/sci/ - Science & Math

>>9459540
relationship between temperature and terrestrial & marine extinction levels during the end-Permian

>>9040335
the ultimate cause seems to be the eruption of the Siberian traps, not only because it fits timing-wise, but the expected results are also consistent with geologic evidence.

The main alternative hypothesis was bolide impact, but this is largely rejected because
a) the evidence for it (allegedly extraterrestrial noble gases, a weak iridium anomaly,...) is too uncertain
b) there is a lack of craters of adequate age (251ma)
c) an impact event wouldn't be consistent with the selectivity of the crisis

The generally accepted scenario to date is this:
The Siberian traps erupt and also ignite older coal seams, which injects a huge amount of carbon and sulphuric acid into the atmosphere. The Earth system then responds nonlinearly to this perturbation:
>sulphuric acid gets removed from the atmosphere by wet deposition (i.e. acid rain), which kills most of the terrestrial plants
>as a result, soils become less coherent and get washed into the ocean (there is evidence for massive erosion)
>sudden input of nutrients from soils cause the shelf area to undergo hypertrophy and subsequent anoxia
>CO2 in the atmosphere produce a "super-greenhouse", possibly causing catastrophic outgassing of methane clathrates, amplifying the warming
>there is an "Equatorial Vertebrate Eclipse", where almost all evidence of complex vertebrates (both marine and terrestrial) disappears from low-latitudes
>large quantities of CO2 and sulphuric acid dissolve in the ocean
>pH drops and heavily calcified marine organisms die out
>for a 'short' period of time, all evidence for the existence of forests disappears from the geologic record
>sudden spike in fungal spores
>delta13C shows biggest excursion for the entire Phanerozoic and continues to oscillates violently for millions of years as the carbon cycle is thrown into mayhem, before it suddenly stabilizes in the Middle Triassic

So the Permo-Triassic is correctly described as an "apocalyptic global warming event"