9 ms·

A fifth of Earth’s geologic history might have vanished because of glaciers

183 points by gricardo99 8y ago

captainperl 8y ago
One of the most interesting geology articles I've ever read.
jaapaap 8y ago
One of the most interesting comments I've ever read
stareatgoats 8y ago
Kudos to real scientists who bit by bit uncovers what happened in earths past, in ever-increasing resolution. Whether "snowball earth" is accurate or not, what appears in outline is an earth that would have been uninhabitable for humans under most of, and even in relative recent, geological history. It begs the question of how we might deal with the situation where the globe once again becomes uninhabitable (if we survive that long): terraforming or cocooning. The latter seems the best bet.
- craigsmansion 8y ago
  Or maybe even more tantalising, how did the previous sentient species deal with it. Or to reverse that question, is there something a hypothetical species, akin to our own, could have constructed that could have withstood Snowball Earth ? :) It sounds easy enough, objects in space, large structures, unnatural concentrations of radioactive materials, sure, but over millions of years with kilometers of the top crust simply shaved off and recycled through the core of the planet? It's amusing our notion of "glacial" loses meaning over such time-spans. How can it do anything, since glaciers just lie there. But over millions of years, it's a high-speed efficient grinding machine the size of a planet. Conversely, as to how we might deal with the situation, ludicrous though it might seem with our advances and technology, maybe we simply can't. Even a passive beacon on the moon which wouldn't have suffered from Snowball Moon; it seems plausible enough, but it has to withstand at least 250 million years of the moon's night/day cycles. Is there something we could build right now that could withstand that? Maybe? Probably? But for now I'm content the Snowball Earth hypothesis spices up a lot of Lovecraft stories. "And with strange aeons even death may die” indeed.
  - avereveard 8y ago
    Even things on dead planet like the moon can't survive indefinitely because meteors either striking it or dusting it, even if we etched the moon with nuclear blasts contour would get fuzzy and disappear over million years. One option would be to put in one Lagrange point some high quantity of radioactive material. You'd need to pick quantity and material well tho, because material with short hair life would cool off to get and become just a rock and materials with too long half life would be very hard to detect due their low emissions. Give it a shape nature would have had time to replicate like an empty cylinder and it would likely be the best way to leave artifact for million years into the future. Won't be able to store any meaningful information beyond "someone was here" and future people coming to bertrand teapot style of argumentation against God would have a hell of a shock upon rediscovery
    - ajross 8y ago
      Almost all of the moon's surface is older than the ~500MYA scale we're talking about. It has the occasional impact, like Earth does, but the overwhelming majority of those craters you see are from the early bombardment. The dark splotches visible on the near side, the maria, are mostly flat volcanic plains laid down toward the end of that period about 3BYA, and are visibly lacking in craters. No, a base on the moon would still be there.
      - Retric 8y ago
        That’s the large impacts. The Moon gets hit by ~2800 kg of meteor material per day, though this likely has been decreasing over time. It’s about one ‘bullet’ going ~38,000 mph per 379 square kilometers. But times 365 days a year you’re at 1 bullet per square km/year. Over 500 million years that’s 500 bullets per square meter which would heavily damage if not outright destroy any structure and cover it in lunar dust. PS: The 38,000 mph issue is hard to conceive of assuming similar weight it’s ~2,500 times the kinetic energy of a 9mm bullet. Military rail guns are aiming for Mach 7+ which is ~1/40 the kenetic energy of a similarly massed meteor.
        8y ago
hirundo 8y ago
Could an advanced species / civilization have risen and fallen during this period, leaving no trace?
- stestagg 8y ago
  What if, by unbalancing the worlds ecology, said civilisation triggered that ice-age?
  - stareatgoats 8y ago
    What evidence do you have that there is some such thing as a "balanced world ecology" at all? It seems to me that all the evidence, in addition to logic, is in the opposite direction.
    - erikpukinskis 8y ago
      I guess I share your problem, I’m not sure “balanced” is the right word. You could have two species, a single celled animal and a single celled plant and ostensibly that would be “balance”. Maybe a better word for what is at risk is “diversity”. At this time there are still wild ecologies with incredible diversity in all three phases of water on Earth, the frozen, the liquid, and the steamy. And there are also partly dead places. The American Midwest is largely ecologically dead, although we know before the European settlers came there was stable soil and incredible biodiversity there. But balance and biodiversity are connected. In a diverse ecology, you can remove any species, or turn any dial slightly, metabolism will dip, and then roar back into full power because there is so much latent genetic material in the ecology ready to go. That’s been destroyed in a place like the Midwest. If you stop putting oil into that ecology, the metabolism would plummet, and it would take a million years to return to anything close to what it was before European settlers. In a so-called “balanced” ecology, metabolism would rebound on a scale of decades or even seasons. The moral assumption underlying this is that the most metabolism per square foot of solar energy is the most good.
      - stareatgoats 8y ago
jl6 8y ago
Wow, I always assumed that complex life prior to our own was unlikely because it would have left a trace that we could detect. But if there is a plausible mechanism by which all such traces would have been erased, then who knows what might have happened deep in those billions of years when supposedly only single-celled life existed? Perhaps Earth’s previous inhabitants triggered runaway global cooling, effectively hitting the reset switch back to single-celled life. Perhaps they escaped to Venus and vowed not to let the same thing happen there, but got it wrong in the other direction.
