Incoming: The Chicxulub Impactor, Part 3 ― The Impactor & Effects By Stephanie Osborn

Incoming: The Chicxulub Impactor, Part 3 ― The Impactor & Effects

By Stephanie Osborn

The Impactor

Based on the evidence at the impact site, there are quite a few things that can be fairly readily extrapolated about the impactor.

  • Impactor’s estimated velocity: 12.6-73km/s (4,500-26,000km/hr or 2,800-16,300mph)
  • Impactor’s estimated diameter: 9-11km (~5.5-6.8mi) up to 81km (50mi)
  • Impactor’s estimated mass: 0x1015-4.6×1017kg  (2.2×1015-1.0×1018lb)

The generally held view is that the impactor was an asteroid about 10km (6mi) in diameter, traveling at 16-32 km/sec (10-20 miles/sec, or 36,000-72,000mph).

the impact

The Impact

So the impactor comes screaming in at anywhere from 2,800 to as high as 16,000 miles an hour, doesn’t even notice the top, oh, 290 miles of atmosphere, and that last 10 miles of air doesn’t even slow it down. Nor does the relatively shallow water in which it impacts, which, 65 million years ago, covered the entire site.

When the impactor contacted Earth’s surface, it still didn’t slow down, at least not initially. Instead, it punched several miles into the rock. The sudden impact vaporized the impactor as well as substantial quantities of ocean basin and underlying bedrock. Additional quantities of Earth’s crust were liquified and sent into exoatmospheric, suborbital trajectories, only to fall back down, far far away from where it started. Some was probably ejected from its home planet entirely. And the remaining bedrock of the entire region was shattered like fragile glass.

Ground Zero

  • Original crater depth: several miles (exact depth not yet determined; possibly as deep as 25-30mi, per Gulick, et al.)
  • Original crater diameter: 185km (115mi); some estimate 300km (186mi)
  • Temperatures at ground zero: >>10,000ºF, possibly as much as 18,000ºF (~10,000ºC)
  • Yield/KE of impact: at least 1.1×108-1.6×108MT or over 100,000GT

By comparison, the biggest nuke ever detonated on Earth, Tsar Bomba, was 50MT. The Chicxulub impact was, at these numbers, 2 million times as powerful as Tsar Bomba.


The Thermal Blast

If you were close enough to see the impact, it would have been the last thing you ever saw. All life within 1,000km (625mi) would have been incinerated in under 10 seconds.

The Atmospheric Shock Wave

  • Local winds: 900-1000 km/hr (560-625mph)
  • Air blast damage radius: 900-1800km (560-1120mi)
  • Sound of impact: at least 105+ decibels

The Megatsunami

    • Megatsunami height range estimates: 50-305m (~165-1,000ft) [Note that these estimates depend on a given researcher’s initial conditions, therefore the estimates vary widely.]
    • Estimated inland reach: >100km (62mi)


The Seismic Seiche

A seiche is a localized tsunami-like wave akin to a “bathtub slosh.” It is usually generated by the local arrival of one or more earthquake waves.

Extrapolating from the 2011 quake in Tohoku, Japan (mag~9.2), which generated a 1.5m (~5ft) seiche, we can estimate that the seismic waves from the Chicxulub impact generated seiches of 10-100m (33-330ft).

Released Greenhouse Gases

Estimated released greenhouse gases:

      • Carbon dioxide, CO2: ~10 trillion tons (10,000,000,000,000 tons)
      • Carbon monoxide, CO: ~100 billion tons (100,000,000,000 tons)
      • Methane, CH4: ~100 billion tons (100,000,000,000 tons)

And methane is flammable, in itself.

The Aftermath

Core drilling on the peak ring of the crater showed that the topmost layer of debris laid down in the aftermath contained a significant amount of organic material, topped by bits of charcoal; evidently there were significant fires ignited worldwide, and the first days after the cataclysm may well have been a firestorm in many, if not most, places.

After the fires died down, Earth would have entered a “nuclear” winter for at least a year and possibly up to several decades after the impact, thanks to all of the particulate material (dust, soot, smaller ejecta) which was injected into the stratosphere, that then blocked the sunlight. Researchers estimate global temperatures decreased by 2-3ºC (3.5-5.5ºF); some areas dropped as much as 8ºC (14.5ºF). Photosynthesis largely ceased worldwide; plants began to die. As a consequence, herbivores began to starve; subsequently, predators began to starve. The last to die would, presumably, have been the scavengers, though based on the information coming out of the Tanis/Hell Creek dig, no one lasted long enough for there to be a lot of scavenging.

But ash is particulate, and eventually the ash will precipitate out of the atmosphere.

Some of this stratospheric material was in the form of sulfur and nitrogen compounds; as it gradually settled and fell out of the atmosphere, it formed acid rain.

