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Asteroid impact, not volcanic activity, killed the dinosaurs, study finds

This artist's visualization shows an Ankylosaurus magniventris, a large armored dinosaur, witnessing an asteroid impact 66 million years ago. (Image credit: Fabio Manucci)

An asteroid impact, not volcanic activity, killed the dinosaurs, a new study finds. 

For decades, scientists have gone back and forth over exactly what caused a mass extinction event 66 million years ago, which destroyed about 75% of all life on Earth, including all of the large dinosaurs. Some have thought that volcanic activity could be to blame, but one new study shows that a giant asteroid impact was the prime culprit.

Scientists have known that the impact, which created the massive Chicxulub impact crater (located in what is now the Yucatán Peninsula in southeast Mexico), was a major contributing factor to this extinction event. But volcanic activity happening at around the same time has raised questions over which could have been the main factor which changed conditions on our planet that led to the demise of Earth's creatures.

In a new study, researchers from Imperial College London, the University of Bristol and University College London have shown that the asteroid impact, not volcanic activity, was the main reason that about 75% of life on Earth perished at that time, and it did so by significantly interfering with Earth's climate and ecosystems. 

"We show that the asteroid caused an impact winter for decades, and that these environmental effects decimated suitable environments for dinosaurs. In contrast, the effects of the intense volcanic eruptions were not strong enough to substantially disrupt global ecosystems," lead researcher Alessandro Chiarenza, who conducted this work whilst studying for his PhD in the Department of Earth Science and Engineering at Imperial, said in a statement. "Impact winter" signifies a semi-permanent "winter" created when sunlight-blocking particles are kicked up into the atmosphere after an impact. "Our study confirms, for the first time quantitatively, that the only plausible explanation for the extinction is the impact winter that eradicated dinosaur habitats worldwide."

To come to this conclusion, the researchers modeled how Earth's climate would be expected to respond to two separate possible extinction causes: volcanism and asteroid impact. In these mathematical models, they included environmental factors including rainfall and temperature, which would have been critical to the survival of these species. They also included the presence of sunlight-blocking gases and particles and carbon dioxide, a greenhouse gas

"Instead of only using the geologic record to model the effect on climate that the asteroid or volcanism might have caused worldwide, we pushed this approach a step forward, adding an ecological dimension to the study to reveal how these climatic fluctuations severely affected ecosystems," co-lead author Alex Farnsworth, a climatologist at the University of Bristol, added in the same statement. 

With these models, the team found that the giant asteroid hitting our planet would have released tremendous amounts of gas and particles into Earth's atmosphere, blocking out the sun for years on end. This effect would have created a sort of semi-permanent winter on Earth, making the planet unlivable for most of its inhabitants.

Now, while the team found the asteroid impact to be the major factor in making Earth unlivable for most animals, they also found that volcanic activity could have actually helped life to recover over time, a conclusion that scientists have drawn before

They found that, while volcanoes do release sunlight-blocking gases and particles, which would have helped to block the sun in the short term, they also release large amounts of carbon dioxide which, because it's a greenhouse gas, would have built up in the atmosphere and warmed the planet. 

So, as the researchers suggest in this work, while the devastating winter caused by the asteroid killed off most life on Earth, over time, the warming effect created from the volcanic greenhouse gases could have helped to restore life to habitats. 

"We provide new evidence to suggest that the volcanic eruptions happening around the same time might have reduced the effects on the environment caused by the impact, particularly in quickening the rise of temperatures after the impact winter. This volcanic-induced warming helped boost the survival and recovery of the animals and plants that made through the extinction, with many groups expanding in its immediate aftermath, including birds and mammals," Chiarenza added. 

This work was published June 29 in the journal Proceedings of the National Academy of Sciences.

Email Chelsea Gohd at cgohd@space.com or follow her on Twitter @chelsea_gohd. Follow us on Twitter @Spacedotcom and on Facebook.

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  • Helio
    I vaguely recall seeing that the time frame for this volcanic hypothesis was found wanting as well.
    Reply
  • sciguybm
    That's the funny thing about trying to hypothesize about the past; who knows? Why: no one knows.
    So let's try this one for size; asteroid, volcanoes cool the earth, not much, a few degrees. The impact crater isn't large enough to cause an extinction event.
    In the cooling, a new enemy emerges: mammals. At night they roam the planet growing larger as they feed on dinosaur eggs by the trillions... mama dino too stiff to defend the nest.
    So how come some dinosaurs survived? Look at their nesting habits and figure it out.
    But OH NO; we CAN'T blame the mammals because then it is one one small step to blaming the humans for this extinction event happening today.
    Besides, I offer for proof that many dinosaurs had already become extinct before this event and many survived this event by millions of years.
    To think: someone actually pays the lizard brains who wrote and collaborated on this junk.
    Reply
  • slingledude
    Really? 66 million years? Just how do they come up with that number!? Besides, the world has been in existence for just about 6,000 years.
    Reply
  • COLGeek
    slingledude said:
    Really? 66 million years? Just how do they come up with that number!? Besides, the world has been in existence for just about 6,000 years.
    What is the 6000 years based on?
    Reply
  • capetonian
    slingledude said:
    Really? 66 million years? Just how do they come up with that number!? Besides, the world has been in existence for just about 6,000 years.
    Are you being funny, or <<edited by moderator>>...?
    Reply
  • dfjchem721
    slingledude said:
    Really? 66 million years? Just how do they come up with that number!? Besides, the world has been in existence for just about 6,000 years.

