251 million years ago, over 90% of all life in the oceans and 70% of all life on land died. This was the worst mass extinction the Earth ever experienced: the end-Permian extinction.
The trouble started in Siberia, where a massive series of eruptions in the Siberian Traps started taking place. Massive may even be an understatement: it’s estimated that up to 4000000 km³ of lava was spewed out of these volcanoes and rifts by the end of the event (Fedorenko et al., 2000). In other words, imagine if the Greenland ice cap were 50% bigger. Now turn all of it to lava.
When you’re done checking the floor for melting spots, start to consider the effects of such an eruption. The atmosphere’s composition suddenly shifted to contain enormous amounts of carbon dioxide, in this case made worse by some of the volcanic area being filled with organic-rich sediments to burn. In total, it’s estimated that up to three trillion tons of carbon were released (Grasby et al., 2011), as well as a range of poisonous gases and toxic elements (mercury!) (Black et al., 2014).
The end result isn’t merely a greenhouse scenario, it’s an oven. Oxygen isotopes tell us that this was a period of intense global warming and extreme ocean temperatures (Romano et al., 2013), and if that weren’t bad enough, the oceans and the rain also became pretty acidic (Beauchamp & Grasby, 2012), as shown in the diagram above. Oh, and also some of the big oceans of the time, the Tethys and Panthalassa oceans, had no oxygen in them anymore (Xie et al., 2007).
Oh yeah, also no more ozone layer, so any organism that enjoyed the conditions was congratulated with radiation.
Things got pretty bad is all I’m saying. Marine ecosystems were already under considerable stress from the mid-Permian, when local extinctions had begun to happen (Beauchamp & Grasby, 2012), as the diagram above demonstrates. The eruption and its effects finally broke the Earth’s ecosystems.
A great read about the Permian extinction, besides my lecture on it, is Douglas Erwin’s book, Extinction: How Life on Earth Nearly Ended 250 Million Years Ago, now out in a new edition.
The end-Permian extinction was a long, protracted event, the severity of which continued well into the Triassic, with environmental upheavals and stressed ecosystems staying the norm for several millions of years (Song et al., 2014). The hallmarks of the Permian extinction – the very hot climate, the lack of oceanic oxygen, the acidifcation – remained unabated (Grasby et al., 2013).
The recovery of the fauna in the Triassic was pretty spotty, with early to mid-Triassic faunas characterised by opportunistic taxa that conquered then faded quickly, as shown in the above diagram for condonts and ammonoids (Bottjer et al., 2008). Some of these did, however, sow the seeds for the long-term recovery of ecosystems, from the ammonoids of the planktonic realm (Stanley, 2009) to the foraminifera of the benthic realm (Song et al., 2011) and even to proper reefs (Brayard et al., 2011).
Beauchamp B & Grasby SE. 2012. Permian lysocline shoaling and ocean acidification along NW Pangea led to carbonate eradication and chert expansion. Palaeo3 350-352, 73-90.
Black BA, Lamarque J-F, Shields CA, Elkins-Tanton LT & Kiehl JT. 2014. Acid rain and ozone depletion from pulsed Siberian Traps magmatism. Geology 42, 67-70.
Bottjer DJ, Clapham ME, Fraiser ML & Powers CM. 2008. Understanding mechanisms for the end-Permian mass extinction and the protracted Early Triassic aftermath and recovery. GSA Today 18, 4-10.
Brayard A, Vennin E, Olivier N, Bylung KG, Jenks J, Stephen DA, Bucher H, Hofmann R, Goudemand N & Escarguel G. 2011. Transient metazoan reefs in the aftermath of the end-Permian mass extinction. Nature Geoscience 4, 693-697.
Fedorenko V, Czamanske G, Zen’ko T, Budahn J & Siems D. 2000. Field and Geochemical Studies of the Melilite-Bearing Arydzhangsky Suite, and an Overall Perspective on the Siberian Alkaline-Ultramafic Flood-Volcanic Rocks. International Geology Review 42, 769-804.
Grasby SE, Sanei H & Beauchamp B. 2011. Catastrophic dispersion of coal fly ash into oceans during the latest Permian extinction. Nature Geoscience 4, 104-107.
Grasby SE, Beauchamp B, Embry A & Sanei H. 2013. Recurrent Early Triassic ocean anoxia. Geology 41, 175-178.
Romano C, Goudemand N, Vennemann TW, Ware D, Schneebeli-Hermann E, Hochuli PA, Brühwiler T, Brinkmann W & Bucher H. 2013. Climatic and biotic upheavals following the end-Permian mass extinction. Nature Geoscience 6, 57-60.
Song H, Wignall PB, Chen Z-Q, Tong J, Bond DPG, Lai X, Zhao X, Jiang H, Yan C, Niu Z, Chen J, Yang H & Wang Y. 2011. Recovery tempo and pattern of marine ecosystems after the end-Permian mass extinction. Geology 39, 739-742.
Song H, Tong J, Algeo TJ, Song H, Qiu H, Zhu Y, Bates S, Lyons TW, Luo G & Kump LR. 2014. Early Triassic seawater sulfate drawdown. Geochemica et Cosmochimica Acta 128, 95-113.
Stanley SM. 2009. Evidence from ammonoids and conodonts for multiple Early Triassic mass extinctions. PNAS 106, 15264-15267.
Xie S, Pancost RD, Huang J, Wignall PB, Yu J, Tang X, Chen L, Huang X & Lai X. 2007. Changes in the global carbon cycle occurred as two episodes during the Permian–Triassic crisis. Geology 35, 1083-1086.