# The Cretaceous-Paleogene extinction event had to have been crazy fast, right? **URL:** \ **Category:** In My Humble Opinion\ **Tags:** science-math\ **Created:** [August 2, 2026, 3:55pm UTC](https://boards.straightdope.com/t/the-cretaceous-paleogene-extinction-event-had-to-have-been-crazy-fast-right/1032096 "2026-08-02T15:55:38Z")\ **Posts on this page:** 20\ **Page:** 1
**Author:** ![steronz](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/steronz/32/11765_2.png) [@steronz](https://boards.straightdope.com/u/steronz)\ **Post date:** [August 2, 2026, 3:55pm UTC](https://boards.straightdope.com/t/the-cretaceous-paleogene-extinction-event-had-to-have-been-crazy-fast-right/1032096/1 "2026-08-02T15:55:38Z")
I’ve been catching up on a lot of the science that’s happened in 30 years since I had a formal science class, especially genetic studies and fossils that support evolution in really remarkable ways. Some of the more fascinating examples come from evolutionary paths since the [Cretaceous-Paleogene extinction event](https://en.wikipedia.org/wiki/Cretaceous%E2%80%93Paleogene_extinction_event). Keep in mind that even though the [Alvarez hypothesis](https://en.wikipedia.org/wiki/Alvarez_hypothesis) was present in the “Dinosaurs for early readers” books I loved in the '80s, it was always present as a hypothesis among others. Even [in this thread from 1999](https://boards.straightdope.com/t/dinosaur-extinction/16777/44) that Discourse recommended to me, it’s treated with some skepticism. Now, of course, with more evidence collected about the [Chicxulub impact](https://en.wikipedia.org/wiki/Chicxulub_crater) it’s widely accepted. Likewise, the theories that whales evolved from land mammals and birds evolved from dinosaurs were considered possibilities and are now supported by a mountain of genealogical and fossil evidence. [What still seems up for debate](https://arstechnica.com/science/2026/07/dust-cloud-from-dino-killing-asteroid-charbroiled-the-earth/), though, is how _quickly_ it happened. Where the [Permian-Triassic extinction event](https://en.wikipedia.org/wiki/Permian%E2%80%93Triassic_extinction_event) taking 100,000+ years of volcano-induced climate change, scientists are starting to support theories that the Cretaceous extinction happened in 10,000 years or less, with some proposing that it was much, much less. I find their arguments compelling. What I’m learning now is that avian dinosaurs that we would recognize as “birds” today (lay eggs, have feathers, are sometimes capable of flight, have beaks) evolved long before the extinction event. Likewise, mammals hard started to diversify. And yet, the only species that survived the event were – small, burrowing, omnivorous, scavengers. Chickens and rats, basically. Swamp critters in a similar ecological niche also survived, and in the oceans, everything in the water column died except for bottom feeders that would eat decaying animals. As for plants, with few exceptions only plants with hardy seeds survived – the type that survive forest fires today, for instance. To me, this paints a picture of an almost immediate famine. Material would have been ejected from the asteroid impact, blocking out the sun and acidifying the oceans, but then almost immediately would have started settling back to the ground. The first year would be brutal – all plant life dying in the first few weeks, primary consumers starving after that, secondary consumers and on. Months, perhaps, before everything was dead except the species that could survive on detritus, dead animals, and seeds. But if that went on too long, nothing would have survived, so it seems plausible that the next year saw seeds sprouting, the skies clearing, and oxygen supplies in the ocean recovering. That process may have taken hundreds or thousands of years to return to normal, but the hardy species that survived the first few months would have been able to survive through that period. The alternative theory, I suppose, is that the impact made the conditions bad but not completely inhospitable, and plesiosaurs and triceratops continued to live for hundreds or thousands of years while competing with each other for dwindling resources until more conventional extinctions happened one by one. I’m not smart enough on this to know if this makes sense but my uninformed gut can’t come to terms with this. Anyway, I’m sure I sound like a goober talking about things I know little about, but is there any reason to doubt the idea that the extinction event was really mostly done in 1-2 years? As crazy as that might seem in geological terms? ---
