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This is: Pangea: The Worst of Times, published by John G. Halstead on the AI Alignment Forum.
260 million years ago, our planet had an unfamiliar geography. Nearly all of the landmasses were united into a single giant continent known as ‘Pangea’ that stretched from pole to pole. On the other side of the world you would find a vast ocean, even larger than the present Pacific, called Panthalassa. The Pangean era lasted 160 million years, and 80 million of these were extremely inhospitable to animal and plant life, coinciding with two mass extinctions and four other major extinction events. This is why Paul Wignall, a Professor of Palaeoenvironments at Leeds has called the Pangean era ‘The Worst of Times’. Understanding why the Pangean era was so miserable helps inform several questions of interest to those studying existential risk.
● What level of natural existential risk do we face now, and have we faced in the past?
● What is the threat of super-volcanic eruptions?
● How much existential risk does anthropogenic climate change pose?
1. Background
There have been five mass extinctions so far. The Ordovician–Silurian (450-440 million years ago) and the Late Devonian (375-360 million years ago) each preceded the age of Pangea. The Pangean period coincided with the two worst mass extinctions, the huge Permian-Triassic mass extinction (252 million years ago) and the Triassic-Jurassic extinction event (201 million years ago).[1] The last crisis, the Cretaceous–Paleogene event (65 million years ago), accounted for the dinosaurs and occurred once continental drift had done its business and Pangea had broken apart. With the exception of the end Cretaceous extinction, since the breakup of Pangea, it has been relatively plain sailing for Earth’s various species, until humans started killing off other species themselves.
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As one can see on this diagram, in the 145 million years since the start of the Cretaceous, the average rate of global genus extinctions from extinction events has been around 5% and never passed 15%, except for the death of the dinosaurs. But in the 80 million years from the first Pangean extinction event, the Capitanian, to the early Jurassic extinction events, the average rate of global genus extinctions in extinction events is more around 15-20%, and 12 events produced global genus extinction rates in excess of 15%.
Below is a useful chart from Wikipedia on the Phanerozoic, which shows the long-term trend in biodiversity as well as the impact of different extinction events.
Again, this highlights how unusually bad things were in the Pangean era - specifically the 80 million years after the Capitanian extinction event 260 million years ago. But it also highlights how good things have been since the end of the Pangean era and the start of the Cretaceous (145 million years ago).
2. What caused such ecological trauma in Pangea?
Huge volcanic eruptions were implicated in all of the six major extinction events in the Pangean era. One can see this in the first diagram above, where the volcanic eruptions are shown at the top and the line traces down to corresponding extinction events at the bottom. Every Pangean extinction event coincided with the outpouring of enormous fields of lava that, once cooled, produced what geologists call Large Igneous Provinces (LIPs).[3]
To put these LIPs in context, the eruption of Mount Pinatubo in 1991 produced 10 cubic km of magma, which caused the Earth to cool by about half a degree. The eruption of the Siberian Traps which appeared to cause the end Permian extinction produced 3 million cubic km of magma. You can see the volume of magma for all major LIPs at the top of the first diagram above.
These volcanic eruptions emitted sulphur dioxide, carbon dioxide and halogen gases, each of which could potentially have an effect on the ecosys...
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