- rjf72 8y ago
  I'd be hesitant to attribute any sort of hypothetical causes, but it's fun to also consider such scenarios when thinking just one rock a bit further out. Mars was at one time a warm, watery planet not dissimilar to Earth. It's going to be extremely interesting once we get feet on the ground and can start really digging into the planet's past, quite literally. Most tantalizing of course is that it seems to have had all that was necessary to see the development of life. In many ways even finding absolutely no evidence of life at all will be as exciting as finding the opposite. Okay definitely not as exciting, but it'd certainly be really quite interesting!
- erikpukinskis 8y ago
  Even on shorter timescales, there are 100+ ton milled monoliths all over the world, which are seemingly 4000+ years years old. Yet the civilizations of 4000 years ago don’t seem to have known how to mill such stones. It probably wasn’t until the 19th century at the earliest that we “re-learned” the basic skills required. My default assumption is that history has only picked up, at best, the latter cycles on big time scales.
  - zilian 8y ago
    Do you have sources for those claims ?
    - erikpukinskis 8y ago
      I just watch a lot of Brian Foerster videos on YouTube e.g. https://youtu.be/AGBOf8mrWjs https://youtu.be/AGBOf8mrWjs Baalbek is a good place to see 1000+ ton milled stones: https://youtu.be/jo-oEk8itlo https://youtu.be/jo-oEk8itlo Cuzco also seems to have some pre-Inca constructions that can’t be explained: https://youtu.be/66x9VLwZaDQ https://youtu.be/66x9VLwZaDQ
aerophilic 8y ago
I find the use of zircons in this context very interesting. Starting with the Wikipedia article: https://en.m.wikipedia.org/wiki/Zircon https://en.m.wikipedia.org/wiki/Zircon I went down the rabbit hole and learned a bit about Geochronology: https://en.m.wikipedia.org/wiki/Geochronology https://en.m.wikipedia.org/wiki/Geochronology It is interesting how they “break up” dating depending on the time frame, for example some dating is only measured by “eon” (half a billion years), whereas the “finest” measurement seems to be “age” which corresponds to single digit millions of years. A bit humbling to think that all of humanity can “fit” in the smallest geological measure of time.
- cbkeller 8y ago
  Yeah, I think the vastness of geologic time has been aptly described as "geology’s signal contribution to human thought" -- the same way astronomy showed us we weren't the literal center of the universe. I think about Myr and Gyr timescales every day at work, but it's still hard to really intuitively grasp. Obligatory John McPhee: > Numbers do not seem to work well with regard to deep time. Any number above a couple of thousand years—fifty thousand, fifty million—will with nearly equal effect awe the imagination. > Consider the earth’s history as the old measure of the English yard, the distance from the king’s nose to the tip of his outstretched hand. One stroke of a nail file on his middle finger erases human history.
hoorayimhelping 8y ago
So does this imply that we'll never know if the Cambrian Explosion is actually an explosion or just a continuation from a previously unrecoverable geological record? Is it even possible to have complex multicellular life under snowball earth conditions? >Although it’s likely down to a number of factors, one possibility is that Snowball Earth’s erosion was so significant that there wasn’t much topography left to erode when all was said and done. The planet simply needed to forge more land first, and that takes time. The balance of earth is so interesting. The process that forges new land (volcanism) is the same process that beats back snowball earth and re-balances the atmosphere with more CO2. It's a bit old and cheesy, some of the info might be outdated, but this is a great episode on this topic: https://www.youtube.com/watch?v=XEiu611KsUo https://www.youtube.com/watch?v=XEiu611KsUo
- mannykannot 8y ago
  > The process that forges new land (volcanism) is the same process that beats back snowball earth and re-balances the atmosphere with more CO2. And I believe volcanism, at least the sort that is most common today (that from ocean-margin subduction zones, rather than that from spreading zones like Iceland or hotspots like Hawaii) results from subducted sediments melting into magma, with their melting points reduced by the presence of subducted water. If so, then do we have the large amounts of sediment, created by the snowball-earth glaciation, setting the stage for the volcanism that ends it? There are fossils of Precambrian, post-snowball multi-cellular life, but they are not very much like, and nowhere near as diverse, as what appeared in the Cambrian, so I think the explosion still looks like a real event and not just an artifact of an imperfect record. http://www.ucmp.berkeley.edu/vendian/ediacaran.php http://www.ucmp.berkeley.edu/vendian/ediacaran.php
- hedora 8y ago
  Ph'nglui mglw'nafh Cthulhu R'lyeh wgah'nagl fhtagn! [0] Since the erased part of the geological record starts 100’s of millions of years before the climate event that froze everything, do we even know that some earlier civilization didn’t force the climate off balance with e.g. greenhouse gasses, which ended up obliterating all multicellular organisms, and wiping the geological evidence? Other recent news about ocean current disruptions, and methane melting feedback loops in the artic suggest we might be headed that way too... [0] https://en.m.wikipedia.org/wiki/R%27lyeh https://en.m.wikipedia.org/wiki/R%27lyeh
ajmurmann 8y ago
It's interesting how most comments here immediately see this gap in our history book of Earth as a potential time span during which another advanced civilization could have developed and gone extinct (my mind did the same). Meanwhile the article without much discussion jumps to this: "complex life first emerged when Snowball Earth’s monstrous mealtime came to an end."
lostmsu 8y ago
TL;DR; Earth appears to have been covered by miles deep ice for many hundred millions of years during the last billion, and that caused normal geological leftovers of the period to be nonexistent. The best info for that period is stuff frozen into zircon crystals, which scientists think supports the ice hypothesis.

