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Given that dinosaurs existed for hundres of millions of years and that we have found very few fossils, the probability of finding a fossil from a single day see

Given that dinosaurs existed for hundres of millions of years and that we have found very few fossils, the probability of finding a fossil from a single day seems incredibly small. But of course an asteroid strike may create very favorable conditions for fossilization.

sideshowb 5y ago
It's a very good point and got me wondering, how do we know the dinosaurs were killed by a single asteroid strike? What if there were many within a relatively short time scale? If you're going to answer "parsimony", what if these events aren't independent? (I'm not a paleontologist)
- morelisp 5y ago
  https://en.wikipedia.org/wiki/Cretaceous%E2%80%93Paleogene_extinction_event https://en.wikipedia.org/wiki/Cretaceous%E2%80%93Paleogene_e...
- newsclues 5y ago
  It’s a good theory, and may have occurred by large objects breaking up during atmospheric entry or it was a cluster of objects in space.
  - pfdietz 5y ago
    The K/T impactor had linear dimensions comparable to the scale height of the atmosphere. Unless the impact was at an extremely shallow angle (unlikely) breaking up in the atmosphere would have no significant effect. The mass of atmosphere that could potentially transfer momentum with the impactor before impact would be much less than the mass of the impactor.
    - pixl97 5y ago
      Wouldn't the break up be more influenced by the gravitational acceleration imparted by earth? Most asteroids are rather loosely bound.
      - ncmncm 5y ago
        That would be tidal forces. There wouldn't be enough time for that. Shoemaker-Levy orbited Jupiter for quite a while before it broke up and went in.
- mannykannot 5y ago
  Apparently, when the impact hypothesis was first presented as more than just speculation (i.e. with the iridium layer as evidence), a majority of paleontologists rejected it, preferring one based on long-term high-intensity volcanism in Asia. I believe this hypothesis still has a few proponents. The collision of comet Shoemaker-Levy with Jupiter occurred as several distinct impacts, due to gravitational disruption of the comet in a previous close encounter with the planet. Something similar is clearly possible on Earth (perhaps even gravitational dispersion of a comet passing close to the Moon just before impact?) but the Chicxulub crater is large enough to explain the extinction event by itself (unless you hew to the volcanic explanation, I suppose), so the question is whether there is any evidence for multiple impacts. As far as I know, the global distribution of the physical evidence is indicative of a single source, but not definitively so.
  - pfdietz 5y ago
    At that point, they didn't even believe the volcanism hypothesis, the bias toward gradualism was so profound.
gorgoiler 5y ago
The Tanis death assemblage contains land and river life mixed together with large amounts of mud — mud which is made partly of molten rock granules. The hypothesis is that it was formed from the rapid drainage of a flooded plain, and that the flood was probably caused by the Chicxulub event.
- drewrv 5y ago
  Thanks for posting this. I didn’t know about it and it’s lead me down quite the Wikipedia rabbit hole.
  - stevenwoo 4y ago
    The 90 minute documentary mentioned in the article aired this week, has the real fossils mixed with animations of the creatures and coverage of the excavation you may enjoy (Dinosaurs: The Final Day).
- deleted 5y ago
  [deleted]
- ncmncm 5y ago
  It also has salt-water fish mixed up with fresh-water fish.
newsclues 5y ago
I think if something lived for millions of years, and impacts on earth are not uncommon, it was bound to happen at some point. On a long enough timeline, improbable events are expected.
- sideshowb 5y ago
  I don't think gp was questioning that, so much as the likelihood of finding more than one fossil from the same event, given all the times we could have found fossils from.
  - justsid 5y ago
    Wouldn’t this single event have a super high chance of generating fossils though giving that a) it wiped out a ton of life in one go and b) it released a huge amount of debris ready to cover things up nicely and preserve them?
    - ncmncm 5y ago
      Yes. What was incredibly lucky was the fossil stratum being exposed again at a time when we could spot them. There must be megatons more of this stuff, wholly inaccessible.
BlueTemplar 5y ago
Not even single day, single hour ! (Violent water sloshing mixing marine, freshwater and land life caused by seismic waves rather than the "direct" tsunami.)

