Life bounced back after the dinosaurs died Kirk Johnson at work at the Bowring Pit in the Denver Basin, where his research team studied the sedimentary rock site. (Rick Wicker/iStock/estt)
Life bounced back after the dinosaurs died
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A six mile-wide asteroid struck the Earth 66 million years ago. It was one of the worst days in the history of the planet. About 75 percent of the known species were rapidly driven to extinction. These included the non-avian dinosaurs like Tyrannosaurus, the flying pterosaurs and the coil-shelled squid cousins called ammonites. And there were many more.
 
Life was not totally extinguished, however. The close of the Age of Dinosaurs opened up the path to the Age of Mammals. Now a new study has been done. It helps put a timer on how quickly life bounced back.
 
A new Earth and Planetary Science Letters paper has been produced. Smithsonian's Kirk Johnson, director of the National Museum of Natural History, geologist William Clyde of the University of New Hampshire and their coauthors draw from the fossil and rock record of the Denver Basin. They try to determine what happened after the devastating asteroid impact. The region is located in eastern Colorado. It extends into Wyoming and Nebraska. The region is one of the best places in the world to examine the change.
 
"The Denver Basin was actively subsiding. And the adjacent Colorado Front Range was actively uplifting during the last four million years of the Paleocene," Johnson says. It means, "the basin was acting like a tape recorder of local events." Better still, he says, nearby volcanic eruptions spewed plenty of ash. It was enough that geologists now have hundreds of layers that can be given absolute dates to determine the age of these rocks.
 
These rocks provide a more precise timing for what's seen in the fossil record.
 
The change between the Late Cretaceous and the subsequent Paleogene period is stark.
 
"The Late Cretaceous was forested and warm," Johnson says. Forests were dominated by broadleaf trees, palms and relatives of ginger. Then the extinction struck. It stripped away the big herbivorous dinosaurs. And, says paleobotanist Ian Miller of the Denver Museum of Nature & Science, it killed about 50 percent of plant species. The surviving species created a new landscape.
 
"Within two million years of the impact, the Denver Basin had the world's first known tropical rainforests and mammals of medium body size," says Johnson.
 
The study focuses on what happened between those points. Using a technique known as uranium-lead dating, the geologists determined that the K/Pg boundary (the layer that records the asteroid strike and marks the divide between the Cretaceous and subsequent Paleogene period) was 66.021 million years ago.
 
Johnson and colleagues estimate that the time between the last known non-avian dinosaurs and the earliest Cenozoic mammal was about 185,000 years. They say it was no more than 570,000 years. That's just a blip from the perspective of Deep Time. That's the incomprehensible span of ages. It is where the whole of human history is just a footnote.
 
The landscape during this transition didn't resemble the Cretaceous forests or the sweltering rainforests that came after. Fossil pollen records show that there was what paleontologists refer to as a "fern spike." It was when these low-growing plants proliferated over the landscape. It lasted about 1,000 years. That's because ferns thrive after disturbances, Miller says. "They just need a little bit of substrate and water and they are off."
 
The dates and fossils speak to how dramatically the extinction changed the planet. Not only was the mass extinction extremely rapid, but life recovered relatively quickly as well. There was less than half a million years between the likes of Triceratops and the time when the surviving mammals started to take over the basin's recovering ecosystems.
 
"The new paper really drives home the point that the extinction was, from a geological standpoint, immediate, catastrophic and widespread," Miller says.
 
Studies like these are offering ever-greater resolution of scenes from the deep past.
 
"Geochronology is getter better and more precise all the time. And this study applies it to a unique outcrop that is unparalleled in its ash bed sequence," Johnson says. He adds that studying such patterns isn't just ancient history. "The K/Pg was both instant and global. So it is a very interesting analogy for the industrial Anthropocene of the last century," Johnson says.
 
By studying the past, we may catch a glimpse of the future we're creating.

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CRITICAL THINKING QUESTION
How do we know that a six mile-wide asteroid struck the Earth 66 million years ago?
Write your answers in the comments section below


COMMENTS (91)
  • tylers531-stu
    10/03/2016 - 02:52 p.m.

    i think that this is cool because i like dionsours they are cool and they look cool

  • kodyz-stu
    10/03/2016 - 02:52 p.m.

    Because how else woud 75% of species die out.

  • holdenj-orv
    10/03/2016 - 02:54 p.m.

    This Is One Of The Biggest Explosions Known In History. The Biggest Explosions In History From Smallest to Biggest{Sort Of}:Random Explosion in Siberia; 1908, the Port Halifax, Canada Disaster of; 1917, the Port Chicago Disaster; 1944, The Atomic Bombings of Hiroshima/Nagasaki; 1945, This, And Finally The Soviet Tsar Bomba Test; 1961. Note: The Tsar Bomba Was A 50 Megaton Soviet Hydrogen Bomb Tested in the Arctic Circle.

  • samj-stu
    10/03/2016 - 05:35 p.m.

    Scientist found out about the creater and it's size and with that informatio they found a bit about the length. I think that the impact must have caused alot of air polluted to have killed 70% living thing back then.

  • brooklynb-stu
    10/03/2016 - 05:51 p.m.

    maybe they found out that the six mile-wide asteroid stuck the Earth 66,000,000 years ago, because now scienticts are able to tell the age of rocks such as asteroids or medeore. Maybe they found the asteroid and did a little reserch on it and found out that it was 66,000,000 years ago.

  • calebs1-stu
    10/03/2016 - 08:34 p.m.

    I was superized that it only took up to 570,000 years for more animals to take over. I thought mor like a couple million years.

    • evanl-stu
      10/04/2016 - 08:30 a.m.

      i find it facininaitng that some people find the craters and are able to get things out of there from ht e dinosaur ages

  • anag-stu
    10/04/2016 - 08:01 a.m.

    im kinda lost but is a really good book because it telling me about how dinoaurs were on earth

  • mikalr-stu
    10/04/2016 - 08:07 a.m.

    we dont know that a astroid struke thats what we think and we have kinda found proof from searching the Earth.

  • samp1-stu
    10/04/2016 - 08:32 a.m.

    It ia amazing that there is an asteroid that big. The cool thing is that we can find the animals that die because of the asteroid.

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