    The date was established by the argon-argon technique*. It is very precise and is now widely accepted by most in the the dating sciences.**


    * https://phys.org/news/2013-02-precise-dates-comet-asteroid-impact.html

    ** https://en.wikipedia.org/wiki/Argon-argon_dating

    One of the most important and accurate dating techniques, when appropriate, is established by U-238 decay***, the gold standard for "long" events. U-238 decay has specific daughter elements that must arise from the parent decay.

    Since the daughter elements have only one source, the decay can be accurately established based on the half life of U-238 (4.5 billion years). Of course the objects being analyzed must not have this decay "clock" reset by melts, etc. That is why zircon crystals are used in many cases for really ancient events.

    And there were relatively advanced civilizations in the middle east well over 6,000 years ago. Carbon dating (C14 decay) is good for those artifacts.


    *** https://en.wikipedia.org/wiki/Uranium–lead_dating
    And there is nothing wrong with being funny, well, sometimes maybe there is........
    Reply
  • PatB
    Admin said:
    An asteroid impact, not volcanic activity, killed the dinosaurs, a new study finds.

    Asteroid impact, not volcanic activity, killed the dinosaurs, study finds : Read more
    An asteroid impact 66 million years ago. Woah! What if those incredible dinosaures were part of an incredible machination of the Establishment, one amid many others.
    Reply
  • Grthinker
    This is SO OLD NEWS!!!. We've known about that crater off the north shore of South American for .... at least a decade.
    Reply
  • YetAnotherBob
    sciguybm said:
    That's the funny thing about trying to hypothesize about the past; who knows? Why: no one knows.
    So let's try this one for size; asteroid, volcanoes cool the earth, not much, a few degrees. The impact crater isn't large enough to cause an extinction event.
    In the cooling, a new enemy emerges: mammals. At night they roam the planet growing larger as they feed on dinosaur eggs by the trillions... mama dino too stiff to defend the nest.
    So how come some dinosaurs survived? Look at their nesting habits and figure it out.
    But OH NO; we CAN'T blame the mammals because then it is one one small step to blaming the humans for this extinction event happening today.
    Besides, I offer for proof that many dinosaurs had already become extinct before this event and many survived this event by millions of years.
    To think: someone actually pays the lizard brains who wrote and collaborated on this junk.

    One problem here for your idea is that mammals are as old as the dinosaurs. Yes, there were mice/rats/opossums and so forth all through the 'time of the dinosaurs'. we generally only find the teeth, but rodent teeth are there in abundance.

    You have to then come up with a reason why after two hundred million years of never being a threat, suddenly there is a mammalian uprising. but there are other problems for your explanation as well. Why was it that so many tree species or fish species in the oceans vanished at precisely the same time, planet-wide? Were there rat scuba divers with bombs?
    What the Article does is to document the resistance of the gradualist school of Darwinists to the idea of external catastrophe playing any role in the history of life. To put it flatly, the Darwinist adherence to their religion is against the science.
    Catastrophe's happen.
    To make matters worse, some planetary physicists have maintained that the large burst of volcanism afterwards was a result of the asteroid strike.
    Reply
  • Wally Mayo
    YetAnotherBob said:
    One problem here for your idea is that mammals are as old as the dinosaurs. Yes, there were mice/rats/opossums and so forth all through the 'time of the dinosaurs'. we generally only find the teeth, but rodent teeth are there in abundance.

    You have to then come up with a reason why after two hundred million years of never being a threat, suddenly there is a mammalian uprising. but there are other problems for your explanation as well. Why was it that so many tree species or fish species in the oceans vanished at precisely the same time, planet-wide? Were there rat scuba divers with bombs?
    What the Article does is to document the resistance of the gradualist school of Darwinists to the idea of external catastrophe playing any role in the history of life. To put it flatly, the Darwinist adherence to their religion is against the science.
    Catastrophe's happen.
    To make matters worse, some planetary physicists have maintained that the large burst of volcanism afterwards was a result of the asteroid strike.
    Good response. Many people do not realize how detailed our knowledge is regarding geological/planetary history, including early faint sun, Theia collision, lack of oxygen until two main oxygenation events, five supercontinent episodes, 5-7 main near extinctions, one with near 95% of land and 70% of marine creatures.
    The near extinctions do fly in the face of any old-style evolutionary picture of a nice steady and quiet methodical progression of creatures.
    But, focusing on this article, it is well-known that severe asteroid events can cause a huge response in large scale volcanic activity, some so violent that enough magma in one episode of Siberian volcanes was enough to equivalently pave the surface of the earth 12-20' deep. This has happened more than once. So, while the impact alone could be sufficient, vulcanism alone could, too. So, it's hard to pull that apart, and really know which did the most damage.
    It's not all as the public perceives. On dinosaurs, I have fun asking my science students which came first, ants or dinosaurs? The surprise answer is dinosaurs (though some other "insects" predate).
    Reply