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Earth Science

Scientists Discover New Evidence of the Asteroid That Killed Off the Dinosaurs 54

Posted by BeauHD from the blast-from-the-past dept.
An anonymous reader quotes a report from The Wall Street Journal: Drilling into the seafloor off Mexico, scientists have extracted a unique geologic record of the single worst day in the history of life on Earth, when a city-sized asteroid smashed into the planet 65 million years ago, wiping out the dinosaurs and three-quarters of all other life. Their analysis of these new rock samples from the Chicxulub crater, made public Monday, reveals a parfait of debris deposited in layers almost minute-by-minute at the heart of the impact during the first day of a global catastrophe (Warning: source paywalled; alternative source). It records traces of the explosive melting, massive earthquakes, tsunamis, landslides and wildfires as the immense asteroid blasted a hole 100 miles wide and 12 miles deep, the scientists said. The sediments also offer chemical evidence that the cataclysm blew hundreds of billions of tons of sulfur from pulverized ocean rock into the atmosphere, triggering a global winter in which temperatures world-wide dropped by as much as 30 degrees Fahrenheit for decades, the scientists said. "The asteroid blasted a cavity between 25 and 30 miles deep in the first seconds of impact, creating a boiling cauldron of molten rocks and super-heated steam," reports The Wall Street Journal, citing the scientists' interpretation of the rock. "Rebounding from the hammer blow, a plume of molten rock splashed up into a peak higher than Mount Everest. Within minutes, it collapsed into itself, splashing gigantic waves of lava outward that solidified into a ring of high peaks, the scientists said."

"About 20 minutes or so later, sea water surged back over the newly formed peaks, covering them in a blanket of impact rocks, the scientists said. As minutes became hours, waves choked with shards of volcanic glass and splintered rock rippled back and forth, coating the peaks in a layer of impact rock called suevite, the scientists said. As the hours passed, the backwash of waves added more and more finely graded debris. At the very top of the rock core, the scientists detected traces of organic matter and charcoal."

The study was published today in the journal PNAS.
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Scientists Discover New Evidence of the Asteroid That Killed Off the Dinosaurs More

Scientists Discover New Evidence of the Asteroid That Killed Off the Dinosaurs

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  • As science journalism goes, this isn't too bad. I had originally considered mostly smake/debris as the cooling mechanism, but yea aresolized sulfur compounds would cool things down for years.

    • Re: (Score:1)

      by Anonymous Coward
      Interesting how the birds survived this. One would assume it's because they were able to fly away from the areas that were devastated the most, and migrate to the areas that were still able to support some semblance of a biosphere for the subsequent decade or two. Anything that couldn't fly or burrow probably perished.

      • Interesting how the birds survived this. One would assume it's because they were able to fly away from the areas that were devastated the most, and migrate to the areas that were still able to support some semblance of a biosphere for the subsequent decade or two. Anything that couldn't fly or burrow probably perished.

        Birds are warm blooded which helps when things get colder- and yes, some dinosaurs were too- but birds were also able to travel further distances to reach new food sources and most birds would have been smaller: (when resources get scarce, having lesser food requirements means you're less likely to starve).

        I heard another theory from a widely mocked French scientist the other day who theorized that large dinosaurs died out because of climate change, and large lakes drying up where the dinosaurs lived. His

      • I would assume birds survived for a combination of factors, not only that they could fly away from immediate danger and re-locate to richer ecosystems, but also that they fed on more widespread prey such as insects and rodent ancestors, and by then were likely warm-blooded [youtube.com] and covered in feathers for isolation.

      • Birds seem to have evolved from some Dinosaur linage. I expect replaceable feathers, warm blooded, flight probably all helped them survive. While Mammals, Lizards, Snakes probably hunkered down under ground. Aquatic Reptiles and Fish had a degree of protection from the ocean (Larger Aquatic Reptiles probably couldn't handle the drop in biodiversity though)

        One of the aspects the differentiate dinosaurs from lizards and other reptiles, is the fact their legs are positioned upright while lizards and turtles a

      • Re:Well now! (Score:5, Informative)

        by greythax ( 880837 ) on Tuesday September 10, 2019 @11:06AM (#59177430)

        There were several paths to surviving extinction. It's helpful to imagine the circumstances. While the impact was vast and terrible, it didn't just flatten the species like an h-bomb and have done with it. The full extinction event seems to have taken thousands of years.

