End of Tyrannosaurus rex
A Layer of Airfall from the Chicxulub Impact

One of the greatest calamities to happen in the last several hundred million years ago happened 66.043 million years ago when an asteroid, about the size of Manhattan Island, slammed into a shallow sea that then covered what is now the northern edge of the Yucatan Peninsula. Giant sea waves were formed. Debris churned up by these giant waves can be seen in road cuts along State Highway 24 east of Montgomery, Alabama, that connects the small towns of Moscow Landing and Mussel Creek. There was also a tremendous amount of material that was thrown up into the air. Some of it was ejected into space. Other parts fell as huge stones close to where a giant impact crater formed. And some of it was pulverized and injected high  into the atmosphere where winds caught it and swept it around the Earth. This pulverized debris eventually fell out of the sky. One of the places where a layer of this airfall debris can still be found (and is easily accessible) is at Trinidad State Park in Colorado.

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A thin layer of airfall debris lies beneath a brown, massive sandstone.

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At Trinidad, the layer is of white clay that is half-an-inch thick. The US quarter is for scale.

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A close-up of the white clay layer, material that fell out of the air after the impact.

The impact produced a 120-mile-wide crater on the Yucatan Peninsula. The crater is now buried by later marine sediments. The impact greatly disturbed and weakened sections of the surrounding crust. As a result, an arc of incredibly beautiful sinkholes have formed. Known as cenotes, these sinkholes formed where acidic rainwater has seeped into the underlying limestone, undermining the rock and causing it to collapse and exposing pools of groundwater underneath.

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Cenote Holatun (Photo by James Balog)

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Cenote Samuel (Photo by Dennis Sylvester Hurd)

But were the effects of the Chicxulub impact so severe that it caused the mass extinction at the end of the Cretaceous Period and the end of the dinosaurs?  Probably not.

The asteroid approached the Earth from the south and hit the Earth at the Yucatan Peninsula. As a result, the most devastating effects were to the north across North America. It was on North America that Tyrannosaurus rex lived, and so it probably did become extinct as a result of the impact. But the effects of the impact were less severe elsewhere on the planet. But another catastrophic global event happened soon after: the eruption of vast volumes of lava as the Deccan Traps.

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Tyrannosaurus rex (Photo by David Monniaux)

The Deccan Traps are in India. And the eruption of those lavas begin a hundred thousand years or so before the Chicxulub impact.  BUT the main phase of the eruption occurred within a ten thousand years or so after the Chicxulub impact. The eruption emitted large amounts of smoke and huge volumes of carbon dioxide. It was the eruption of the Deccan Traps that probably led to the mass extinction at the end of the Cretaceous. But did the Chicxulub impact have a role? Yes.

The Chicxulub impact and the Deccan Traps are the largest meteor impact and the largest volcanic eruption of the last hundred million years. And they occurred within about ten thousand years of each other, the eruption following the impact. And so the impact—in some way that is still debate—may have triggered the main phase of the Deccan Traps.

As devastating as the end-of-the-Cretaceous extinction was to animal life on the planet, some forms show no significant effects, such as lizards, frogs, salamanders, crocodiles, alligators and turtles. And some dinosaurs did survive. Their descendants are today's birds.*

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*A vast variety of birds existed during the Cretaceous, including birds with teeth. But only about five groups of birds survived the end-of-the-Cretaceous extinction, birds that were similar to today's ducks, chickens and quail. All of today's birds, which number more than a ten thousand species, are descended from those few survivors.