I understand that high-level nuclear waste must be kept isolated for a a quarter million years. I would like some help envisioning that.
I think we can agree that a quarter million years in evolution is nothing at all, right? On the other hand human civilization is about seven thousand years old, so a quarter million years is a lot by that measure. How about in plate tectonics? How old are mountains and stuff?
Can anyone help me understand how long this is?
Nuclear waste warning signs are designed (or hoped) to be effective for 10,000 years (Long-term nuclear waste warning messages - Wikipedia) - a long time, but a lot shorter than 250,000. A quarter million years is a moderately long time in evolution - a lot of species survive only a million years. For mountains, though, 250,000 years is pretty short - Everest is a young mountain at 60 million years - the Appalachians are closer to 300 million years old.
It’s not nothing in evolutionary terms. 250,000 years ago there were no domestic dogs, nor any other domesticated animals. Homo Sapiens had a wide range of dates for possible emergence, 250,000 is at the lowest end of that range, though now looking at 350,000 - 500,000 years ago.
Going back from the present its two and a bit ice ages.
Depending on where you were on the planet you may have seen everything you know ground down to bare rock by kilometre-thick glaciers coming and going - twice, sea level dropping a hundred metres or more and shorelines retreating tns of kilometres, vegetation going from lush forest to tundra and a whole lot of other massive changes that would have rendered your familiar world unrecognisable.
The last glacial maximum was about 18,000 years ago, so we might have 80,000 years before we see that again, but you might see it twice again in your time scale.
250k years ago was the Middle Pleistocene (781k to 126k ago), and is REALLY recent in terms of geological time. It’s quaternary period, and for the most part, any stratigraphic layers that are from the Quaternary are stuff like river sediments from extant rivers and the like. In large part, the “new” stuff out there is Cretaceous era stuff. Probably the biggest thing going on 250k years ago was the ongoing Ice Age glaciation.
Evolutionarily, there were Homo Heidelbergensis (archaic humans) and Neanderthals, but anatomically modern humans weren’t around just yet.
As far as looking 250k years ahead, I’d imagine that geologists can probably predict with some reasonable accuracy what will happen, kind of like short-term weather forecasting. But in human terms, any nuclear waste probably needs to be stored in a location where it can be safely forgotten about- I imagine one of two things happening- either we continue on our current path and end up a very technologically advanced species and remember where the waste is, and avoid it. Or we have some sort of technological dark age and/or cataclysm and we forget where it is.
To me, that means that we need to find a site with a few prerequisites: A) Somewhere remote on the surface- it’s not likely that in 250k years, today’s deserts are going to become forests or vice-versa. B) Somewhere NOT near anything that could be usefully mined. You don’t want some coal miners from 100k years from now stumbling onto our nuclear waste repository by accident. C) Somewhere geologically stable enough that natural processes (earthquakes, volcanism, floods, glaciers, etc…) are going to disturb the waste and introduce it into the environment. And finally D) Somewhere that is palatable to the people living nearby, or where the local government can ignore the locals.
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ninja’d by better posts
The youngest mountains are generally considered to be … what’s the time again? There are mountains currently being pushed higher so how do you date them? Plus, volcanoes are mountains.
If you’re asking what’s the most recent orogeny (mountain range building) to kick off, I don’t know for certain, but I do know the Pasadena Orogeny in the Western US is in around the middle Pleistocene range (say 1-2 Ma.) By comparison, New Zealand’s Kaikoura Orogeny (Southern Alps) began 25 Ma and the Himalayas started 40-50 Ma.
Due to plate tectonics, Europe would have been around 7.5 km (4.7 miles) closer to North America. Your fingernails would, hypothetically, have grown by around the same length.
One of many very useful milestones. Thank you very much.
The Grand Canyon gives some intuition for the scale of geologic/evolutionary time. It took just a few million years to erode, the same order of magnitude as the time since humans diverged from chimps. The Earth is about 1,000 times older.
If I remember correctly, islands in the Hawaiian chain have a life span of about 20 to 30 million years. A quarter of a million years is about one percent of that. Since the big extinction that killed most dinosaurs, there’s been two full cycles of Hawaiian islands.
There’s a third possibility: we become so technologically advanced that the waste becomes a resource, so it’s mined for useful heavy metals/radioactives.
Unfortunately, we seem to be the kind of species that can be pretty technologically advanced and still forget where we put radioactive stuff Uranium Ore Stored At Grand Canyon Park Museum May Or May Not Pose Health Risk : NPR
“For many years, three buckets full of uranium ore sat in a museum building at the South Rim of Grand Canyon National Park. Tours often visited the museum collection building, with children on tours sitting next to the buckets for a half-hour.”
250,000 years in natural selection isn’t really a long term.
250,000 years of selective breeding though? There will be huge differences. I believe most breeds of dogs were only bred in the last 150 years.
Also 250,000 years is a virtual infinity regarding human technological evolution (in a post industrial society I mean).
But on universal scales, its a rounding error. For evolution its not a huge time period either.
All in all, these comparisons seem very encouraging. Once you put the waste into the geology realm, you got it licked. Find someplace dry and stable, dig down three or four hundred meters, pop it in and seal it up.
This is an area I enjoy reading in.
Some of the work I’ve really enjoyed, found provocative and would recommend are:
Jan Zalasiewicz - The Earth after us: what legacy will humans leave in the rocks?
He’s a geologist and heavily involved in the movement to decide if the Anthropocene is a thing, nd has done a lot of very accessible writing about that aspect of long-term human and geological scales of time.
Life after People - documentary series - mainly focussed on what happens to ecology and infrastructure if humans suddenly disappeared. Probably focussed a bit short of your preferred time-frame.
The future is Wild tv series - speculates on evolution into the future, but looks at multi-million year time-scales.
Greg Benford, Deep time: how humanity communicates across millenia - good overview of precisely the sorts of issue raised by OP.
My attempt at providing something that could help envision it: There are about as many days in 250,000 years (about 91 million) as there are seconds in three years.
Even if that were to happen, it’s a really narrow gap in our history between (1) deep mines for resources that could potentially encounter buried nuclear waste and (2) discovery of fission and thus geiger counters and other similar instruments able to detect it.
That is, miners after the 1950s and thereafter would just detect nuclear waste with their instruments when they encountered it, before too much harm was done. Yucca mountain is 1000 feet down - how many mines were dug in the pre fission era that deep?