What sort of natural phenomenons could occur that would affect the entire world?

Meteors, asteroids, black holes, YAY! ♥

A huge volcanic eruption, like what happened at Krakatoa. Clouds from that eruption changed the weather throughout the world, and distorted the color of the sky.

@MRSHINYSHOES wow, just did a bit of reading about the history of that volcano… amazing that the earth could do something so powerful.. 13,000 times the nuclear yield as the bomb that wiped out Hiroshima??!!! Wow. Just wow.

Death from the Skies

@the100thmonkey YAY! I ♥ death from the skies! Scientific and space events render me as helpless as a turkey in the rain. If anything of the sort approached me I would happily stand there and get consumed and my human instinct to run would never even tick to kick in. LOL

It dawned on me just today that we are all here with a life sentence with no possibility for parole. It was a tremendously liberating realization that I can do the time. I’m closing in on 70, and I now know I can serve out my sentence and even enjoy it. That said, you can cut your time short by opting for early execution. Of course, there is the do-it-yourself form, and the ever popular do it by idiocy form so popularized by videos like Jackass. But the early death sentence can come from on high, as well.

The Warden may decide that it’s time for another super-volcano such as @MRSHINYSHOES & @digitalimpression allude to. Santorini is one of the world’s super-volcanoes, and its caldera is still active. But did you North American Jellies know that Yellowstone Park houses the largest volcanic caldera on the planet? It is active and showing signs of increased activity. The caldera floor is swelling upwards. It is overdue for a super eruption. When (not if) that comes, it will produce a nuclear winter of far greater magnitude than the Santorini eruption Many plant and animal species will go extinct. Billions of humans will freeze or starve. But humanity will probably adapt and go on.

An asteroid hit like the one that wiped out the dinosaurs 65 million years ago would be more problematic. Something like ⅔rds of all species on earth perished in that cataclysmic event. An asteroid roughly the size and mass of Mount Everest, and traveling at around 40,000 MPH plunged into the Yucatan Peninsula at Chicxulub. creating firestorms over much of the earth’s surface The energy release was roughly 2 million times greater than the 50 megaton Tsar bomb, the largest nuclear device ever exploded by man. The dust cloud that created so thoroughly blocked the sun that many a species simply froze to death.

And then there is the Gamma Ray Burst. A GRB is the most powerful force known in the existing Universe. Only the Big Bang released more energy. Fortunately, the energy releases are highly columinated, so they do their damage in a tightly confined straight line. But anything within thousands of light years of ground zero is absolute toast.

My opinion ta this situatione is.The possible chances are asteroids,meltdown,the earth will rip self a part form the tectonic plates or it is gona be ok for cup of hundred years.Mean to say our generatione will pass this questione

Polar shift
:)
TBH, If you can even comprehend 1/1000000th of the size of the universe you will accept that we are but a meaningless speck in an ever expanding & chaotic universe and anything can happen.

Every great now and then, Earth’s magnetic field flips so that “north” becomes “south” (this is a different phenomenon from the polar shift mentioned by @Boogabooga1 ). The last reversal happened about 750,000 years ago, which is a fairly long period of stability, as these things go.

The main worry is that the magnetic field is responsible for shielding us from all kinds of nasty solar radiation. When these shifts happen, they are preceded by a centuries-long period of chaotic jumping around of the field, with temporary poles appearing here and there, and huge gaps opening up in the field. This would expose us and our infrastructure to full doses of solar yuck.

Moving the Moon would affect the whole Earth. Move it in, and tides become more extreme. Move it out, and water stagnates, and stuff dies.

@ETpro Wow. I had no idea that some of those things even existed.. I suppose the answers have died out enough for me to say that I am collaborating on a project/story involving the demise of mankind. We really struggled to come up with a feasible, plausible, explanation for the biological/whatever damage that would wipe out the entire species whilst leaving animals alive and the environment survivable.

@pathfinder sort of a meltdown of the earth’s core? hmm, I wonder what the effects would be of that actually happening

@thorninmud We acutally considered this idea but not knowing enough about magnetic fields we ruled it out as a possible culprit. Perhaps it warrants more in depth investigation.

@Nullo Would the tides be the only affect? Or does the moon do anything else for the earth? I am very ignorant when it comes to the cosmos. =)

@digitalimpression
Reducing the strength of the tides would reduce the amount of drag that the seas have on Earth’s rotation. This drag (and I think that Sol exerts some, too) will, over time, slow and eventually stop rotation, leaving one side to bake and the other to freeze. The land along the terminator might still be habitable, but would be subjected to high winds – provided that the atmosphere sticks around through the millennia.
It also absorbs – or absorbed – or might absorb – a lot of meteoric activity that might otherwise hit Earth, but I don’t see that being altered such a small change in distance.
Lunar calendars would be screwed up.
The Lagrangian points would all move. That doesn’t matter yet, but any kind of future in space would probably use them for something.

@Nullo Lagrangian points? o.O (web search imminent)
How do you know this stuff? xD

@digitalimpression I read a lot, and have excellent trivia retention. Wikipedia has plenty to read about space, and Schlock Mercenary can be rather educational.

@digitalimpression Thanks for the context. You need a saga of a story to tell, then. Suppose a epedimic breaks out with a pathogen such as emola. Even buring the genetic material that causes it does nothing to mitigate its killing power. The WHO surrounds the area, and they shoot anyone who approaches the perimeter. Just as it appears man has contained it, another asteroid of a size similar to the Chicxulub asteroid strike occurs at ground zero for the ebola outbreak. The pathogens are transported into a stratospheric dust cloud from which they slowly settle over the entire face of the earth. One by one, all of mankind dies off.

Oh, and Happy Jewish New Year.

@ETpro Well, aren’t you the ray of sunshine.

@Nullo I don’t care what people say about Wickipedia… I love it and I always will as long as there other references, I’m good! I have learned so much from that website!

A Tunguska-like event over water near a populated coast, or over a metropolitan area would be devastating. It may not wipe the world out, but it would put a smack down on the Earth that mankind would experienced for much of a decade.

@Nullo Absoltely. Anything I can do to brighten up the day for a friend, consider it too much mork for me to bother. :-)

@ETpro Our current idea is actually a combination of some of the things you said. Our challenge is that this biological event has to turn everyone into zombies somehow. Making zombies believable is actually challenging. lol

@digitalimpression You;ll have to turn to something like Wikipedia to research Zombie biology. That’s one topic where I am admittedly ignorant.

The La Palma megatsunami would kick the whole world’s arse. We’re not talking megadeath, but for the US to lose its primary economic hub could have dire, dire consequences for world stability.