Dinosaurs Not Killed By Blast -- But By Acid Rain?
Posted by
Hemos
on from the flip-flop-flip-flop dept.
JCMay writes "FoxNews is reporting that it wasn't just the impact of a ten-mile wide asateroid in Mexico that killed off the dinosaurs, but rather the chemicals kicked up-- mostly carbon dioxide and many sulfur-bearing compounds."
Re:problem with this theory
by
bcrowell
·
· Score: 3
A standard argument against the giant impact theory of the extinction was always that certain critters, e.g. dinosaurs, went extinct, while others, e.g. reptiles, didn't. Same thing with plankton -- some bought the farm, but other very similar species survived.
The evidence is very strong that there was a giant impact, but it doesn't completely explain the pattern of extinctions. However, there was an interesting recent case where someone studied the area around a volcano that had erupted (was it Mt. St. Helens??) and found that it was surprisingly random what plants got the first toeholds in the newly sterilized area.
People who disbelieve the giant impact explanation say it's straightforward: a crocodilian species and a dinosaur species might have been competing in the same ecological niche. One won, the other lost.
If this theory were true, wouldn't that mean that many other organisms other than the dinosaurs were killed? I mean, the article talks about highly toxis "globs" of sulfuric acid throughout the atmosphere. I strongly doubt anything more complicated that certain prokaryotes could survive that!
I guess it's all a matter of how concentrated the toxins are and how robust different parts of the ecology are. Kill off all the green plants, and the whole animal food chain gets pretty much destroyed. Then new plants grow from seed.
The FOX reporting here looks garbled - they say something about comparing it to the large Sudbury impact, and that Sudbury was formed by a high-velocity comet while the Chicxulub (sp?) crater was formed by an asteroid - however doesn't Sudbury have a huge quantity of asteroidal metals (it provides most of the world's nickel supply, for example)? I didn't think that's what comets were supposed to be made of... So did they just get these switched and it was actually a comet that killed the dinosaurs? Does anybody have any more links/references on this finding?
Re:Q. Summary of extinction theories?
by
Random+Utinni
·
· Score: 2
/. theories aside, here's what I remember from my paleo classes...
Asteroid impact... this has been a favorite since Alvarez found the Iridium layer. The theory goes that ~65 million years ago, a massive asteroid impacted, somewhere around the Carribean. From there, the theory fragments; some go for nuclear winter, others go for acid rain and worldwide forest-fires.
There's lots of evidence that there was in fact an asteroid impact, but there's also a lot of evidence that the results were nowhere near as bad as everyone claims. Soil samples don't suggest acid rain, nor ice age. Most importantly, the fossil record doesn't support this. What everyone forgets is that the dinosaurs didn't die in a week. Think about it, if an asteroid did all the work, you'd expect there to be a colossal slaughter, but we don't see that in the record...
Plants became poisonous and killed off dinosaurs... too many issues with this theory.
Mass migration moved diseases around which killed the dinos. This wouldn't be enough to remove them all, but it's got some good points: it would target large mobile critters more, and a disease would be more likely to affect similar animals (like dinos) but exclude others. Still, there are issues here...
Deccan Traps. When India slammed into the Asian continent, it pushed up the Himalayas, and created lava flows that covered millions of square acres. The amount of ejecta from the eruptions could have created a nuclear winter on its own (think St. Helens but millions of times worse).
No one really knows what killed off the dinosaurs, but to say that the asteroid did it itself is ridiculous. It's simply not supported. The dinosaurs were dying off for millions of years; The Cretaceous period started with really high species (dinosaur) diversity... by the end, there were pretty much two species left: T-Rex and Triceratops... the duckbills, the other Ceratopsians, etc, were almost extinct already.
Most likely it was a combination of many of these things... Diseases start to ravage certain lineages, others can't compete with new types of plants, and slowly die off. The climate changes due to massive volcanic eruptions, and this adds more challenges to various species. After a few million years of this, dinosaurs as a class are hurting: they have little species diversity left, and are unlikely to recover. An asteroid impact puts the final touch on it...
