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Lava Flow May Have Caused Extinction
Pinhead writes "From MSNBC, it appears a new study suggests that a massive extinction that occurred 250 million years ago may not have been an asteroid but a large lava flow that spewed large amounts of poisonous gases in the air. This extinction led to the rise of the dinosaurs." Note that there are two different big extinctions: this first one occurred when plant life was mostly ferns, and all the continents were together in Pangaea. The later one is the one that everyone knows about, that wiped out the dinosaurs.
Thar's oll in them thar hills!
I have been pwned because my
There's some genetic evidence that humans were reduced in number from 100,000 to 10,000 about 75,000 years ago. Some think that it was because of a major eruption in Indonesia.
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If tits were wings it'd be flying around.
Note that there are two different big extinctions
There's been a lot more than just two mass extinctions over the history of the earth - there's evidence of events where up to 90% of existing species have disappeared scattered throughout the fossil record. Some of these have probably been caused by meteorite or comet impacts, others quite possibly by large geological events - massive lava outpourings can release enough CO2 into the atmoshpere to have a definite effect on world climate.
However it doesn't take a lot of imagination to realise that the abrupt changes in the rocks which have long guided geologists to divide geologic time into distinct epochs must be due to global changes in the ecology, especially in marine microorganisms
This overview of the big five events and their causes shows them bracketed by a pair that led into the Cambrian explosion and a seemingly human induced one.
There is a lot of conjecture about causes for specific extinction events, IMNSHO mainly due to the growing human (and especially scientific) demand that causes be singular. Purported causes include extensive glaciation which is relatively easy to spot in the geological record, flood volcanism, which is a bit harder because it is relatively localised, and impacts, the most recent of which at least managed to leave a layer enriched with iridium and a large crater.
But even re that most recent dinosaur ending event there is still evidence that the Deccan Traps lava flood may have played a role, as there are persistent claims for impacts as well as Siberian lava flows around the time of the real biggie at the end of the Permian which this article focuses on.
Personally I'm leaning more and more towards a double whammy theory of mass extinction that would require some sustained global stress complemented by a more sudden knockout punch. And that doesn't get humanity off the hook.
Of more consequence for populist misinterpretations of Darwin's great insights is that it has needed the slate to be wiped almost clean many times before an opportunity arose for mammals, let alone humans, to rise to prominence.
As co-conspirators in the rise of imformation technology we should be able to see the importance of mass extinctions opening opportunities for those who may be better at innovation.
-- Our systemic servants do not good masters make.
I am actually having an exam on this subject in 30 mins. Guess I'll come loaded with _the latest_ developments...
Seriously though - that the 250 m.y.a. extinction was not caused by a asteroid, but by volcanic activity in Siberia, has been the general opinion for quite some time.
Opinions stated are mine and do not reflect those of the Illuminati
Cockney old sod did contract penis tumors juggling cold testicals quickly
A nice easy rhyme to remember
Cambrian - Ordivician - Silurian - Devonian - Carbiniferous - Permian - Triassic - Jurassic - Cretaceous - Tertiary - Quaternary
The dinousaur one was at the K-T Boundry (Cretaceous - Tertiary), end of the mesozoic IIRC.
The other big one (trilobites and about 90% of the earth - I think, its been a few years) was this one, and at the start of the mesozoic (Permian - Triassic)
Well we know M$ is bad, but MSNBC extincting an entire species with a lava flow?
Make even shorter URLs - 8LN.org
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The attempt by the BBC to link the rise of the dinosaurs to the Permo-Triassic extinction is a mistake. Both synapsids (mammalian lineage) and diapsids (dinosaur lineage) coexisted during most of the Triassic. Then at around 210 M.y. there was a sudden shift in the diversities of the two groups, which allowed the dinosaurs to dominate the terrestrial ecosystems until the end of the Cretaceous. This does not seem to be related to competitive interactions between the two groups, and may have been driven by an extinction event towards the end of the Carnian (a Triassic subdivision). The full reference is: Benton, M. J. 1983b. Dinosaur success in the Triassic: a noncompetitive ecological model. Quarterly Review of Biology, 58, 29-55.
"Hope is a duty from which paleontologists are exempt." David Quammen
nature.com has this story about it too. Seems fairly closely matched with the displayed link.
The return of catastrophism to geology was marked by the widespread acceptance of the bolide impact at the K-T boundary. An excellent book on this subject is "Mass extinction debates: How science works in a crisis" William Glen (ed.). Most geologists accept that there are events in the geological past that have no present analog. As to your rather narrow vision of "the scientific method", this falsificationalist view is that of the earlier works of Karl Popper. Historical science is inferential, and tries to assign probabilities to what happened, just as human histories do. As for what experiments can tell you, the Miller-Urey experiment told us something about how the possibility of complex organic molecules emerging. That is an experiment that tells us something about what might have been going on 4 B.a. As to the rates of eruption quoted in the article, there is abundant radiometric dating evidence from the Siberian Trappes. The rate of eruption is then simply the change in rock area or volume over the calculated time. The links to the mass extinction may be more tenuous, but there is no question that a major change in the marine organisms occurred aroudn the Permo-Triassic boundary.
"Hope is a duty from which paleontologists are exempt." David Quammen
The Chicxulub crater in Mexico is very nearly opposite the Deccan traps, which have both been fingered for the extinction of the dinosaurs 65 million years ago. There is also a possible large impact site in Australia of the right age, which would have been almost exactly opposite the Siberian Traps at the time of the Permian extinction 250 million years ago. On the planet Mercury there is a gigantic impact crater called the Caloris basin, which is also directly opposite "weird terrain" caused by focussed shockwaves.
Summarised from Terry Pratchett et al, "The Science of Discworld", pp 307-308, discussing mass extinctions, and the surprisingly essential role they appear to have played in the evolutionary history.
By 1900 textbooks were claiming the Earth was 2GYa. Decades before radiometric dating. Yes Hutton, Lyell, etc. were in the millions not billions of years, but those following them extended it.
By the 1960s we were taught the Earth was 3.5 GYa, and now it's 4.5-4.6 as "conventional" wisdom.
BTW trees put on rings based on seasons, and many cases are recorded of multiple rings per annum.
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Wouldn't a massive asteroid, say the likes of the one that cuased the creation of the Yucatan peninsula and the deepening of the Gulf of Mexico (discovered by no other than the Shoemaker-Levy dynamic duo based on satellite photos), cause some MAJOR seismic/techtonic/volcanic activity?
If someone punches you in the stomach while you are swallowing some milk, it's gonna shoot out of your mouth, nostrils, and possibly your ears.
Same thing with Earth. Punch it in the Yucatan and shit is gonna spray everywhere. Lava, dust, critters...everything.