The Great Dying: Disaster occurred and most life on the Earth was wiped out 251 million years ago.
Dublin 20th May 2010
The so called Great Dying event that occurred
251.4 million years ago between the Permian and Triassic geologic periods has been considered the most severe extinction event of all the times. Up to 96 percent of all marine species and 70 percent of terrestrial vertebrates species became extinct. It is the only known mass extinction where insects were extinct (83% of all genera were killed). Most of the diversity on the Earth disappeared. Siberian traps eruptions that triggered releases of carbon dioxide and methane are among the possible causes (knoll et al., 2007). These would have accelerated global warming and severe anoxic events in the oceans, following the action of anaerobic sulfur-reducing organisms (that live without oxygen) that modified the chemistry of the oceans and emit poisonous hydrogen sulfide.
Isotopic analyses of O18 and O16 ratios revealed that during this period a super greenhouse warming of up to 6 degrees took place quite rapidly and the climate went form wet to arid just at the time when nearly all life forms over the Earth vanished.
North Italy rock exposures and other parts of the world tell the tail of catastrophic event where eroded soils were washed by enormous torrents into the ocean. The 12 mm of layer of clay at the Meishan rock beds in the Zhejiang (South China), represents to geologists the most indubitable evidence of what happened 251 ma ago (Uranium chronologically dated). Disaster occurred and most life on the Earth was wiped out. Fossils disappeared from the stratigraphical sequence and gave place to a clayey layer of quartz and volcanic ash underneath dark mudstones rich in organic matter (poor oxygen conditions). See Figure 1.
Antarctica rocks in the central Transantartic Mountains show a huge increase in chemical weathering by acidic rain, caused in turn by extremely high levels of CO2 in the atmosphere together with evidences that this was a quite rapid event (less than 10,000 years).
One of the possible causes is the fact that tectonic building ceased and lack of chemical weathering allowed high atmospheric CO2 levels. Close to the beginning of the Permian these high levels of CO2 (forth times higher than now) gave a boost to temperatures and lead to a series of positive feedbacks.
In hotter poles the sinking of cold water that we see today stopped. Warm seas imply less oxygen can be dissolved on it leading to stagnant anoxic conditions. Of course sea level rise that invaded shallow continental shelves where anoxic process got intensified. Meanwhile this global warmth of the oceans fuelled super hurricanes triggering immense flash floods at the coast and transported heat to higher latitudes, intensifying even more the greenhouse effect by water vapour and clouds formation.
This wasn’t all, super big eruptions over large igneous provinces such as the Siberian Traps (~250 million years ago) were on their way ending on big explosions of basalt and dust and realising billions of tones of CO2 and poisonous gases that materialised into acid rain washing out dead vegetation into the already life-decaying oceans.
Oxygen levels dropped to 15% (currently air concentration is 21%). After global warming accentuated, methane hydrates saturated ocean waters that eventually released through strong explosions of high toxicity similarly to those CO2 releases that occurred in a Camerron’s lake in 1986 with the difference that unlike CO2, methane is flammable. Not much different from vacuum bombs that the US army uses. The air-methane mixture is explosive at methane concentrations between 5% and 15%. Methane air clouds produced by ocean explosions are extremely powerful, capable of propagating at several km per second evaporating any living reptilian vertebrate on their way. As Gregory Rysking stated ‘this could have terminated with all forms of life on the face of Earth’, likely for us it didn’t.
A great methane explosion in the ocean would liberate approximately the equivalent of 108 megatons of TNT, that is 10,000 times bigger than world’s stockpile of nuclear weapons (Ryskin, 2003). This would have cooled the Earth for a while to rapidly boost temperatures after by the CO2 produced by combusted methane and even worst, the uncombusted methane, a much a powerful greenhouse.
Figure 1 This yello
w rock is where magma burned through a coal bed 250 million years ago, releasing CO2 (www.csmonitor.com)
This could have been aided by hydrogen sulphide that accumulated at depths in oceans (caused by vegetation and animal accumulations) killing oxygen-breathing species in the ocean, and above, once released into atmosphere. Its emissions into the atmosphere would have killed anything ‘still’ alive and at the same time destroying the ozone layer that protects us against UV rays.
Looking at this picture it is not surprising then than 95% species in land and on the sea perished. It took 50 million years for life to recover its former state. Only the pig-like lystrosaurus and sparse vegetation survived after.
Even out sighting a 6 degrees increase by the end of the century, it is obvious that the picture now has changed. Continents are differently arranged allowing different current to address energy balance around the world and good circulation among the oceans; there are not ‘great’ eruptions happening; And finally it seems that we are intelligent enough individuals so we can do something to avoid a catastrophe (Lynas, 20007).
In the other hand now more and more species have been pushed to their ecosystems belt limits leaving them very little room for adaptation comparing with the Permian species. Out gassing of CO2 in the past took a few thousands years (10,000) to happen now we are achieving the same rate of change and warming only in a few decades (in a century).