Then the released greenhouse gases took over, and the low temperatures started to soar. This may have lasted for as long as 200,000 years after the K-T boundary.

It gets worse.

Some scientists speculate that such large impacts may generate magma plumes on the antipodal (opposite) side of Earth in the long term. This is generally not considered probable by mainstream researchers. It must be admitted, however,, that the shock waves would indeed converge on the opposite side of the planet; whether it created additional problems or not would likely depend upon the magnitude/amplitude of the shock waves, and whether the timing was such that they interfered constructively or destructively. In any case, the shock waves probably set off existing volcanoes, in a kind of planetary paroxysm.

It is flagrant, screaming understatement to say that the aftermath would not have been pleasant for any survivors.

Next up: What, where, and how hard?


For more details, check out INCOMING! The Chicxulub Impactor by Stephanie Osborn on Kindle and Nook.



And check out Stephanie’s fiction!

CAMPBELL: The Sigurdsen Incident (Childers Universe Book 6)



Captain Mary Rao, Jablonka’s planetary tactical officer, seems to be under the gun from all angles, but neither the Sigurdsen Base military police nor the counter-intelligence investigations personnel believes that it’s anything more than a confluence of accidents.

Lieutenant William Campbell of the CSF Intelligence Division believes differently. What he doesn’t know is who or why.

And if he can’t figure it out soon, he could die with her.

56 thoughts on “Incoming: The Chicxulub Impactor, Part 3 ― The Impactor & Effects By Stephanie Osborn

  1. All of the drawings I’ve seen of the impact site show it as more or less round, which suggests to me that the trajectory was pretty much straight down, centered on the planet.

    Statistically, the likelihood of a glancing blow would be much higher. Though I’m not sure the end result would have been much different.

    1. Look at the craters on the moon. See many oblong ones? Those impacts could not have ALL been head-on. A round crater is simple what usually happens.

      1. A few decades ago, I saw an article on this. The author suggested taking a tray (cake pan) full of powder (flour, if memory serves) and throwing things at it at various angles. The thesis (and I didn’t try it myself) was that the impact craters would be round, regardless of the angles (assuming the incoming material was more-or-less round, to a very rough approximation. Cubes should work that way, probably not dominos.).

        1. I think I saw someone do this; I can’t remember if it was a science show or a movie like “Deep Impact.”

          And I guess I finished out of the running for the “Hellbender” contest.

    2. OMG!!! What if that means it was a TARGETED ATTACK?!?!!?! Aliens who were afraid that dinosaurs would one-day reach for the stars and EAT THEM?!?!

      (Sorry, it’s Halloween and I’m sitting at my desk at work with pink bunny ears and a pink fluffy tail. Kinda makes it hard to take anything seriously)

      1. Oh, come on, Ryk Spoor’s book ‘Boundary’ was NOT a documentary…

        All of the drawings I’ve seen of the impact site show it as more or less round, which suggests to me that the trajectory was pretty much straight down, centered on the planet.

        Think about it. If a 10-KM spherical rock (for simplicity) came in at a 30° angle, the distance from the point where the bottom edge touched ground, and where the top edge reached ground level, would be about 20 KM.

        The crater was over 100 KM in diameter.

        It would be centered at the point where most of the kinetic energy dumped, and would obliterate any trace of the actual rock’s footprint. That is why almost all impact craters are round.
        Mollari: “Everyone is cute! But in purple, I’m stunning!” [collapses on the table]
        Vir: “Ah! He has become one with his inner self!”
        Garibaldi: “He’s passed out.”
        Vir: “That too.”

        1. Probably total ignorance here (because yes, I freely admit that I am ignorant about space stuffs), but if something were to come in at too shallow an angle, it would more likely bounce off rather than hit the ground (or is that a dumb movie thing? See ignorance comment above).

          1. would depend on the size of the item, but then big enough and just getting near will do kilotons of damage even without a contact hit. Sorta like a bigger version of Tunguska.

        2. [shrug] If I shoot at a pumpkin, I can definitely tell the difference in impact crater between a centered and glancing shot.

          1. Try shooting into a large, foot-deep container of unset cement. Nearly liquid mud, very wet sand, or a half cubic yard of wet silt should work too. Tempted to set up something in my FEL bucket and shoot at a 45 degree angle using BB, .22 or .38. Should be deep enough and dense enough to both stop the bullets and to not ding up the bucket. I know, it’s not like a precision ballistics lab.

            Note: None of those calibers penetrate more than 6 inches into the sand backstop on my shooting range, so a foot deep media in the FEL bucket should be 4 times more media distance than necessary, especially impacting at a 45 degree angle.

            1. The ejecta tends to be offset if it’s a shallow angle, but the crater often does tend toward circular, especially in an instance where the rock is actually flowing, let alone the water around/above it.