For more reading check the following links:
A Cowen Essay posted on UCMP Summaries from UCMP
Also, see The Dinosaur Heresies by Robert Bakker... His ideas are interesting and opposite of much of UCMP's thoughts. But he's definitely worth reading; I recommend this to anyone interested in dinos...
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The evidence is very strong that there was a giant impact, but it doesn't completely explain the pattern of extinctions. However, there was an interesting recent case where someone studied the area around a volcano that had erupted (was it Mt. St. Helens??) and found that it was surprisingly random what plants got the first toeholds in the newly sterilized area.
People who disbelieve the giant impact explanation say it's straightforward: a crocodilian species and a dinosaur species might have been competing in the same ecological niche. One won, the other lost.
If this theory were true, wouldn't that mean that many other organisms other than the dinosaurs were killed? I mean, the article talks about highly toxis "globs" of sulfuric acid throughout the atmosphere. I strongly doubt anything more complicated that certain prokaryotes could survive that!
I guess it's all a matter of how concentrated the toxins are and how robust different parts of the ecology are. Kill off all the green plants, and the whole animal food chain gets pretty much destroyed. Then new plants grow from seed.
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The FOX reporting here looks garbled - they say something about comparing it to the large Sudbury impact, and that Sudbury was formed by a high-velocity comet while the Chicxulub (sp?) crater was formed by an asteroid - however doesn't Sudbury have a huge quantity of asteroidal metals (it provides most of the world's nickel supply, for example)? I didn't think that's what comets were supposed to be made of... So did they just get these switched and it was actually a comet that killed the dinosaurs? Does anybody have any more links/references on this finding?
Energy: time to change the picture.
- Asteroid impact... this has been a favorite since Alvarez found the Iridium layer. The theory goes that ~65 million years ago, a massive asteroid impacted, somewhere around the Carribean. From there, the theory fragments; some go for nuclear winter, others go for acid rain and worldwide forest-fires.
There's lots of evidence that there was in fact an asteroid impact, but there's also a lot of evidence that the results were nowhere near as bad as everyone claims. Soil samples don't suggest acid rain, nor ice age. Most importantly, the fossil record doesn't support this. What everyone forgets is that the dinosaurs didn't die in a week. Think about it, if an asteroid did all the work, you'd expect there to be a colossal slaughter, but we don't see that in the record...
- Plants became poisonous and killed off dinosaurs... too many issues with this theory.
- Mass migration moved diseases around which killed the dinos. This wouldn't be enough to remove them all, but it's got some good points: it would target large mobile critters more, and a disease would be more likely to affect similar animals (like dinos) but exclude others. Still, there are issues here...
- Deccan Traps. When India slammed into the Asian continent, it pushed up the Himalayas, and created lava flows that covered millions of square acres. The amount of ejecta from the eruptions could have created a nuclear winter on its own (think St. Helens but millions of times worse).
No one really knows what killed off the dinosaurs, but to say that the asteroid did it itself is ridiculous. It's simply not supported. The dinosaurs were dying off for millions of years; The Cretaceous period started with really high species (dinosaur) diversity... by the end, there were pretty much two species left: T-Rex and Triceratops... the duckbills, the other Ceratopsians, etc, were almost extinct already.Most likely it was a combination of many of these things... Diseases start to ravage certain lineages, others can't compete with new types of plants, and slowly die off. The climate changes due to massive volcanic eruptions, and this adds more challenges to various species. After a few million years of this, dinosaurs as a class are hurting: they have little species diversity left, and are unlikely to recover. An asteroid impact puts the final touch on it...
For more reading check the following links:
A Cowen Essay posted on UCMP
Summaries from UCMP
Also, see The Dinosaur Heresies by Robert Bakker... His ideas are interesting and opposite of much of UCMP's thoughts. But he's definitely worth reading; I recommend this to anyone interested in dinos...