I was wondering what changes in earth’s oxygen levels might have been. O2 in the atmosphere wasn’t always there - so how has it changed. Came across an interesting article and they talk about a possible mechanism that keeps atmosphere levels and climate fairly well-balanced over the millions of years.
I’m always amazed at how wonderful the world is, and how so many things are inter-related. And that if something does go out of whack for awhile, it can recover itself too.
https://www.livescience.com/56219-earth-atmospheric-oxygen-levels-declining.html
Excerpt:
One way out of this conundrum is a well-known but relatively untested concept that suggests “that on timescales longer than a few hundred thousand years, atmospheric carbon dioxide and Earth’s temperature are regulated via a ‘silicate weathering thermostat,’” Higgins said.
Basically, increasing atmospheric carbon dioxide levels will boost the rates at which volcanic rocks wear down and their components wash into the seas, which can then go on to trap atmospheric carbon dioxide in ocean minerals. This means that “one can have a change in atmospheric oxygen with no observable change in average carbon dioxide,” Higgins said. “Importantly, this silicate weathering thermostat is one reason why Earth is thought to have remained habitable for billions of years despite changes in solar luminosity.”
I imagine such an event would blast a lot of vaporized sea water and entrained atmosphere into space.
Maybe we lost half the atmosphere into space? That would be very hard on everything that breathed. Only small burrow dwellers used to breathing oxygen depleted air deep in their burrows or critters who nested by burying their eggs would survive. Which, by some strange coincidence, is pretty much a description of the terrestrial Chicxulub survivors.