"Extinction events" Topic

Without nuclear war, earth has experienced 5 catastrophic mass extinctions. Theories abound regarding these ancient events, including ET. impacts, volcanism, oxygen depletion, and climate shifts. All of these events occurred long before the rise of industrial civilization according to conventional geology. There have been around 15 ancient impact craters identified around the planet, with the Cretaceous-Tertiary crater being the largest. The current eruption on Iceland, the 2011, magnitude 10 quakes happening now and then. Brings to my mind a line from Crane's story "The Open Boat. It goes something like, "The lighthouse stood like a giant. Turning its back to the pligh of the ants."

Freeze, Freeze, Bake, Bake, Boom!

That is, Earth has twice experienced a Global Snowball mass extinction, twice experienced massive run-away global warming, and then BOOM is the Chicxulub impact. The most recent "Holocene Extinction Event" is , largely driven by current Green Politics and theoretical models that don't hold water when examined.

Interesting theory about these mass extinctions also being tied to the Solar Orbit around the Galactic Center. The Solar System's orbit is not planar, but more of a corkscrew that spirals along going both above and below the Galactic Ecliptic. When it does so the Solar System is exposed to a significant increase in cosmic radiation, which is linked to cloud formation and global cooling. If at the same time the Solar System passes through a large Dust Cloud then the Sun's heliosphere is compressed leaving Earth even more vulnerable to high levels of cosmic radiation. Right now we're in what's called a "local bubble" of low gas/dust density, but if the Solar System passed through a nebula or dense dust cloud, the night sky would appear to be devoid of all stars except the Sun, and the Earth would enter a serious global cooling/potential mass extinction event.

Supervolcanoes: Yellowstone Caldera. If it goes, so do we. The End.

Pandemic of something much, much, much worse than Covid. We actually got very lucky on that one, with a disease that wound up at less than 1% fatality rate (which is not to diminish those deaths or the grief). The fortunate thing is that most truly lethal viruses, as Ebola, have a very limited spread range because they kill off the hosts so quickly. Less lethal viruses survive longer to spread, and eventually evolve into milder forms, as a dead host is a dead end.

Magnetic pole reversal: Yep, it's a thing. And it doesn't sound all that drastic until you realize that when it happens the Earth's magnetosphere, which protects us from solar and cosmic gamma radiation, goes pfffft. (It comes
back, but life will be fried in the meantime.)

Gamma Ray Burst: Highly unlikely, but if one of these things were to happen "close" by, we'd be in biiiiiiggg trouble. (Actually, pretty much all life as we know it would end.)

POPULATION COLLAPSE:
No kidding. It is entirely possible for a species to "die out" from the simple effect of not having enough offspring to sustain population replacement. Probably self-correcting, but the "winners" of that fight will be the ones who lean towards maximizing pregnancy rather than eliminating it. Traditionalist groups will therefore be in good stead. Sexual "progressives" will discover they are an evolutionary dead end.

TOTALLY "OUT THERE" EXOTIC EXTINCTION EVENTS:
Rogue black hole travels close to solar system. That would really suck.

Alien FTL "Braking" "Oops": Possibly impossible anyway, but one of the drawbacks of currently viable warp theory is that a spaceship coming out of a space-time warp would produce a gamma ray shock wave extending from its bow (similar in effect to a GRB). Such a wave would pretty much sterilize anything in its path. And that would include us. So aliens, if you do come for a visit, please do the hard stop beyond us, then reverse at sublight to check us out. (Let's hope they're all just "exploration" minded, because if even one advanced alien civ is bent on conquest and extermination, we're done for. It's just too easy to wipe us out from space.)

But right now, I suspect the next extinction level event will be caused by us, and will be based on racial and ideological hatred coupled with the political idiocy, ignorance and so-called "activism." And it won't be the climate, except as a secondary effect of the nukes flying around.

Good reasons to get a breeding pool off the mudball, and quickly.

If you've got a better plan, Mad Anthony, I'm interested.

And SF has been a comfort and guide to me all my life--which is a lot more than I can say for our political and economic institutions, and far, far more than I can say for our news media or educational system.

'Without nuclear war, earth has experienced 5 catastrophic mass extinctions."

With nuclear war, earth has experienced 5 catastrophic mass extinctions. Unless I missed something.

Not following you, Tgerritsen? Did I miss the nuclear war?

As for flipping magnetic poles, the poles don't flip, the earth does (or might): YouTube link

pzivh43 – I think he means that if there had been a nuclear war, there would have been 6 events. So the OP's clarification "Without nuclear war" could have been left out of the first sentence.

Technically, we've had a nuclear war. It just consisted of 2 bombs and no response.

Just a little one…

Earth enjoys a good reboot from time to time.

You want an extinction event?
Tell a 3 year old who left her wubbie at home that we're not going back to get it!😵

That is what I meant by my first line. Sorry for the confusion.