183 points by gricardo99 8y ago

captainperl 8y ago

One of the most interesting geology articles I've ever read.

jaapaap 8y ago

One of the most interesting comments I've ever read

stareatgoats 8y ago

Kudos to real scientists who bit by bit uncovers what happened in earths past, in ever-increasing resolution. Whether "snowball earth" is accurate or not, what appears in outline is an earth that would have been uninhabitable for humans under most of, and even in relative recent, geological history. It begs the question of how we might deal with the situation where the globe once again becomes uninhabitable (if we survive that long): terraforming or cocooning. The latter seems the best bet.

craigsmansion 8y ago
Or maybe even more tantalising, how did the previous sentient species deal with it. Or to reverse that question, is there something a hypothetical species, akin to our own, could have constructed that could have withstood Snowball Earth ? :) It sounds easy enough, objects in space, large structures, unnatural concentrations of radioactive materials, sure, but over millions of years with kilometers of the top crust simply shaved off and recycled through the core of the planet? It's amusing our notion of "glacial" loses meaning over such time-spans. How can it do anything, since glaciers just lie there. But over millions of years, it's a high-speed efficient grinding machine the size of a planet. Conversely, as to how we might deal with the situation, ludicrous though it might seem with our advances and technology, maybe we simply can't. Even a passive beacon on the moon which wouldn't have suffered from Snowball Moon; it seems plausible enough, but it has to withstand at least 250 million years of the moon's night/day cycles. Is there something we could build right now that could withstand that? Maybe? Probably? But for now I'm content the Snowball Earth hypothesis spices up a lot of Lovecraft stories. "And with strange aeons even death may die” indeed.
- avereveard 8y ago
  Even things on dead planet like the moon can't survive indefinitely because meteors either striking it or dusting it, even if we etched the moon with nuclear blasts contour would get fuzzy and disappear over million years. One option would be to put in one Lagrange point some high quantity of radioactive material. You'd need to pick quantity and material well tho, because material with short hair life would cool off to get and become just a rock and materials with too long half life would be very hard to detect due their low emissions. Give it a shape nature would have had time to replicate like an empty cylinder and it would likely be the best way to leave artifact for million years into the future. Won't be able to store any meaningful information beyond "someone was here" and future people coming to bertrand teapot style of argumentation against God would have a hell of a shock upon rediscovery
  - ajross 8y ago
    Almost all of the moon's surface is older than the ~500MYA scale we're talking about. It has the occasional impact, like Earth does, but the overwhelming majority of those craters you see are from the early bombardment. The dark splotches visible on the near side, the maria, are mostly flat volcanic plains laid down toward the end of that period about 3BYA, and are visibly lacking in craters. No, a base on the moon would still be there.
    - Retric 8y ago
      That’s the large impacts. The Moon gets hit by ~2800 kg of meteor material per day, though this likely has been decreasing over time. It’s about one ‘bullet’ going ~38,000 mph per 379 square kilometers. But times 365 days a year you’re at 1 bullet per square km/year. Over 500 million years that’s 500 bullets per square meter which would heavily damage if not outright destroy any structure and cover it in lunar dust. PS: The 38,000 mph issue is hard to conceive of assuming similar weight it’s ~2,500 times the kinetic energy of a 9mm bullet. Military rail guns are aiming for Mach 7+ which is ~1/40 the kenetic energy of a similarly massed meteor.
      - 8y ago