**Author:** ![PlaceboTarget](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/placebotarget/32/1073_2.png) [@PlaceboTarget](https://boards.straightdope.com/u/PlaceboTarget)\ **Post date:** [August 2, 2026, 5:21pm UTC](https://boards.straightdope.com/t/the-cretaceous-paleogene-extinction-event-had-to-have-been-crazy-fast-right/1032096/2 "2026-08-02T17:21:37Z")
I think I saw an article about it early today. It claimed the space rock was 10 km in diameter and the dinosaurs became extinct in a matter of hours. ---
**Author:** ![Darwins\_Finch](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/darwins_finch/32/20304_2.png) [@Darwins\_Finch](https://boards.straightdope.com/u/Darwins_Finch)\ **Post date:** [August 2, 2026, 5:26pm UTC](https://boards.straightdope.com/t/the-cretaceous-paleogene-extinction-event-had-to-have-been-crazy-fast-right/1032096/3 "2026-08-02T17:26:18Z")
So…there was a lot going on at the K-Pg boundary. There are three main ‘events’ that all contributed to the end-of-Cretaceous extinctions: 1. The Maastrichtian Regression: this was a global lowering of sea levels, caused by a decrease in the amount of mid-oceanic ridge activity; that is, uplifting in the oceans decreased, which resulted in sinking sea floors, and sea levels along with them. The result would have been major environmental effects, especially along coastal regions, along with global changes in weather patterns, thanks to changing currents and such. The effects of this would have taken place over a few million years. 2. Deccan Traps: there was a period of intense volcanism, centering around what is now western India, starting around 500,000 yrs or so before the end of the Cretaceous. As one would expect, this resulted in some significant climate changes in various regions (some areas got cooler, some warmer). In combination with the regression mentioned above, these two events alone would have triggered a mass extinction event, and were responsible for a fair number of taxonomic casualties. As noted by the timing, the extinctions brought about by this aspect would have played out over half-a-million years. 3. The Chicxulub impact: the effects here would have played out on various timescales. There are a number of ‘day one’ events that would have triggered mass die-offs: tsunamis, earthquakes, hurricane-force winds, etc. Most of the death and destruction caused by these events would have been localized to the region of the impact itself. There was also a significant ‘heat shock’ - atmospheric heating caused by a mountain of rock blasting through the atmosphere. Anything above ground would have been flash-fried; anything underground and in deep-enough water would have survived this aspect well enough (though they obviously would have other problems soon enough…). This seems to have been one of the primary instantaneous killers of large terrestrial critters. Then, you get secondary global forest fires as a result, which, along with the impact itself, would have put a whole lot of ash, dust, and other debris into the atmosphere. So these are all relatively quick - days to weeks at most for these effects to be felt. But, now, because of all the crap in the atmosphere, you get global cooling (so-called ‘impact winter’) for the next several years (current estimates are somewhere between 3 and 16 years). This seems to have been the most significant killer, in terms of mass extinction. But then you also now have a lot of greenhouse gases (exacerbated by the aforementioned Deccan Traps volcanism which is happening simultaneously) in the atmosphere, which results in global warming. Increased temperatures (~5°C) appear to have lasted for around 100k years following the event. As a result of the various events, then, it can be difficult to attribute any one effect in all of this to the extinction of any particular clade, and thus it can be difficult to figure out how long it took a given clade to die off. Some groups would have been wiped out immediately (e.g., most North American non-avian dinosaurs), others lingering for several millennia. ---
