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.

Comments

There's been a lot more than two

[ynotds]

Note that there are two different big extinctions

There are generally five biggies identified since the "Cambrian explosion", the sudden diversification of animal body plans/phyla, these being identified with the Cambrian, Ordovician, Devonian, Permian and Cretaceous geological periods.

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 ... the smoking gun for the late Stephen Jay Gould's theory of punctuated equilibrium.

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.

Heh :)

[CyberDruid]

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.

Rise of the dinosaurs

[ammonoid]

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.