hirundo 8y ago

Could an advanced species / civilization have risen and fallen during this period, leaving no trace?

stestagg 8y ago
What if, by unbalancing the worlds ecology, said civilisation triggered that ice-age?
- stareatgoats 8y ago
  What evidence do you have that there is some such thing as a "balanced world ecology" at all? It seems to me that all the evidence, in addition to logic, is in the opposite direction.
  - erikpukinskis 8y ago
    I guess I share your problem, I’m not sure “balanced” is the right word. You could have two species, a single celled animal and a single celled plant and ostensibly that would be “balance”. Maybe a better word for what is at risk is “diversity”. At this time there are still wild ecologies with incredible diversity in all three phases of water on Earth, the frozen, the liquid, and the steamy. And there are also partly dead places. The American Midwest is largely ecologically dead, although we know before the European settlers came there was stable soil and incredible biodiversity there. But balance and biodiversity are connected. In a diverse ecology, you can remove any species, or turn any dial slightly, metabolism will dip, and then roar back into full power because there is so much latent genetic material in the ecology ready to go. That’s been destroyed in a place like the Midwest. If you stop putting oil into that ecology, the metabolism would plummet, and it would take a million years to return to anything close to what it was before European settlers. In a so-called “balanced” ecology, metabolism would rebound on a scale of decades or even seasons. The moral assumption underlying this is that the most metabolism per square foot of solar energy is the most good.
    - stareatgoats 8y ago

jl6 8y ago

Wow, I always assumed that complex life prior to our own was unlikely because it would have left a trace that we could detect. But if there is a plausible mechanism by which all such traces would have been erased, then who knows what might have happened deep in those billions of years when supposedly only single-celled life existed? Perhaps Earth’s previous inhabitants triggered runaway global cooling, effectively hitting the reset switch back to single-celled life. Perhaps they escaped to Venus and vowed not to let the same thing happen there, but got it wrong in the other direction.

rjf72 8y ago
I'd be hesitant to attribute any sort of hypothetical causes, but it's fun to also consider such scenarios when thinking just one rock a bit further out. Mars was at one time a warm, watery planet not dissimilar to Earth. It's going to be extremely interesting once we get feet on the ground and can start really digging into the planet's past, quite literally. Most tantalizing of course is that it seems to have had all that was necessary to see the development of life. In many ways even finding absolutely no evidence of life at all will be as exciting as finding the opposite. Okay definitely not as exciting, but it'd certainly be really quite interesting!
erikpukinskis 8y ago
Even on shorter timescales, there are 100+ ton milled monoliths all over the world, which are seemingly 4000+ years years old. Yet the civilizations of 4000 years ago don’t seem to have known how to mill such stones. It probably wasn’t until the 19th century at the earliest that we “re-learned” the basic skills required. My default assumption is that history has only picked up, at best, the latter cycles on big time scales.
- zilian 8y ago
  Do you have sources for those claims ?
  - erikpukinskis 8y ago
    I just watch a lot of Brian Foerster videos on YouTube e.g. https://youtu.be/AGBOf8mrWjs https://youtu.be/AGBOf8mrWjs Baalbek is a good place to see 1000+ ton milled stones: https://youtu.be/jo-oEk8itlo https://youtu.be/jo-oEk8itlo Cuzco also seems to have some pre-Inca constructions that can’t be explained: https://youtu.be/66x9VLwZaDQ https://youtu.be/66x9VLwZaDQ

