If zombies finally take out humanity, or some plague wipes us out, most of our structures will crumble, collapse and be reclaimed by nature. The Hoover Dam on the other hand is a huge slab of concrete in a geological stable location - would it be the last recognisably man-made structure left on Earth thousands of years later or are there any others that could compete with this mammoth piece of engineering?
I should have thought dams would be amongst the first large things to go. They have all that water pressing on them all the time.
(bolding mine)
:dubious:
Have you ever seen Hoover Dam? That’s one, big, honkin’ hunk of concrete! 
Sure, but dams are subject to cascade (heh) failure. If you’ve ever seen footage of one failing or being brought down, the first major hole basically starts a chain reaction.
I’d think less-stressed structures like the pyramids or the Great Wall will last a lot longer than any dam. It’ll also depend on your definition of “last”.
Also, out of curiosity, why the Hoover Dam and not some other one? It’s not even in the top 20 for largest dams in the world, according to Wikipedia.
The Great Pyramids, indeed, are still in the running.
The show Life After People dealt with Hoover Dam. They estimated that the generators would stay running for about a year or so. There’s an invasive species of mollusks in the lake that would eventually clog the cooling water inlet pipes which would trip the generators as they overheated. After the generators stop, water would stop flowing through the dam and the lake behind it would rise until it reached the level of the spillways. At this point the dam would remain fairly stable. They gave it an estimated 10,000 years or so before Mother Nature finally destroyed it.
The Great Pyramids are already about half that old and will probably last significantly longer than that. All a dam has to do is spring a leak and water will quickly erode it until the rest of it falls down. The pyramids just sit there. Their pyramid shape means that they can’t just topple over. Some of the inner structures might collapse but the pyramids themselves will retain their shape for a very long time. Life After People figured that the pyramids would last so long that they would be covered with sand and protected long before they eroded away.
Life After People also predicted a long life for the Great Wall of China and Mount Rushmore.
Have you ever seen Grand Coolee Dam? It’s over 3 times as much volume. It’s not as tall, but is much longer and produces much more power.
As for why Hoover, there are many people for whom Hoover Dam is the archtypical dam. That is, it’s what they think of when you say “dam” without specifying which one… Not sure why this is, but it seems to be real common. Not everyone is that way. Here in the Portland area, many have Bonneville Dam as their archtypical dam. I grew up in the Spokane area mostly, so have a different archtypical dam (betcha can’t guess which one!)
Anyway, I figure Grand Coolee would easily outlast Hoover if both were left unattended. Hoover’s pretty, but that arch looks much less robust than GCD. GCD is basically just an artificial ridge made of concrete. However, I’m sure there are many structures more robust than either dam. Most probably don’t even have names.
The Great Wall, by the way, is mostly in ruins except for some parts kept up for the tourists.
I think it would come down to the pyramids or Mount Rushmore.
If we aren’t limiting ourselves to the Earth, but to signs of humanity in general, then moon-based objects and astronaut footprints will probably outlast both of the above. Many satellites as well.
Pyramids would be my answer too. I wouldn’t call Mt. Rushmore a “structure” per se.
Mt Rushmore is much like the Old Man of the Mountain in New Hampshire. Remember that that broke apart and collapsed into a jumble of rocks. Rushmore is going to do the same eventually. I don’t know how long that will be, though. I doubt if anyone does.
The Old Man of the Mountains was several blocks of granite resting on each other. When the bottom one finally fell the whole stack collapsed. I’m not sure Mt Rushmore is really in the same boat for modes of failure.
Yeah, too much rain/freezing at Rushmore to make it last. Sooner or later it’ll cleave.
Thought I recalled when I was at Mt Rushmore that there were issues w/ some portions of the rock being less than perfectly stable, with factors such as porosity affecting where they placed the heads. While some vague faces might last for millenia, George’s nose might drop off much sooner.
It was the show Life After People that inspired the q - Hoover Dam was specifically mentioned as it’s a solid slab of concrete (as opposed to other big dams which are earthworks) in an area which is fairly stable in climate terms and unlikely to experience any earthquakes that would inevitably be the end of many of man’s other structures, if we weren’t around to maintain them. Hoover Dam also has the best song.
Mt. Rushmore’s a good candidate, carved in solid granite. Could we expect the presidential visages to endure after Lake Mead finally wins out against Hoover Dam, or would Washington et al be eroded to hell long before then? You Americans build things to last, anyway.
On the Pyramids at Giza - how long would it take for the desert to reclaim them? The Sphinx had to be excavated, after all. Without us around to prevent it, wouldn’t the edge of the Sahara simply swamp the Pyramids (and Cairo)?
I believe in this case, the correct term is “impeach”.
Apparently the oldest building is in France and dates to 4850 BC. Seems to be in surprisingly good state, for a wall I guess.
Didn’t expect that, would have thought the oldest would be in Sumer or Mesoamerica.
Yes I have. Also the huge lake lake behind it, constantly pushing on it, and dribbling through, slowly eroding stuff. I have also seen how lots of guys work there, not doing nothing. Dams need constant maintenance if they are not going to fail, and when they fail they fail big!
I can’t help but wonder how long China’s Three Gorges Dam will last. Given what I’ve heard, you couldn’t possibly pay me enough to live anywhere downriver from it.
So if sand is covering it it hasn’t “lasted”?
I’m thinking in terms of if, say, FBI space aliens return in 10,000+ years after human extinction - what evidence of humanity would they find? If the desert has reclaimed Cairo then a lasting impression of human engineering it ain’t.