          2. I recall seeing this tested and they were using bb sized objects going way faster than a bullet and even shallow angles were quite close to round but the ejecta patterns were different until it was near glancing

            1. “and they were using bb sized objects going way faster than a bullet ”

              Aw man, now you’re just being mean. Trying to give me an excuse to build a rail gun, aren’t you?

              1. they were using vacuum and compressed nitrogen iirc. A bit like the supersonic ping pong ball method
                Though I bet that kid who built a rail gun in his folks garage might have some ideas. Caps sometime still go Boom, but his little aluminum pellets have gotten very fast

      2. You’re dressed up as Anya from “Bufffy the Vampire Slayer?”

        ANYA: I found one of those 24-hour places for coffee. Remember that bookstore? Well they became one of those books-and-coffee places, and now they’re just coffee. It’s like evolution, only without the getting-better part.
        6×03, “After Life”

    3. I’d think that to get a glancing blow speeds would need to approach a fair percentage of escape velocity. At lower speeds gravity is going to suck it in and you’ll get something more circular from the impact.

      1. There are meteors which skim the fringes of the atmosphere and skip off.

        Escape velocity for Earth is about 7 miles per second. If you could drop an object from an immense height, a million miles perhaps, by the time it fell to Earth it would be traveling at something very close to escape velocity.

        Also, consider that the Earth’s own orbital velocity is around 20 miles per second. Any orbiting objects nearby will have a similar velocity, depending on the shape of the orbit. To bring something close to Earth it has to have some velocity toward it to begin with. Then mutual gravitational attraction takes over.

        1. >>If you could drop an object from an immense height, a million miles perhaps, by the time it fell to Earth it would be traveling at something very close to escape velocity.<<

          If you could drop an object AND THERE WAS NO ATMOSPHERE. Even meteors tend to reach terminal velocity if they're under a certain size.

          One million miles out is roughly four times lunar distance. There's a whole lotta "IF" in that setup.

  2. Stephanie. Super interesting! I had never heard any estimates of the size of the Impactor (mostly because I didn’t get around to looking it up)

    Secretly, while I was reading this, my brain was translating it to how an old guy might turn it into a story to tell sitting around a camp fire. “And it fell from the sky. It was 50 or so miles around, and going thousands of miles per hour! When it hit, it flattened everything within a thousand miles and turned the earth around it to liquid, and dug a hole maybe 50 miles down!”

    1. Considering the heat and blast, that would have to be one heck of a shelter for the old geezer to be in. We don’t have any aircraft that could survive the atmospheric conditions close enough to have seen the actual blast; so I’d have to postulate someone out in space watching.

      Even observing such a catastrophe from the International Space Station could be an iffy proposition. The ISS orbits a smidge above 250 miles up. That’s low enough for the initial back blast to wipe it out if it flew through it, and for any exoatmospheric ejecta to take it out either rising or coming back in. I suspect that the blast would also have caused atmospheric waves high enough that would push up dense enough air to retard the orbit, if not rip off the solar panels or even rip apart the station itself, if dense enough, and a steep enough density gradient.

      But that kind of fluid dynamics and math is way above my pay grade.

      1. Pfaww… Perhaps you don’t understand old guys and story telling. Just because the old feller tells a story doesn’t mean he was actually THERE.

        I once heard an old guy, who was an incredible story teller, tell the story of the Donner party. It was INCREDIBLE. Camping in the mountains, sitting around the camp fire with a few good friends in the middle of summer, and that guy had us all shivering, FEELING the cold as it set in and the food ran out, and the horror of “who goes first?” I account myself as an “ok” story teller. I’m sure if I hadn’t heard some of the really good story tellers that I have, I would consider myself good at it, but man I can’t even hold a candle to some of those guys.

  3. Interesting story, and well-written, Ms. Osborn. And the magnitude of the event and its probable consequences are horrific.

    But I gotta tell ya. Every time I get to the bottom and see that hamburger-munching dinosaur glancing behind itself, I crack up. I’d love to read that guy’s story! 🙂 (Well, I guess the last chapter would be kind of a downer.)

    1. George was just a timid little burrowing guy, about the size of a modern woodchuck, and built similarly. But he was rather agnostic about his diet; seeds, vegetation, small arthropods, even carrion would satisfy his hunger.

      Yesterday, the world heaved. George woke up terrified in his burrow. Bouncing off the walls and the ceiling as half the burrow collapsed. He has only just started digging back out when a massive roar thundered down into the soil, before fading away, and leaving the dirt and air so mysteriously hot that George was panting for hours.

      George finally recovered enough and recommenced digging himself out. It didn’t take as long as he thought as he broke through three quarters of the way up to a new unrecognizable surface that looked pulverized and baked. His mouth dropped open. None of the food plants he normally ate were in view. But something tantalized his furry nostrils. He turned and spied a huge mound. It was one of the king lizards that terrorized him and his kind. It lay there, beaten, roasted, and dead. The remains of a burger still clutched in its dainty foreclaws.