aerophilic 8y ago

I find the use of zircons in this context very interesting. Starting with the Wikipedia article: https://en.m.wikipedia.org/wiki/Zircon https://en.m.wikipedia.org/wiki/Zircon I went down the rabbit hole and learned a bit about Geochronology: https://en.m.wikipedia.org/wiki/Geochronology https://en.m.wikipedia.org/wiki/Geochronology It is interesting how they “break up” dating depending on the time frame, for example some dating is only measured by “eon” (half a billion years), whereas the “finest” measurement seems to be “age” which corresponds to single digit millions of years. A bit humbling to think that all of humanity can “fit” in the smallest geological measure of time.

cbkeller 8y ago
Yeah, I think the vastness of geologic time has been aptly described as "geology’s signal contribution to human thought" -- the same way astronomy showed us we weren't the literal center of the universe. I think about Myr and Gyr timescales every day at work, but it's still hard to really intuitively grasp. Obligatory John McPhee: > Numbers do not seem to work well with regard to deep time. Any number above a couple of thousand years—fifty thousand, fifty million—will with nearly equal effect awe the imagination. > Consider the earth’s history as the old measure of the English yard, the distance from the king’s nose to the tip of his outstretched hand. One stroke of a nail file on his middle finger erases human history.

hoorayimhelping 8y ago

So does this imply that we'll never know if the Cambrian Explosion is actually an explosion or just a continuation from a previously unrecoverable geological record? Is it even possible to have complex multicellular life under snowball earth conditions? >Although it’s likely down to a number of factors, one possibility is that Snowball Earth’s erosion was so significant that there wasn’t much topography left to erode when all was said and done. The planet simply needed to forge more land first, and that takes time. The balance of earth is so interesting. The process that forges new land (volcanism) is the same process that beats back snowball earth and re-balances the atmosphere with more CO2. It's a bit old and cheesy, some of the info might be outdated, but this is a great episode on this topic: https://www.youtube.com/watch?v=XEiu611KsUo https://www.youtube.com/watch?v=XEiu611KsUo

mannykannot 8y ago
> The process that forges new land (volcanism) is the same process that beats back snowball earth and re-balances the atmosphere with more CO2. And I believe volcanism, at least the sort that is most common today (that from ocean-margin subduction zones, rather than that from spreading zones like Iceland or hotspots like Hawaii) results from subducted sediments melting into magma, with their melting points reduced by the presence of subducted water. If so, then do we have the large amounts of sediment, created by the snowball-earth glaciation, setting the stage for the volcanism that ends it? There are fossils of Precambrian, post-snowball multi-cellular life, but they are not very much like, and nowhere near as diverse, as what appeared in the Cambrian, so I think the explosion still looks like a real event and not just an artifact of an imperfect record. http://www.ucmp.berkeley.edu/vendian/ediacaran.php http://www.ucmp.berkeley.edu/vendian/ediacaran.php
hedora 8y ago
Ph'nglui mglw'nafh Cthulhu R'lyeh wgah'nagl fhtagn! [0] Since the erased part of the geological record starts 100’s of millions of years before the climate event that froze everything, do we even know that some earlier civilization didn’t force the climate off balance with e.g. greenhouse gasses, which ended up obliterating all multicellular organisms, and wiping the geological evidence? Other recent news about ocean current disruptions, and methane melting feedback loops in the artic suggest we might be headed that way too... [0] https://en.m.wikipedia.org/wiki/R%27lyeh https://en.m.wikipedia.org/wiki/R%27lyeh

ajmurmann 8y ago

It's interesting how most comments here immediately see this gap in our history book of Earth as a potential time span during which another advanced civilization could have developed and gone extinct (my mind did the same). Meanwhile the article without much discussion jumps to this: "complex life first emerged when Snowball Earth’s monstrous mealtime came to an end."

lostmsu 8y ago

TL;DR; Earth appears to have been covered by miles deep ice for many hundred millions of years during the last billion, and that caused normal geological leftovers of the period to be nonexistent. The best info for that period is stuff frozen into zircon crystals, which scientists think supports the ice hypothesis.