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  • One of the hottest controversies in science is all about what happened sixty-six million years ago

  • when dinosaurs were snuffed out of existence.

  • It's been told that an asteroid more than 10-kilometers across slammed into the Yucatan Peninsula,

  • putting an end to the dinosaur's long reign.

  • But the actual 'cause of death' has been the center of a decades-long raging controversy.

  • Many scientists have argued for alternative theories to explain what brought on the dinosaur's final days,

  • including cosmic rays, an outbreak of disease, or as we previously reported,

  • an inferno of blazing wildfires.

  • But thanks to this recently published study in Science,

  • we may have finally learned the truth behind what killed them.

  • Aside from the asteroid, there is another competing theory involving massive volcanic eruptions

  • that happened around the same time,

  • leading to some confusion over which is the actual culprit.

  • Over 500,000 cubic kilometers of lava welled up from the ground

  • and spread across much of what is now India

  • a volume larger than twenty times all of the Great Lakes combined.

  • This created enormous deposits of igneous rock, now known as the Deccan Traps.

  • Along with the lava, the eruptions released carbon dioxide and other gases into the atmosphere,

  • driving global temperature changes thought by some

  • to have contributed to the extinction of ¾ of the world's species at the end of the Cretaceous period.

  • Vital clues to answering this prehistoric puzzle were found in sediment cores,

  • like the ones collected in 2012 by the research vessel JOIDES Resolution,

  • as part of the International Ocean Discovery Program (IODP).

  • The cores may not have looked like much,

  • but combined they held more than 40 million years of ancient climate history,

  • including a band of rock known as the K-T or K/Pg Boundary,

  • which clearly shows the impact of the asteroid.

  • On one side of the boundary we find the Cretaceous period,

  • where dinosaurs were busy living large.

  • On the other, we find the Paleogene, where poof

  • the dinosaur party had come to an abrupt end.

  • Despite this, “Team Volcanohas argued that all four prior mass extinctions

  • can also be explained by volcanic activity.

  • And that asteroids have pummeled the planet before and life kept on moving.

  • In 2019, researchers were finally able to use the deep-sea sediment cores

  • collected from the 2012 expedition to settle the argument.

  • They modeled several scenarios, varying the timings of the Deccan Traps eruptions

  • to see how the gases might have affected the climate.

  • They compared the modeled temperature changes to the global temperature data recorded in the cores

  • to see if any of these scenarios lined-up with the mass extinction better than the asteroid impact.

  • In one of the hypothetical scenarios,

  • researchers placed the bulk of the eruptions a couple hundred thousand years before the K/Pg boundary.

  • This model lined-up with a temporary 2 degree rise in the temperature record,

  • but since the temperature returned to normal before the asteroid impact,

  • the Deccan Traps eruptions did not coincide with the extinction.

  • In the second scenario, the eruptions were split evenly before and after the asteroid impact,

  • but the volcanic disruptions that took place after the K/Pg boundary didn't significantly alter the climate,

  • which wasstrange.

  • Researchers found that a lack of global warming after a major burp of carbon dioxide

  • could be explained by the extinction of tiny single-celled marine creatures called foraminifera or forams.

  • In a process called the carbon cycle,

  • the ocean dissolves carbon dioxide from the atmosphere,

  • where forams capture the carbon from it to build their shells.

  • When forams die, they sink, and the carbon trapped in their shells is deposited on the ocean floor,

  • moving it along to the next stage in the carbon cycle.

  • But after the K/Pg boundary, the forams are nearly wiped out of existence.

  • Without forams to move carbon, the oceans may have absorbed large amounts of volcanic carbon dioxide,

  • limiting its effect on climate.

  • This new research produced a definitive timeline that likely ends the decades-old argument

  • that was often as heated as the volcanos themselves.

  • It also establishes that the Deccan Traps eruptions alone could not have caused the extinction,

  • proving it was the impact that wiped out the dinos.

  • Other extinctions seem to have happened over hundreds of thousands of years,

  • but what happened at the K/Pg boundary looks like it took just a few hundred.

  • Regardless of whether we're talking about volcanos or asteroids,

  • both fill the air with carbon dioxide, ash, and noxious gases,

  • just like humans are doing now by burning fossil fuels.

  • Someday, a newly-reigning species could be examining fossils of us.

  • That's why getting a detailed picture of extinctions past with research like this is so important...

  • to get to the CORE of the matter of life and death on Earth.

  • Dinos may have not survived the K/Pg event, but you know what did?

  • The Wonderchicken!

  • Learn more about it check out this episode here.

  • And if you have any prehistoric science you want us to cover, let us know down in the comments.

  • Make sure to subscribe to Seeker and thanks so much for watching.

One of the hottest controversies in science is all about what happened sixty-six million years ago

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What Really Killed the Dinosaurs?

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    Summer に公開 2020 年 10 月 08 日
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