It is now believed that human releases of CO2 are happening faster during any other time since life is on the Earth, at least not during the last 800,000 yrs. According to Eric Wolff director of the EPICA Project (Antarctica British institute), one of the most advanced projects on Palaeoclimate in Polar regions, argues that the fact that CO2 concentration has risen over 30ppm (parts per million) in the last 17 years compared with the rate emission of 30ppm over the last 1,000 years! is all but a good sign. He also states that ‘there is nothing that indicates that the Earth can assimilate all CO2 we are currently emitting since the pre-industrial era’.
Nowadays tons and tons of methane hydrates are stored in our continental shelves waiting for a trigger to let them go.
If the great ocean circulation belts stopped certainly we would have a cooling effect over this area (Western Europe) for a while, but as the circulation ceases warmer waters would penetrate into depths carrying less oxygen (like the black sea). The Mediterranean would be one of the first to go and this could happen without us noticing as human sense of smell cannot detect hydrogen sulphide once over parts per trillions levels ( Kump, L., et al., 2005)).
We have not reached yet the levels of greenhouse gases concentrations occurred during the Paleocene-Eocene Thermal Maximum or cretaceous. Nevertheless the rate of increase is now unprecedented in the History of our Planet.
Silvia Caloca
References
Knoll, A.H., Bambach, R.K., Payne, J.L., Pruss, S., and Fischer, W.W. (2007). "Paleophysiology and end-Permian mass extinction". Earth and Planetary Science Letters 256: 295–313. doi:10.1016/j.epsl.2007.02.018. Retrieved 2008-07-04.
Kump, L., et al., 2005. Massive release of hydrogen sulfide to the surface ocean and atmosphere during intervals of anoxia. Geology, 33, 5,397-400.
Lynas, M. 2007. "Six Degrees: Our Future on a Hotter Planet". Fourth Estate March 2007 ISBN 000720904.
Ryskin G., 2003 Methane-driven oceanic eruptions and mass extinctions. Geology; September 2003; v. 31; no. 9; p. 741–744.
http://news.bbc.co.uk/2/hi/science/nature/5314592.stm
Dublin 20th May 2010
The so called Great Dying event that occurred
251.4 million years ago between the Permian and Triassic geologic periods has been considered the most severe extinction event of all the times. Up to 96 percent of all marine species and 70 percent of terrestrial vertebrates species became extinct. It is the only known mass extinction where insects were extinct (83% of all genera were killed). Most of the diversity on the Earth disappeared. Siberian traps eruptions that triggered releases of carbon dioxide and methane are among the possible causes (knoll et al., 2007). These would have accelerated global warming and severe anoxic events in the oceans, following the action of anaerobic sulfur-reducing organisms (that live without oxygen) that modified the chemistry of the oceans and emit poisonous hydrogen sulfide.Isotopic analyses of O18 and O16 ratios revealed that during this period a super greenhouse warming of up to 6 degrees took place quite rapidly and the climate went form wet to arid just at the time when nearly all life forms over the Earth vanished.
North Italy rock exposures and other parts of the world tell the tail of catastrophic event where eroded soils were washed by enormous torrents into the ocean. The 12 mm of layer of clay at the Meishan rock beds in the Zhejiang (South China), represents to geologists the most indubitable evidence of what happened 251 ma ago (Uranium chronologically dated). Disaster occurred and most life on the Earth was wiped out. Fossils disappeared from the stratigraphical sequence and gave place to a clayey layer of quartz and volcanic ash underneath dark mudstones rich in organic matter (poor oxygen conditions). See Figure 1.
Antarctica rocks in the central Transantartic Mountains show a huge increase in chemical weathering by acidic rain, caused in turn by extremely high levels of CO2 in the atmosphere together with evidences that this was a quite rapid event (less than 10,000 years).
One of the possible causes is the fact that tectonic building ceased and lack of chemical weathering allowed high atmospheric CO2 levels. Close to the beginning of the Permian these high levels of CO2 (forth times higher than now) gave a boost to temperatures and lead to a series of positive feedbacks.
In hotter poles the sinking of cold water that we see today stopped. Warm seas imply less oxygen can be dissolved on it leading to stagnant anoxic conditions. Of course sea level rise that invaded shallow continental shelves where anoxic process got intensified. Meanwhile this global warmth of the oceans fuelled super hurricanes triggering immense flash floods at the coast and transported heat to higher latitudes, intensifying even more the greenhouse effect by water vapour and clouds formation.
This wasn’t all, super big eruptions over large igneous provinces such as the Siberian Traps (~250 million years ago) were on their way ending on big explosions of basalt and dust and realising billions of tones of CO2 and poisonous gases that materialised into acid rain washing out dead vegetation into the already life-decaying oceans.
Oxygen levels dropped to 15% (currently air concentration is 21%). After global warming accentuated, methane hydrates saturated ocean waters that eventually released through strong explosions of high toxicity similarly to those CO2 releases that occurred in a Camerron’s lake in 1986 with the difference that unlike CO2, methane is flammable. Not much different from vacuum bombs that the US army uses. The air-methane mixture is explosive at methane concentrations between 5% and 15%. Methane air clouds produced by ocean explosions are extremely powerful, capable of propagating at several km per second evaporating any living reptilian vertebrate on their way. As Gregory Rysking stated ‘this could have terminated with all forms of life on the face of Earth’, likely for us it didn’t.
