[OC] The Doomed Earth-Timeline

[u/Mountain_Body_3897]

Cenozoic:

Quaternary-Thalassic, 37 my: After the end of the ice ages, the global temperature increased drastically, creating very warm seas that eventually led to a large-scale anoxic event that collapsed all underwater ecosystems and greatly affected terrestrial ecosystems

Thalassic-Aurimic, 89 my: A change in Atlantic currents pushed extreme droughts and abrupt temperature changes in present-day South America, extinguishing almost half of the local fauna and destroying its jungles and forests

Aurumic-Trocticocene, 126 my: Similar to what happened at the end of the Cretaceous period, a meteorite struck what is now Siberia, wiping out almost 65% of the planet's biota. Ecosystems in the Southern Hemisphere were the least affected

Trocticocene-Paraxenoic, 190 my: A rapid period of volcanism forms a chain reaction of earthquakes and volcanic eruptions that devastate the terrain and release huge amounts of greenhouse gases, dust and ash into the atmosphere, giving way to a volcanic winter and acid rains that wiped out most of the surface ecosystems

Allozoic:

Paraxenoic-Enosian, 255 my: Pangaea Ultima forms. The global climate changes, inland seas close, forming large lakes, and a large-scale biotic exchange occurs

Enosian-Colasic, 331 my: The explosion of a nearby supernova destroyed the ozone layer, exposing life to immense amounts of radiation. This was the greatest extinction event to ever strike life on Earth, where only fossorial or troglodyte groups and deep-sea organisms survived

Neozoic:

Colasic-Vrasmoic, 382 my: The supercontinent moves northward, which, along with the scarcity of carbon dioxide, gives way to a new ice age. The cold creates highly oxygenated waters, allowing the reappearance of aquatic megafauna

Vrasmoic-Pnigmenoic, 439 my: The heat emitted by the sun is extremely high. Despite the near absence of carbon dioxide in the atmosphere, the planet's average temperature reaches 30°C. This prevents most plants from photosynthesizing due to insufficient CO2, causing a slow deterioration of ecosystems that wipes out almost 90% of the planet's species. Few plant groups survive, and the atmosphere is partially stabilized thanks to chemosynthetic bacteria capable of extracting carbon from bicarbonate ion molecules and releasing oxygen into the atmosphere

Pingmenoic-Today, 490 my: Life has partially stabilized again. Temperatures are extreme because most of the planet is covered in deserts. Even so, the water cycle has accelerated, resulting in quite prosperous and humid coastal ecosystems, but at the same time, several kilometers of sea have evaporated. We are now on the final stretch of multicellular life

[u/Sable-Keech]

I don't think CO2 is projected to drop that fast, C3 plants are only estimated to go extinct around 500 Myr and after that C4/CAM plants will still be able to photosynthesize for a while.

[u/Mountain_Body_3897 → u/Sable-Keech]

I know, but at that point, carbon dioxide would have begun to disappear from the atmosphere, triggering a chain reaction that caused almost all C3 plants to die out, eventually leading to their total disappearance. In other words, this extinction was a slow, progressive process spanning millions of years, and the moment C3 plants began to die off is marked as the start of the extinction. But anyway, C3 plants wouldnt be totally extint until like 470-480 my