This New Evidence Could Rewrite the Dinosaur Extinction | Astrum Earth

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Why do we think a single asteroid ended the dinosaurs?

James Stewart 0:00
Sixty-six million years ago, a city-sized asteroid slammed into Earth, ending the reign of the dinosaurs. The largest creatures ever to have walked the planet gone, just like that. It's a story we're all familiar with. One asteroid cataclysmic impact results mass extinction. Case closed. Right? Well what have I told you we've been telling this tale all wrong? New discoveries on the ground, scientific breakthroughs, and cutting-edge technology are revolutionizing our understanding of the events from that fateful day. And it turns out there's much more to it than we thought. When the asteroid hit, was Earth already a planet in crisis? Did another catastrophic event add to the terror? Um were there any survivors after all?
James Stewart 0:57
I'm James Stewart, and you're watching Astrum Earth. Join me today as we travel back in time to investigate what really killed the dinosaurs. We'll take stock of all the evidence to bring you the ultimate guide to their downfall. But be warned, science might not tell you the tale you're used to. We modern humans have existed for a reasonably long time, around 300,000 years. But on evolutionary timescales, that really is well, nothing. Dinosaurs walked the Earth for some 180 million years, completely dominating the land for 160 million of them. That's 500 times longer than we've been here. They really did seem unstoppable. Yet, 66 million years ago, somewhere in the darkness of space, an object was on its way that had the power to wipe them out.
James Stewart 1:54
We've known the broad outline of this story for decades, but scientists are still piecing together the evidence to work out exactly what happened on that fateful day, and the closer they look, the more complicated the narrative gets. There are holes in the story, clues that simply don't add up, and it's planted seeds of doubt. Could one simple asteroid truly have wiped out the largest beasts ever to walk the Earth? If we want to tell a story of ancient Earth, the best place to find it is in the ground itself. Every sediment layer acts like a different chapter in the tale. And locked within the rocks of every continent is one page, I mean, quite literally, a thin layer of sediment that marks the boundary between two worlds.
James Stewart 2:44
Above the line, a new world begins. Below it is the lost world of the dark.

What is the Cretaceous‑Paleogene (K‑Pg) boundary and why does it matter?

James Stewart 2:50
Dinosaurs. This mysterious dark grey band of sediment circles the entire globe. A record that's been preserved for millions of years. It's called the Cretaceous Paleogene Boundary, or KPG boundary for short, and was discovered back in 1979 by a father and son geologist duo, Louis and Walter Alvarez, who were just out collecting rocks in an Italian gorge. What they found inside this lair would change our understanding of Earth's history and of extinction events forever, because the lair was curiously enriched with unusually high levels of iridium, a metal usually vanishingly rare in Earth's crust. So how did all that iridium get here? Well that, I suspect, you already know the answer to. Iridium is very common in meteorites and comets, and the discovery of this lair was the smoking gun linking a giant asteroid to the mass extinction that ended the age of the dinosaurs.
James Stewart 3:54
And this wasn't just any old asteroid. This one was the size of a city, travelling at 72,000 kilometers per hour faster than a bullet. It slammed into what is now the Yucatán Peninsula in Mexico. The impact unleashed more energy than humanity's entire nuclear arsenal combined. As you can imagine, that certainly left its mark. Hidden beneath layers of rock and sediment lies a colossal crater nearly 200km wide and 20km deep. For 66 million years it remained buried and forgotten. And then in 1991, geologists searching for oil accidentally stumbled across it. Named the Chicksalube Crater and nicknamed Crater of Doom, it is one of the most important geological discoveries ever made. Not because of its size, but because of what it contains.
James Stewart 4:51
Every stage of this catastrophic asteroid impact left a physical signature in the rock layers. It's like a time capsule we can peer inside of.

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