**Author:** ![PlaceboTarget](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/placebotarget/32/1073_2.png) [@PlaceboTarget](https://boards.straightdope.com/u/PlaceboTarget)\ **Post date:** [August 2, 2026, 5:33pm UTC](https://boards.straightdope.com/t/the-cretaceous-paleogene-extinction-event-had-to-have-been-crazy-fast-right/1032096/4 "2026-08-02T17:33:47Z")
Here’s an article supporting the idea of a superfast extinction: [Dinosaurs died out within hours, new study suggests | Popular Science](https://www.popsci.com/science/how-fast-did-dinosaurs-go-extinct/) The asteroid was six‑mile‑wide. It released energy over a billion times stronger than the Hiroshima and Nagasaki blasts (causing tsunamis, hurricane‑force winds, and launching trillions of tons of debris into the atmosphere). The most terrible result was not only the falling superheated spherules that ignited widespread fires, but also vaporized rock. This vaporized rock formed a thick atmospheric blanket that heated Earth’s surface to lethal levels (causing instant death and spontaneous global wildfires). This firestorm wiped out most terrestrial life rapidly. And the lingering dust locked sunlight for years (causing further death). ---
**Author:** ![Tamerlane](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/tamerlane/32/7602_2.png) [@Tamerlane](https://boards.straightdope.com/u/Tamerlane)\ **Post date:** [August 2, 2026, 5:41pm UTC](https://boards.straightdope.com/t/the-cretaceous-paleogene-extinction-event-had-to-have-been-crazy-fast-right/1032096/5 "2026-08-02T17:41:31Z")
> [@steronz](#): > > Keep in mind that even though the [Alvarez hypothesis](https://en.wikipedia.org/wiki/Alvarez_hypothesis) was present in the “Dinosaurs for early readers” books I loved in the '80s, it was always present as a hypothesis among others. Even [in this thread from 1999](https://boards.straightdope.com/t/dinosaur-extinction/16777/44) that Discourse recommended to me, it’s treated with some skepticism. In this thread in 2022 I discussed this as [an example of a controversial idea that prevailed](https://boards.straightdope.com/t/how-to-distinguish-between-minority-opinions-and-misinformation/958690/21). As I noted when I was taking first semester biology in Fall of 1985 it was treated as a controversial hypothesis and regarded skeptically by the biologist/paleontologist community. MrDibble then noted by the time he was taking geology in 1989 it was regarded as the leading hypothesis and by around 1995 was the dominant one. I would say Alvarez ended up largely winning the debate (though there is still arguments over it, there always are). ---
**Author:** ![blondebear](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/blondebear/32/1022_2.png) [@blondebear](https://boards.straightdope.com/u/blondebear)\ **Post date:** [August 2, 2026, 5:50pm UTC](https://boards.straightdope.com/t/the-cretaceous-paleogene-extinction-event-had-to-have-been-crazy-fast-right/1032096/6 "2026-08-02T17:50:55Z")
The American Museum of Natural History has an exhibit that might be of interest: [“Impact: The End of the Age of Dinosaurs”](https://www.instagram.com/p/DRAQgxaDCsM/?img_index=3) ---
**Author:** ![MrDibble](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mrdibble/32/114_2.png) [@MrDibble](https://boards.straightdope.com/u/MrDibble)\ **Post date:** [August 2, 2026, 6:53pm UTC](https://boards.straightdope.com/t/the-cretaceous-paleogene-extinction-event-had-to-have-been-crazy-fast-right/1032096/7 "2026-08-02T18:53:58Z")
> [@Darwins\_Finch](#): > > Most of the death and destruction caused by these events would have been localized to the region of the impact itself. I think the Tanis site shows that this is not the case. We can assume an _at least_ 3000 km radius of destruction around Chicxulub based on that. ---
**Author:** ![Darwins\_Finch](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/darwins_finch/32/20304_2.png) [@Darwins\_Finch](https://boards.straightdope.com/u/Darwins_Finch)\ **Post date:** [August 2, 2026, 7:18pm UTC](https://boards.straightdope.com/t/the-cretaceous-paleogene-extinction-event-had-to-have-been-crazy-fast-right/1032096/8 "2026-08-02T19:18:12Z")
By ‘local’, I meant (but failed to clarify) more along the lines of North America, Central America, and northern South America, as opposed to being global effects. Late Cretaceous Asian sauropods, for example, were probably not killed outright by effects such as these. ---
