I don’t know if anyone else has ever encountered those TV shows on ‘if humans suddenly vanished’; they always assume that everything made by man would vanish very quickly, cities engulfed in a few decades by lurid CGI jungles. Anyone who has studied any archaeology knows that couldn’t be farther from the truth. If neolithic fish traps can still be seen on Google Earth (if you know what to look for), it is rather unlikely that a modern city would vanish in a century. Chernobyl has given us a fascinating case study on just how a modern city that is totally abandoned by man does or does not decay.
Hard structures take millenia, some will probably take a timescale closer to geological time to vanish. Yet even minor disturbances leave their traces. Old abandoned roads in New England are legion, New Hartford alone has four major ones and an entire settlement. These are easy to find, the stone walls, the parallel form of the depression, often enhanced by becoming a water course, the different types of vegetation willing to grow on compacted soil, old cellar holes, unusually massive trees or tree stumps, and so forth. But even single use logging roads can be found decades later: unusually straight, wide paths in the forest, distinctive scars on trees.
Sometimes, inadvertently, a single event remains recorded. Up on Yellow Mountain the other day with a state forester, we came across a beech tree that had a distinctive ’14’ cut into it. Judging by the age of the beech tree and the style of the mark, that ’14’ was made by a CCC crew back in the 1930’s when they came through clearing gypsy moth infestations and removing gooseberry bushes (an attempt to stop the life cycle of a blister rust that damages white pine). The ’14’ would have been a mark by the crew, presumably no. 14, that they had finished that quadrant to which they were assigned. Nearly eighty years ago some one, probably a young man who is now elderly if not dead, made a quick mark on the tree. Eventually, that beech will fall; but for the time you can almost see the crew working what increasingly feels like a truly different century (it is, technically, I know!), and yet that tree is a physical connection across decades.