So, how about this:
Some 336 meters into the cave, the caver stumbled across something extraordinary—a vast chamber where several stalagmites had been deliberately broken. Most of the 400 pieces had been arranged into two rings—a large one between 4 and 7 metres across, and a smaller one just 2 metres wide. Others had been propped up against these donuts. Yet others had been stacked into four piles. Traces of fire were everywhere, and there was a mass of burnt bones. …
Picture at the link.
After drilling into the stalagmites and pulling out cylinders of rock, the team could see an obvious transition between two layers. On one side were old minerals that were part of the original stalagmites; on the other were newer layers that had been laid down after the fragments were broken off by the cave’s former users. By measuring uranium levels on either side of the divide, the team could accurately tell when each stalagmite had been snapped off for construction.
Their date? 176,500 years ago, give or take a few millennia.
Therefore, this was the work of Neanderthals, not modern humans.
Wow.
What remnants of modern life do you suppose will still be around in 175,000 years or so?
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That cave sounds incredibly cool.
What might be left of our lives in an equivalent span… maybe bits of integrated circuits.
Loads of mines would still be left even that far ahead — at least enough to see they were clearly artificial. Physical items… not a lot is going to make it that far. I recall a semi-humorous SF story I read years ago in which cities of our era were being mapped out based on ceramic toilets, almost the only identifiable artifacts in the digs.
Ceramic toilets and sinks, if they get buried intact enough to be reconstructed, might remain recognisable for a really long time.
Some traces of concrete roads might remain just as long or even longer, as well as some of the concrete foundation pillars much of the modern construction around here is built on. Those are square pillars of reinforced concrete up to 20-30 meters long, pounded into the soil until they rest on a firm layer of compacted sand (or maybe rock, elsewhere – the Netherlands has no reachable rock underfoot, but Germany, France etc. probably do even in areas that still have enough ‘soft’ earth on top to need these foundation pillars) that won’t move in the next few centuries at least, and can support the weight of the concrete and/or brick (or maybe stone, elsewhere) building. For the usual 2-3 level dwellings around here these foundation pillars are usually no more than about 10-15 meters long, in a grid that will support the concrete foundation walls. I expect, even after the houses have been demolished and the land sunk beneath the ocean for a few eons, something like subsurface sonar could still find traces of those concrete pillar grids, as we’re not near any active subduction zones or volcanoes, nor on the edge of a continental plate.
The Netherlands is mostly swamp and sand dunes, so we need foundations for our buildings. There’s an old song about Amsterdam being built on poles: its iconic canal houses’ centuries old foundations are supported on 30 meter tall wooden poles with many layers of strong leather on top, instead of the concrete we use today. Still those foundations from the 1600s and 1700s last, and do their jobs, as long as they stay submerged (below the top of the groundwater level). Concrete would last much longer.
Hanneke, you’re reminding me about our tour guide explaining how Venice was built on a foundation of massive tree trunks and wooden pilings, and those lasted extremely well as long as they were submerged in the oxygen poor water. Let me see … here:
Venice Island was built on a foundation of 10,000,000 underwater wooden logs or 8 to 10 tree logs per sq meter. Trunks function as roots. 1200 years later, those same trunks still support almost all of central Venice
I find it stunning that people would even think of building a city like that, and then actually do it, at least twice, since Amsterdam was built in kind of the same way.
I dunno about the term “construction” for this. “Ceremonial site”, certainly.