**Author:** ![billy-jack](https://avatars.discourse-cdn.com/v4/letter/b/ac91a4/32.png) [@billy-jack](https://boards.straightdope.com/u/billy-jack)\ **Post date:** [August 2, 2026, 7:35pm UTC](https://boards.straightdope.com/t/the-cretaceous-paleogene-extinction-event-had-to-have-been-crazy-fast-right/1032096/9 "2026-08-02T19:35:35Z")
I wonder how far the tidal wave would have traveled inland in the areas surrounding the Gulf of Meximerica. ---
**Author:** ![MrDibble](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mrdibble/32/114_2.png) [@MrDibble](https://boards.straightdope.com/u/MrDibble)\ **Post date:** [August 2, 2026, 7:38pm UTC](https://boards.straightdope.com/t/the-cretaceous-paleogene-extinction-event-had-to-have-been-crazy-fast-right/1032096/10 "2026-08-02T19:38:28Z")
Depends on if you fall on the high vs moderate temperature side of the ejecta reentry heating debate. Me, I’m on the high side. See this recent paper: [https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2026JG009837](https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2026JG009837) Further discussion of it here: > **[Chicxulub Dust Amplified Impact Heat 3.5x, Potentially Killing Dinosaurs...](https://www.techtimes.com/articles/321861/20260728/chicxulub-dust-amplified-impact-heat-35x-potentially-killing-dinosaurs-within-hours.htm)** > > Dinosaur extinction heat pulse dust: Purdue University researchers found that fine silicate dust from the Chicxulub asteroid amplified surface heat flux 3.5x, potentially killing large terrestrial animals within the first hour or two and pointing to... As far as I’m concerned, your hypothetical Asian sauropds died of heatstroke a few hours after the impact, if they didn’t get burned outright. ---
**Author:** ![Darwins\_Finch](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/darwins_finch/32/20304_2.png) [@Darwins\_Finch](https://boards.straightdope.com/u/Darwins_Finch)\ **Post date:** [August 2, 2026, 7:44pm UTC](https://boards.straightdope.com/t/the-cretaceous-paleogene-extinction-event-had-to-have-been-crazy-fast-right/1032096/11 "2026-08-02T19:44:15Z")
Also, a quick note, since this is about extinction: while Tanis does show that many individuals were likely killed by seiche waves caused by massive earthquakes, that doesn’t necessarily indicate that entire species were thus wiped out by them, at that location. There were several new species identified in the assemblage, but we need to be careful about assuming that means those species also went extinct at that time. And we know that the larger clades to which various fish found at the site belonged to did survive. ---
**Author:** ![Darwins\_Finch](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/darwins_finch/32/20304_2.png) [@Darwins\_Finch](https://boards.straightdope.com/u/Darwins_Finch)\ **Post date:** [August 2, 2026, 7:47pm UTC](https://boards.straightdope.com/t/the-cretaceous-paleogene-extinction-event-had-to-have-been-crazy-fast-right/1032096/12 "2026-08-02T19:47:09Z")
Almost certainly; I did mention the heat shock aspect (and separated it from the tsunamis, earthquakes, etc.), as a likely “day one” extinction cause. ---
**Author:** ![MrDibble](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mrdibble/32/114_2.png) [@MrDibble](https://boards.straightdope.com/u/MrDibble)\ **Post date:** [August 2, 2026, 7:47pm UTC](https://boards.straightdope.com/t/the-cretaceous-paleogene-extinction-event-had-to-have-been-crazy-fast-right/1032096/13 "2026-08-02T19:47:17Z")
Tanis was a few to a few tens of kilometers inland from the Western Interior Seaway. ---
**Author:** ![MrDibble](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mrdibble/32/114_2.png) [@MrDibble](https://boards.straightdope.com/u/MrDibble)\ **Post date:** [August 2, 2026, 7:54pm UTC](https://boards.straightdope.com/t/the-cretaceous-paleogene-extinction-event-had-to-have-been-crazy-fast-right/1032096/14 "2026-08-02T19:54:49Z")
Sure. I’m just saying it’s in like Hour 3 rather than Hour 24 of that same day, so I don’t really see much point in separating that out from other direct impact effects (vs say global cooling, starvation or acid rain) ---
