We now want to talk about the Cretaceous extinction event. The Cretaceous extinction is the last of those big five extinction events that we mentioned, and there's a good chance you're going to be responsible for knowing about it, and it's also one that there's a good chance you already know at least something about. So this one happened about 66,000,000 years ago, and it killed the dinosaurs. Alright? And we want to say we also sometimes refer to it as the KT extinction event.
So, just if you see KT extinction, that's what we're talking about. That k, that's just how you spell Cretaceous in German, and the t comes from the tertiary, which comes after this. Alright. So what was life like at this time? Well, there were dinosaurs.
Now it says we had dinosaurs. Right? So after this, the dinosaurs are gone. But at this time, there were T-Rex and Velociraptors running around. Now there are flowering plants.
Flowering plants really diversified during the Cretaceous. There were mammals. A lot of people don't realize this, but there were actually a lot of mammals at this time, probably hundreds of species. Now a lot of them go extinct, but most of the mammals at this time were small. Really all the mammals were small, probably raccoon size and mostly smaller than that.
Now we have lots of insects and specifically bees and ants, the social insects have evolved at this time. Alright. So what happens was this Cretaceous extinction event, we're going to say wipes out about 75% of all species, and most notably those non-avian dinosaurs. Alright. What do we mean by non-avian?
Well, avian refers to birds. So you may realize that birds or you may know that birds are descended from dinosaurs. So one way to think about it is birds are the only dinosaurs that didn't go extinct. Now to be clear, there were a lot of birds alive at this time, and most of them went extinct. But the few species that didn't, they survived and they, you know, evolved into all the species of birds that we see today.
Alright. Well, what happened? We call this the impact hypothesis. My own personal name for it is just a very, very bad day on planet Earth. Alright.
So what happened was a meteorite struck Earth near the Yucatan Peninsula in the Gulf of Mexico. Right? This meteorite was like 10 kilometers wide, over 6 miles wide, and it slammed into Earth with what we think is about the energy of a 1,000,000,000 atomic bombs. So imagine, right, here's our image. We have basically, like, a 1,000,000,000 atomic bombs going off in the Gulf of Mexico there.
What's going to happen? Well, first off, we get these mega tsunamis. Right? These tidal waves that wash deep inland on different continents. Well, we're also going to have worldwide firestorms.
So right. Basically, the forests all over Earth are going to catch fire as well. All the debris that gets kicked up, it starts raining down all over the planet, basically as fireballs. And how big these firestorms were is a little bit debatable, but some people think basically all forests on earth caught fire that day. Alright.
So that's relatively short term. We're talking about, you know, the hours and days after this impact. Now as we go a little bit long term, we're going to go into a global winter. Right? From all the debris that has been kicked up, it sort of hangs out in the atmosphere.
We think for about 3 years, blocking out the sun, and well, for 3 years, we have winter on Earth. That can be tough to survive if all of a sudden without warning, you go into 3 years of winter. Now after those 3 years and up to that, debris comes down, and it goes back to a little bit normal. But we have this horrible acid rain and ocean acidification. Alright.
Acid rain and ocean acidification. The acid rain is going to kill all sorts of plants, the things that eat plants. Ocean acidification makes it hard for all sorts of different organisms to survive. And from all the stuff that's kicked up and from all the burning, etcetera, we think that we get about a 100,000 years of global warming after this. Right?
So after this, we get a 100,000 years of major climate change. Alright. All that together, it's tough to survive. Right? So why did the mammals survive?
Well, again, most mammals went extinct. Right? Only maybe two dozen species of mammals survived. We think they were small, and they were generalists. They were able to eat all sorts of different food sources, so they weren't reliant on one thing that died off.
You know, they could eat seeds, scavenge other dead things, and survive that really bad day, those really bad sort of couple years after this. Now we just do want to note that other factors, specifically volcanic activity, may have contributed to this extinction event. Some people think that this extinction event was a bit of a longer extinction event with all this sort of global volcanic activity going on, and this impact sort of punctuated it and knocked a lot of things out sort of right in the middle. Alright. Well, with that, we're going to look at this more in examples and practice problems.
There will be more death and destruction to come. See you there.