# Would This Mesozoic Great Dying Still Be Just As "Great"?



## Jdailey1991 (Nov 22, 2016)

252 million years ago, Earth underwent its worst, most violent chapter in the form of the Permian-Triassic extinction event, or "The Great Dying". 70% of the terrestrial species and 95% of the marine species became extinct.

In the Earth Science Stack Exchange, I had asked why the Permian-Triassic Extinction event was known vernacularly as "The Great Dying", or why it took Earth ten million years to regain its complex, permanent ecosystems. The answers I got were that the Siberian flood basalt eruptions, though pretty dramatic, weren't the sole culprit. Ocean anoxism as a result of Panthalassa's relationship to Pangaea seemed also to play a part in delaying the re-oxygenation process:



> Its complex structure is driven by the location of the continents. Without continents spread around the world, the ocean circulation would look more like the Pacific ocean, with three separate gyres (probably four if Antarctica was not there, as in the Permian) and much smaller areas of upwelling water:
> 
> Reduced complexity of ocean circulation could reduce the ability of the ocean recover oxygen levels. Deep water anoxia especially would take far longer to correct with reduced upwelling currents.



To put this into perspective, here is planet Earth before 252 million years ago:








n an alternate Earth, a repeat of the Siberian eruptions plagued the Earth during the Maastrichtian epoch, 66 million years ago. Here is Earth at that time:







Note that at this time, the arrangement between continents and oceans were more flexible at the end of the Cretaceous than at the end of the Permian.

In this alternate scenario, instead of lava oozing off India or a comet slamming into Mexico, it is flood basalt eruptions covering an area of seven million square miles of Siberia (and maybe bits of Mongolia and China, as well) and a volume of one to four million cubic miles. Taking the quote above into consideration, would a Mesozoic-Cenozoic "Great Dying" still destroy 70% of all terrestrial and 95% of all marine species, and would biotic recovery still take ten million years?


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## Jackarandajam (Nov 22, 2016)

For someone who isn't versed in theoretical evolutionary history, your terminology, specifically your period references, are a bit... esoteric. Specific to your field of study, I mean. If you're asking if the two maps would have similar geological implications, the answer would be, in my opinion, no. IF you're worried about a few million years. If you're asking why a second "great dying" isn't known as THE "great dying," my question would be: what percentage of life died at the 66 million years ago mark? Because if it was only 60%, it's still justifiable to call the largest "the great dying."

Maybe specify your question with pertinent information? 
Or just clarify; I'm a lowly fiction writer, not a scientist. Although I'd love to help answer your question in any way I can, I might require more explanation than you're used to giving.


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## Chessie (Nov 22, 2016)

I'm assuming...yes...because the terrestrial animals would drown (basalt eruptions only occur underwater I believe). Far as the marine life goes, depending on rising waters there would, I assume, be landslides that fall into the ocean thus destroying the marine life. The "yes" pertaining to a mass extinction; although the 75% might not be the actual number consider the circumstances would be different so who's to say what the percentage would be according to your hypothesis. However, you also might want to look into some mass extinctions that took place in the American midwest and Colorado River die offs from rising ocean levels. 

Would it take 10 mill for the Earth to recover? Who knows. Once again, that would depend on the percentage above and its shift. So, answering your question scientifically might require a professional discussion with a Historical Geologist. That would be fun. But off the top of my head, the answer is "it depends".  May I ask why you're asking? Is it for a fantasy world? Are there further details you could share?

EDIT: On second thought, it might not take millions of years for life to re-establish on the planet if the cause for extinction were salt basalt. There were many periods of mass extinctions throughout Geological history that saw a resurgence of life in thousands of years vs millions. Your biggest questions would have to do with water temperature, water levels, and atmosphere. How would they be affected by this type of natural disaster? How much land would still be available for terrestrial animals? Would the oceans be able to support life and feed the world, basically? So the condition of the land after such an extinction would be the largest dilemma.

EDIT#2: Actually...I might be wrong about the basalt. I know that pillow basalts form underwater, but after a Google search it appears that basalt can also form out of water. Excuse me it's been 10 years since I was last in a Geology class so my memory is a bit shabby. So this changes things. If the salt basalt forms on the surface, then it seems likely that the result would be close to the same as with the lava, especially given the fact that basalt cools into solid state over time. That would surely kill land and marine life. Would it take 10 mill years to have life back? Once again, that depends. Is lava more destructive than basalt? Idk.


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## Jdailey1991 (Nov 23, 2016)

Chesterama said:


> May I ask why you're asking? Is it for a fantasy world? Are there further details you could share?



It's for an alternate history textbook.


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## Chessie (Nov 23, 2016)

What a fascinating idea! I wish you good luck with it then and hope you're able to get more scientifically accurate answers to your questions.


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## Tet (Dec 2, 2016)

Cool Idea, I like stuff about evolution and ancient history. Best of luck to ya good sir.


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