The big dying most likely caused by the Siberian traps .....talk about fires! Vulcanism at its most intense
Re: Siberian traps
Here’s an episode from the fantastic How The Earth Was Made series on that event. Episodes from the series should be around 50 min. This upload, for some reason, is just 36 min.
How the Earth Was Made - Earths Deadliest Eruption - Documentary:
https://www.youtube.com/watch?v=B177t5xElQg
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Animal Armageddon The Great Dying - Episode 5
https://www.youtube.com/watch?v=IV5UJo6Kr5c
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This last one is a college lecture...
The Mother of Mass Extinctions: How Life on Earth Nearly Ended 250 Million Years Ago
https://www.youtube.com/watch?v=X3p_8UvWq44