Friday, October 18, 2019

Relationship of Great Extinctions to CO2 Levels

Each major extinction event has been caused by either too little carbon dioxide in the biosphere 
[search: Cyanobacteria + Great Oxygenation Crisis + Snowball Earth] 
too much carbon dioxide 
[search: large igneous provinces LIPs]
Example: even the extinction of the dinosaurs had occurred prior the infamous asteroid strike (search: 3 meter gap + Deccan Traps).

Too Little CO2 —
Cyanobacteria Snowball Earth:
Related reading essential for understanding posting:
[Note: During the first half of Earth’s geologic history, the biosphere was very hot. What kept the temperature up was high levels of methane (a strong greenhouse gas) and carbon dioxide. Cyanobacteria then evolved and began consuming the CO2 and releasing oxygen (which had not existed as a free gas in the biosphere previously). This oxygen combined with the methane to yield  carbon dioxide which the Cyanobacteria consumed — and this process repeated itself on and on until the greenhouse gas levels were so low that not enough thermal radiation could be trapped to keep the planet from freezing solid.]

Too Much CO2 —
LIPs — Large Igneous Provinces:

Extinctions Tied to Carbon Dioxide:

In short, the single biggest driver of mass extinctions appears to be major changes in Earth’s carbon cycle such as large igneous province eruptions, huge widespread volcanic events that flooded hundreds of thousands of square miles for prolonged periods of time with lava. These eruptions ejected massive amounts of heat-trapping gases such as carbon dioxide into the atmosphere, enabling runaway global warming and related effects such as ocean acidification and anoxia, a loss of dissolved oxygen in water.

Large Igneous Provinces / Flood Basalts (16 minutes):