**Author:** ![wolfpup](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/wolfpup/32/10618_2.png) [@wolfpup](https://boards.straightdope.com/u/wolfpup)\ **Post date:** [August 2, 2026, 8:13pm UTC](https://boards.straightdope.com/t/the-cretaceous-paleogene-extinction-event-had-to-have-been-crazy-fast-right/1032096/15 "2026-08-02T20:13:07Z")
There’s also a good discussion we had here several years ago, link below. In the second post of that thread, I provided a link to an excellent _New Yorker_ article about the Tanis site, which I believe also provides a fascinating account of what happened on that fateful day. The _New Yorker_ is semi-paywalled but allows free access to a very small number of articles every month. > [@The KT impact: deaths on the day found in Dakota](https://boards.straightdope.com/t/the-kt-impact-deaths-on-the-day-found-in-dakota/831757): > > BBC story [here](https://www.bbc.co.uk/news/science-environment-47755275). Scientists have found creatures that were killed on the day of the impact and were immediately covered by mud and thus preserved as fossils. Amazing. ---
**Author:** ![Darwins\_Finch](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/darwins_finch/32/20304_2.png) [@Darwins\_Finch](https://boards.straightdope.com/u/Darwins_Finch)\ **Post date:** [August 2, 2026, 8:17pm UTC](https://boards.straightdope.com/t/the-cretaceous-paleogene-extinction-event-had-to-have-been-crazy-fast-right/1032096/16 "2026-08-02T20:17:57Z")
Mostly because, as Day One events go, the heat shock aspect likely resulted in more outright extinctions than did the assorted aftermath events like earthquakes & tsunamis. That’s all. ---
**Author:** ![snowthx](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/snowthx/32/10660_2.png) [@snowthx](https://boards.straightdope.com/u/snowthx)\ **Post date:** [August 3, 2026, 8:57pm UTC](https://boards.straightdope.com/t/the-cretaceous-paleogene-extinction-event-had-to-have-been-crazy-fast-right/1032096/17 "2026-08-03T20:57:32Z")
> [@PlaceboTarget](#): > > This firestorm wiped out most terrestrial life rapidly. And the lingering dust locked sunlight for years (causing further death). This is what has me wondering as well. If animals of the time were killed in a short period of time, how long before they rotted away? Assuming the rate of decay is similar as it is today, I would guess anything killed the day of the impact would be gone in a matter of weeks. So, what did the survivors subsist on after that if sunlight was locked down for years? Bones? If some species survived the impact and slowly died off, what were they subsisting on during the turmoil? ISTM there must have been some plant life doing okay for a while, otherwise if everything shut down, then the chickens and rats would have eventually starved as well, right? Even hearty seeds eventually lose their nutritional value. I mean, how long did an asteroid-caused carcass exist before it decayed away to dust and couldn’t nourish anything at all? ---
**Author:** ![Alessan](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/alessan/32/465_2.png) [@Alessan](https://boards.straightdope.com/u/Alessan)\ **Post date:** [August 3, 2026, 9:56pm UTC](https://boards.straightdope.com/t/the-cretaceous-paleogene-extinction-event-had-to-have-been-crazy-fast-right/1032096/18 "2026-08-03T21:56:55Z")
My guess? Enough plants survived, somewhere in the world. Not a lot, but a valley here, a square mile of scrub there - enough to sustain a scattered bunch of tiny biosystems, which eventually seeded the rest of the planet. ---
**Author:** ![puzzlegal](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/puzzlegal/32/3827_2.png) [@puzzlegal](https://boards.straightdope.com/u/puzzlegal)\ **Post date:** [August 3, 2026, 10:15pm UTC](https://boards.straightdope.com/t/the-cretaceous-paleogene-extinction-event-had-to-have-been-crazy-fast-right/1032096/19 "2026-08-03T22:15:58Z")
Nuts and grain can be edible for years. I imagine there was some cannibalism. Some of those nuts and seeds succeeded in sprouting, presumably. ---
**Author:** ![MrDibble](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mrdibble/32/114_2.png) [@MrDibble](https://boards.straightdope.com/u/MrDibble)\ **Post date:** [August 4, 2026, 7:15am UTC](https://boards.straightdope.com/t/the-cretaceous-paleogene-extinction-event-had-to-have-been-crazy-fast-right/1032096/20 "2026-08-04T07:15:55Z")
> [@snowthx](#): > > So, what did the survivors subsist on after that if sunlight was locked down for years? Mushrooms… [https://publichealth.jhu.edu/2026/fungal-surges-marked-cretaceous-mass-extinction-that-ended-age-of-dinosaurs](https://publichealth.jhu.edu/2026/fungal-surges-marked-cretaceous-mass-extinction-that-ended-age-of-dinosaurs) [Next page](https://boards.straightdope.com/t/the-cretaceous-paleogene-extinction-event-had-to-have-been-crazy-fast-right/1032096.md?page=2)