A great methane explosion in the ocean would liberate approximately the equivalent of 108 megatons of TNT, that is 10,000 times bigger than world’s stockpile of nuclear weapons (Ryskin, 2003). This would have cooled the Earth for a while to rapidly boost temperatures after by the CO2 produced by combusted methane and even worst, the uncombusted methane, a much a powerful greenhouse.
Figure 1 This yello
w rock is where magma burned through a coal bed 250 million years ago, releasing CO2 (www.csmonitor.com)This could have been aided by hydrogen sulphide that accumulated at depths in oceans (caused by vegetation and animal accumulations) killing oxygen-breathing species in the ocean, and above, once released into atmosphere. Its emissions into the atmosphere would have killed anything ‘still’ alive and at the same time destroying the ozone layer that protects us against UV rays.
Looking at this picture it is not surprising then than 95% species in land and on the sea perished. It took 50 million years for life to recover its former state. Only the pig-like lystrosaurus and sparse vegetation survived after.
Even out sighting a 6 degrees increase by the end of the century, it is obvious that the picture now has changed. Continents are differently arranged allowing different current to address energy balance around the world and good circulation among the oceans; there are not ‘great’ eruptions happening; And finally it seems that we are intelligent enough individuals so we can do something to avoid a catastrophe (Lynas, 20007).
In the other hand now more and more species have been pushed to their ecosystems belt limits leaving them very little room for adaptation comparing with the Permian species. Out gassing of CO2 in the past took a few thousands years (10,000) to happen now we are achieving the same rate of change and warming only in a few decades (in a century).
It is now believed that human releases of CO2 are happening faster during any other time since life is on the Earth, at least not during the last 800,000 yrs. According to Eric Wolff director of the EPICA Project (Antarctica British institute), one of the most advanced projects on Palaeoclimate in Polar regions, argues that the fact that CO2 concentration has risen over 30ppm (parts per million) in the last 17 years compared with the rate emission of 30ppm over the last 1,000 years! is all but a good sign. He also states that ‘there is nothing that indicates that the Earth can assimilate all CO2 we are currently emitting since the pre-industrial era’.
Nowadays tons and tons of methane hydrates are stored in our continental shelves waiting for a trigger to let them go.
If the great ocean circulation belts stopped certainly we would have a cooling effect over this area (Western Europe) for a while, but as the circulation ceases warmer waters would penetrate into depths carrying less oxygen (like the black sea). The Mediterranean would be one of the first to go and this could happen without us noticing as human sense of smell cannot detect hydrogen sulphide once over parts per trillions levels ( Kump, L., et al., 2005)).
We have not reached yet the levels of greenhouse gases concentrations occurred during the Paleocene-Eocene Thermal Maximum or cretaceous. Nevertheless the rate of increase is now unprecedented in the History of our Planet.
Silvia Caloca
References
Knoll, A.H., Bambach, R.K., Payne, J.L., Pruss, S., and Fischer, W.W. (2007). "Paleophysiology and end-Permian mass extinction". Earth and Planetary Science Letters 256: 295–313. doi:10.1016/j.epsl.2007.02.018. Retrieved 2008-07-04.
Kump, L., et al., 2005. Massive release of hydrogen sulfide to the surface ocean and atmosphere during intervals of anoxia. Geology, 33, 5,397-400.
Lynas, M. 2007. "Six Degrees: Our Future on a Hotter Planet". Fourth Estate March 2007 ISBN 000720904.
Ryskin G., 2003 Methane-driven oceanic eruptions and mass extinctions. Geology; September 2003; v. 31; no. 9; p. 741–744.
http://news.bbc.co.uk/2/hi/science/nature/5314592.stm
Further information
Benton M J (2005). When Life Nearly Died: The Greatest Mass Extinction of All Time. Thames & Hudson. ISBN 978-0500285732.
Bowring SA, Erwin DH, Jin YG, Martin MW, Davidek K, Wang W (1998). "U/Pb Zircon Geochronology and Tempo of the End-Permian Mass Extinction". Science 280 (1039): 1039–1045. doi:10.1126/science.280.5366.1039.
Jin YG, Wang Y, Wang W, Shang QH, Cao CQ, Erwin DH (2000). "Pattern of Marine Mass Extinction Near the Permian–Triassic Boundary in South China". Science 289 (5478): 432 436. doi:10.1126/science.289.5478.432. PMID 10903200.
Knoll, A.H., Bambach, R.K., Payne, J.L., Pruss, S., and Fischer, W.W. (2007). "Paleophysiology and end-Permian mass extinction". Earth and Planetary Science Letters256: 295–313. doi:10.1016/j.epsl.2007.02.018. Retrieved 2008-07-04.
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