        The day of the impact would have been a very bad day, but the following year or two would have been even worse. First, you have to survive the cold which was likely pretty severe for the first few months. It's not as if winter hadn't been invented yet, so most species would have had adaptation strategies. The real test would have come when the plants didn't start growing back. Being a bird, with warm blood and eating insects, which get their food from dead plants, life would have been much better than for most species. Being a burrowing mammal who ate seeds was also a pretty good niche. Being a crocodile was tough, but the water helped keep you warm and fish were dying by the millions, so all you can eat buffet.

        Still, species are resilient and at this point were the genetic product of 4 other mass extinctions, seeds can lie dormant a long time for certain species, animals are amazingly resilient. But either by coincidence, or as a result of an unprecedented impact, or possibly before the impact event (take your pick, lots of debate going around) the mother god of all volcanism started in siberia and lasted for 800,000 years. It released enough lava to cover the entire planet in 20 feet of rock, albeit very slowly. That wasn't really the problem. The problem was all of the carbon and sulfur it released. Amazing quantities of it. Enough to push the temperatures far out of their normal ranges, and create worldwide acid rain. This was the deathknell for most of the species. Plants that were already shocked from the impact had real trouble establishing themselves in rapidly changing climates. Almost every fish that lived in the water column died off (dependant on plankton), only the deep dwelling ones survived. Pretty much every animal that ate exclusively plants or meat died off too. Insectivores and omnivores under about 50 lbs were the only ones who could really find a path to survival (excepting crocs, once again, because they are magic animals with a fantastic niche.) This is where the ability to migrate really shined. Being able to change your habitat was a form of heat regulation, as was burrowing. The earth was, however, pretty close to an all you can eat insect buffet for a long time though, and animal species who were specialized in that arena were able to chart a path through those rapidly changing conditions.

        I've heard a lot of estimates, but the one I believe the most is that after about 5,000 years, species had started to settle into sustainable niche's and the worst of the extinction was done, but in the end 90% of everything living was dead.

        • Re: (Score:2)

          by barakn ( 641218 )

          It wasn't Siberia. The Siberian Traps are 4x older than Chicxulub. You were thinking of the Deccan Traps.

        • Am not disagreeing that an ice-age ensued for long after the K/T event. But I heard a recent RadioLab podcast [wnycstudios.org] with an interesting (new?) perspective.

          The heart of the podcast is a study [pnas.org] which focused on impact-melt spherules that were found in the gills of some Tanis-site riverfish washed ashore by a tidal surge. More correctly: "Acipenseriform fish, densely packed in the deposit, contain ejecta spherules in their gills and were buried by an inland-directed surge that inundated a deeply incised river chan

          • I'll have to listen to the podcast. I saw reporting on the study, Interesting stuff, though surely that level of heat would have chemical effects that would be measurable in the soil of the time. I'll be curious to see what comes out to back up his claims.

        • Also extremely hot, as all the ejecta falling back to earth would have heated up the atmosphere. Most large animals were probably killed in a few days.

  • "But what do the scientists say?" the scientists said.

  • Pics, or it didn't happen. (Score:4, Interesting)

    by DCFusor ( 1763438 ) on Tuesday September 10, 2019 @08:21AM (#59176948) Homepage
    Oh, wait. There are pics of a round earth and people don't believe that.

  • Comment removed (Score:3)

    by account_deleted ( 4530225 ) on Tuesday September 10, 2019 @08:43AM (#59176994)
    Comment removed based on user account deletion
    • I'm also kinda curious as to how much was blasted into space, and to where.

      • I'm also kinda curious as to how much was blasted into space, and to where.

        I suspect some of it achieved Earth escape velocity, which would put it into other orbits and onto the Moon, and eventually onto other planets, moons, and asteroids.

        Of more concern is the much larger amount of material that left the atmosphere but didn't achieve escape velocity. That would end up in suborbital trajectories that would impact the atmosphere all over the planet.

        I've seen descriptions of the result of that. There would

        • Stupid trackpad strikes (the "submit" button again). Recap and continuing:

          Of more concern is the much larger amount of material that left the atmosphere but didn't achieve escape velocity. That would end up in suborbital trajectories that would impact the atmosphere all over the planet.

          I've seen descriptions of the result of that. There would be enough that the whole sky would be glowing in infrared like a broiler oven for hours. That lights fires everywhere that isn't ocean or under heavy snow or ice.

          Wit

          • Also: Even if the sky didn't get broiler-oven hot enough to dry out and ignite all the veggies, you've still got some chunks that are big enough to make it back down, and are VERY hot. So you get a rain of fire-starters all over the planet, too.

            The main differences to outcome are that the fires drying their fuel and spreading takes longer, and the critters have more time to find a hole.

      • I'd imagine a fair amount came raining down over the next couple years.

