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Comment by mastax | Hacker News Reader

Looking at that map, it's wild how many "confirmed impact structures more than 100km wide" there are just in Australia. There must be dozens of mass extinction events that we don't know about because the fossil record is so unclear past 500Mya.

[0]: https://en.wikipedia.org/wiki/Extinction_event

[1]: https://en.wikipedia.org/wiki/Chicxulub_crater

[2]: https://en.wikipedia.org/wiki/Earth#Natural_history

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I think this map can mislead you to think that but if you look at the graphs from the reference they quote, there's not much in the last billion years or so that's close to Chicxulub, a known extinction-causing impact. It's a real outlier and it's reasonable to assume much smaller impacts did not cause mass extinctions by themselves. I've fished graphs out here and marked Chicxulub in the first one:

https://i.imgur.com/Rwk6W3j.png

https://i.imgur.com/ATZIK2r.png

That's fun to think about, but Precambrian life was generally microscopic. Many impact craters across the world date from that era, so any extinctions they caused would not be visible to the naked eye.

Maybe they would though?

Individual bacteria aren’t usually visible to the naked eye, but they tend not to exists isolation.

So maybe the immediate post impact world had less pond scum?

During a cave tour one time the guide told us that the darker strata in the marble(?) in the cave walls was from microscopic life in an ancient seabed, and the lighter ones were from periods of...not sure if extinction is the right word, but "less of it".

Google "Chicxulub crater" for a fun animation

For the lazy: https://www.google.com/search?q=Chicxulub+crater

I wonder if more recent events will ever get this treatment?

Maybe in another 60 million years, by whatever the cockroaches evolve into.

Also imagine how many hit the oceans. A water hit can be even more catastrophic than a land hit, especially on shallow water like the continental shelf.

Every 26k years we pass through an asteroid belt with a high probability of impact

26,000 years sounds more like the period for Earth's axial precession. https://en.wikipedia.org/wiki/Axial_precession .

What you describe doesn't make sense. The Earth's orbit is effectively constant at that timescale, as are the asteroids in the main asteroid belt - otherwise interactions with Earth's would have changed the orbit.

There are conjectures of regular extinction events on 30-60M year intervals, but the data for that isn't strong. https://en.wikipedia.org/wiki/Extinction_event#Patterns_in_f...

Our star system has only a single asteroid belt, so if you are referring to it then the proper phrasing would be "the asteroid belt" (like "the moon" and "the sun"). And no, we (assuming that "we" is the Earth) do not pass through it at all.

If you are suggesting that we are passing through another asteroid belt, like the ones around Vega or Fomalhaut, then the damage done by passing so close to their star would far outpace the damage done by their asteroid belt!

Is there a source for this? I wasn't aware of that, and it sounds interesting.

So New Zealand might not be the best place to bug out to if Australia is a meteor magnet.

We’re a terrible choice for avoiding natural disasters. There is a 75% chance of the Alpine Fault between The Pacific Plate and the Indo-Australian Plate rupturing in the next 50 years and they tend to be earthquakes of magnitude 8+.

On average it ruptures every 291 years (+/- 23), and the last one was in 1717.

https://en.m.wikipedia.org/wiki/Alpine_Fault

The theory is that visitor centers attract meteors, but what is not understood is why the meteors never actually hit them directly, and why so many meteors land in craters.

https://www.reddit.com/r/funny/comments/fgztcd/look_how_clos...

New Zealand like Japan, Indonesia and other places around the pacific ring of fire is very geologically active.

I have only barely felt one earthquake living in Australia in half a century and it was almost imperceptible. I expect the low geological activity is one of the reasons evidence of meteor impacts is well preserved in Australia.

Not that meteor magnets exist, but https://en.wikipedia.org/wiki/List_of_impact_craters_on_Eart... says there are more known impact craters in Europe than Australia.

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