    2. Don’t give me more ideas! I’m trying to get down what I got, now.

      (Okay, I might have to write that one as a short story.)

      But yeah, my husband does a lot of my covers, and he’s got a warped sense of humor, which I love. I saw that comp image he made for me, and laughed my head off, then said, “That’s my cover!”

      1. News Flash! Paleontologist Jack Horner discovers 10 fool long grill spatula buried with tyrannosaurus skeleton! Dr. Horner is still unable to explain the existence of a truck-sized Webber grill found nearby in the same rock strata. Graduate students refuse to admit to prank.

  4. Every time I read any of this (bought the book already 🙂 ) I have to go look for an impact calculator. Like the one from To get somewhat close to the numbers and effects Stephanie talks about, putting it in the Yucatan again (I realize it is really really really unlikely to hit there a 2nd time. Just because) And how far from here. Had to go to an iron asteroid, moving 24km, water depth 100m, Yeah…. so I live in Alaska. It’d shatter the windows in the house. Oh wait, the 10.3 Earthquake, did that already when it flattened the house. 3.75 hours before the air-blast got there. Don’t think the tsunami would matter much but maybe if it was high tide.

    The whole thing is nightmare fuel! Really well written nightmare fuel.

    1. Thank you very much. I tried very hard to make it easily understandable. I want readers to envisage what happened.

      To me, the scary part of it all is that it DID happen. The details are all extrapolated from the conditions and state of the impact site and surrounds. No part of this is made up.

      1. It seems more amazing that such events are so rare. Perhaps we owe Luna a debt of thanks for taking so many hits on our behalf?

          1. Agreed with both you and RES, thanks to the Moon (for many reasons, not just taking the hits) but also to big ol Jupiter in this context. The giant Sweeper of the inner system. Shoemaker – Levy Nine for the win anyone? And that was just in our lifetime. With a fireball the size of Earth when the different parts hit.

  5. OT, but I’m going to try NaNoWriMo again this year. This is my sixth try, haven’t finished yet, I have an inner editor which has been shutting me down hard a few thousand words in; but I’m wiser to its tricks. if any Huns or Hoydens feel like they want to volunteer as a writing buddy, I go by the same handle there as I do here.

  6. FYI, a paper I discovered after sending the blog articles to Sarah shows evidence that the initial megatsunami was WORLDWIDE. Meaning that all ocean basins were affected, and the thing may have been as much as a mile high, at least initially.

    Contrast that with the Boxing Day tsunami, which only affected the Indian Ocean and coastlines.

  7. Two other effects I’ve seen mentioned:

    Most of the ejecta falls back, re-entering the atmosphere over the next 10 to 20 hours as a world-wide meteor storm, billions of meteors incoming at velocities up to 10 KPS, which heats the upper atmosphere to a toasty 700° (370 C) and gives all the surviving critters a preview of Thanksgiving from the turkey’s perspective.

    Meanwhile, the entire ocean is pouring into the 100-mile-wide lava pit, blasting millions of tons of steam into the air. It’s the sauna from Hell.
    Nobody expects the Spanish Inquisition!!

      1. No. And from what I’ve read, none of the animals larger than a medium sized dog survived. Since birds survived, and not all of those animals were burrowers, or mid-oceanic swimmers, it’s likely there were multiple locations around the planet where the temperatures were actually fairly moderate.

        Looking on Quora shows the following estimates for human survival (and we’re at the top end of size for survival of the KT impactor)

        Dry air: 120+ °C (248+ °F) short term, 70+ °C (158+ °F) long term (with access to water at cooler temperatures).
        Tropical air: 60+ °C (140 °F) short term, 47 °C (117 °F) long term.
        Saturated air: 48 °C (118 °F) short term, 35 °C (95 °F) long term.
        Water: 46° C (115 °F) short term, 41°C (106 °F) long term.

        I’d say it’s a sure bet that temperatures did not exceed 248 F in many places around the globe, and more likely did not exceed 120 F in those places, since birds don’t seem to survive at all when it exceeds that.

  8. I am sorry to point out there is an error in the speed of the impactor.

    “◾Impactor’s estimated velocity: 12.6-73km/s (4,500-26,000km/hr or 2,800-16,300mph)”

    I believe you intended it should read “45,000-260,000km/hr or 28,000-163,000mph”

    I noticed when I first read this but had forgotten to mention it by the time I finished the whole installment.

  9. Small nit: you mention three gases and add that methane is flammable, which suggests that the other two aren’t. In fact, CO is also flammable.

    1. True. But methane, being a fuel in and of itself, is rather of more interest in this particular consideration. Perhaps HIGHLY flammable should have been the wording.

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