        I'd be cool if they could link molten rock from this event to some rock found somewhere in Asia. Or even if they could link it to rocks found on the surface of the Moon as I'm sure the Moon plowed right through the debris cloud more than a few times.

        The picture my imagination is creating of this statement is something Michael Bay would droll over: "Rebounding from the hammer blow, a plume of molten rock splashed up into a peak higher th

        • ....

          To bad time travel isn't possible... That'd be a wonder to witness.

          It would be a wonder, if not for the imminent doom. Being near enough to witness the more interesting effects would have been superbly hazardous to one's health. The only safe place to observe would have been from space, but the craft would have had to have been far enough away to not be struck by rock ejected from the impact crater.

      • Ejecta might be categorised in three groups

        1) Below escape velocity - drops back into the atmosphere and lands with a big bang
        2) Close to escape velocity - establishes an elliptical orbit until atmospheric drag brings them down with a bang
        3) Well above escape velocity - leaves the earth-moon system and mostly gets cleaned up by the sun .

        So the vast majority of the debris won't make it out of the atmosphere, and the small fraction which does escape the earth-moon system is unlikely to be in a stable orbital

        • 1) Below escape velocity - drops back into the atmosphere and lands with a big bang

          Big chunks go bang at the end, but all of 'em get vapor-streak hot on the way down. So the sky gets VERY hot for a while. See my post(s) above.

          2) Close to escape velocity - establishes an elliptical orbit until atmospheric drag brings them down with a bang

          Uh-uh. Any closed and unperturbed orbit for such debris intersects the atmosphere (and the planet) at (or near, due to atmospheric drag on the way up) the impact site (ma

          • Fun story: I misread your /. handle as "underground lightning" which piqued my curiosity and I went googling for it and found this page titled Underground Lightning Discharges [bibliotecapleyades.net]. Learned about Telluric current [wikipedia.org] flowing through the Earth. Apparently can be used in prospecting for water among other things, which got me thinking about dousing rods [borderlandsciences.org] and the connection there. Then came back here and realized I misread your handle. :)

          • 1) Below escape velocity - drops back into the atmosphere and lands with a big bang

            Big chunks go bang at the end, but all of 'em get vapor-streak hot on the way down. So the sky gets VERY hot for a while. See my post(s) above.

            Intuitively, given the velocities involved, they are going to be vapor-streak hot on both the way up and down. The ejecta would rain across a huge westerly swath as the Earth rotated underneath it.

            That could never happen again, right? How's that Mars colony going again? :(

      • If any went into space over the millions of years, most of it has fallen back to earth. For small light particles it is difficult for it keep a stable orbit for millions of years. We have satellites that fall back to earth which are launched with mathematical precision into orbit. But we have things like our big moon, and the sun ever so slightly nudging debris out of orbit.

    • Re: (Score:2)

      by dargaud ( 518470 )
      Deccan Trap [wikipedia.org] are thought by many to have formed on the other side of the impact point from the violent echo that concentrated there are broke the crust into pieces. An interesting read. If I had a time machine I would go and watch that day from a safe distance...

      • That's a possibility, but if so, you would expect other examples, from far larger impacts than Chicxulub. And the Deccan traps are essentially unique. Chicxulub was a pretty big hit, but not remotely the biggest, so, where are the other traps or evidence of similar effect? They may have been subducted since, but hard to imagine they all have.

      • Confucius say, "To witness great events is often a misfortune". Well, Confucius or Benjamin Franklin, one of those two.

        Apparently the Traps were around before the impact, but the impact caused 70% of the magma eruptions. At least, so it is hypotenused.

        • Apparently the Traps were around before the impact

          Traps have been around that long? I thought it was a relatively recent anime thing.

  • This is the stuff I come here for!

  • It's the iridium anomaly.
    https://en.wikipedia.org/wiki/... [wikipedia.org]

  • The dinosaurs were not entirely wiped by this extinction event. Most died out, true, but some survived and became birds.

  • "The asteroid blasted a cavity between 25 and 30 miles deep in the first seconds of impact, creating a boiling cauldron of molten rocks and super-heated steam, according to the scientists' interpretation of the rock."

    "as the immense asteroid blasted a hole 100 miles wide and 12 miles deep, the scientists said."

    Someone is confused, possibly the scientists, though more likely the WSJ reporter or me.

    Also, i don't think we're 100% sure that it was "the single worst day in the history of life on Earth". Th

  • At first they say 12 mile deep hole, than 25 mile deep hole. Its mind scrambler to use constantly conflicting figures like this.

  • Delicious!

    Slightly surprised I haven't seen anyone bitch about "city sized" and ask what city, what measurement system, etc etc. Cool article, though.

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