sideshowb 5y ago

It's a very good point and got me wondering, how do we know the dinosaurs were killed by a single asteroid strike? What if there were many within a relatively short time scale? If you're going to answer "parsimony", what if these events aren't independent? (I'm not a paleontologist)

morelisp 5y ago
https://en.wikipedia.org/wiki/Cretaceous%E2%80%93Paleogene_extinction_event https://en.wikipedia.org/wiki/Cretaceous%E2%80%93Paleogene_e...
newsclues 5y ago
It’s a good theory, and may have occurred by large objects breaking up during atmospheric entry or it was a cluster of objects in space.
- pfdietz 5y ago
  The K/T impactor had linear dimensions comparable to the scale height of the atmosphere. Unless the impact was at an extremely shallow angle (unlikely) breaking up in the atmosphere would have no significant effect. The mass of atmosphere that could potentially transfer momentum with the impactor before impact would be much less than the mass of the impactor.
  - pixl97 5y ago
    Wouldn't the break up be more influenced by the gravitational acceleration imparted by earth? Most asteroids are rather loosely bound.
    - ncmncm 5y ago
      That would be tidal forces. There wouldn't be enough time for that. Shoemaker-Levy orbited Jupiter for quite a while before it broke up and went in.
mannykannot 5y ago
Apparently, when the impact hypothesis was first presented as more than just speculation (i.e. with the iridium layer as evidence), a majority of paleontologists rejected it, preferring one based on long-term high-intensity volcanism in Asia. I believe this hypothesis still has a few proponents. The collision of comet Shoemaker-Levy with Jupiter occurred as several distinct impacts, due to gravitational disruption of the comet in a previous close encounter with the planet. Something similar is clearly possible on Earth (perhaps even gravitational dispersion of a comet passing close to the Moon just before impact?) but the Chicxulub crater is large enough to explain the extinction event by itself (unless you hew to the volcanic explanation, I suppose), so the question is whether there is any evidence for multiple impacts. As far as I know, the global distribution of the physical evidence is indicative of a single source, but not definitively so.
- pfdietz 5y ago
  At that point, they didn't even believe the volcanism hypothesis, the bias toward gradualism was so profound.

gorgoiler 5y ago

The Tanis death assemblage contains land and river life mixed together with large amounts of mud — mud which is made partly of molten rock granules. The hypothesis is that it was formed from the rapid drainage of a flooded plain, and that the flood was probably caused by the Chicxulub event.

drewrv 5y ago
Thanks for posting this. I didn’t know about it and it’s lead me down quite the Wikipedia rabbit hole.
- stevenwoo 4y ago
  The 90 minute documentary mentioned in the article aired this week, has the real fossils mixed with animations of the creatures and coverage of the excavation you may enjoy (Dinosaurs: The Final Day).
deleted 5y ago
[deleted]
ncmncm 5y ago
It also has salt-water fish mixed up with fresh-water fish.

newsclues 5y ago

I think if something lived for millions of years, and impacts on earth are not uncommon, it was bound to happen at some point. On a long enough timeline, improbable events are expected.

sideshowb 5y ago
I don't think gp was questioning that, so much as the likelihood of finding more than one fossil from the same event, given all the times we could have found fossils from.
- justsid 5y ago
  Wouldn’t this single event have a super high chance of generating fossils though giving that a) it wiped out a ton of life in one go and b) it released a huge amount of debris ready to cover things up nicely and preserve them?
  - ncmncm 5y ago
    Yes. What was incredibly lucky was the fossil stratum being exposed again at a time when we could spot them. There must be megatons more of this stuff, wholly inaccessible.

BlueTemplar 5y ago

Not even single day, single hour ! (Violent water sloshing mixing marine, freshwater and land life caused by seismic waves rather than the "direct" tsunami.)