities, freeways, bridges, skyscrapers, and so forth will be untraceable within a millenium of the collapse of civilization. What will survive for longer?

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This is why I occasionally dig a deep hole — perhaps two feet deep — on my land, drop a marble into it, and cover it up again. I always dig such holes on flat land halfway between the slope and the creek. The soil erosion here is slowest. For many years, the rains will slowly move dirt down the slopes toward the creek. On this flat section of land, the process will be very slow, and the loss of dirt to the creek will be matched by the gain of dirt from above. But eventually the former process will outperform the latter process, and dirt will start eroding away from above the marble. Eventually, all the dirt over the marble will be washed away and it will be exposed. """