The K-Pg Extinction Event
Describe the Cretaceous–Palaeogene (K-Pg) extinction event approximately 66 million years ago, including the asteroid impact theory and its evidence (iridium layer, Chicxulub crater), and understand that this ended the reign of non-avian dinosaurs
What a learner can do afterwards
- State that the K-Pg extinction happened about 66 million years ago and wiped out non-avian dinosaurs
- Describe the asteroid impact hypothesis and name the Chicxulub crater in Mexico
- Explain one piece of evidence: the iridium-rich layer found worldwide in rocks from that time
The lesson
About 66 million years ago, something terrible happened to Earth. Almost all the dinosaurs from the Mesozoic Era died out. Only their bird relatives lived on. Scientists call this the K-Pg extinction, and they have worked hard to figure out what caused it.
The leading idea is that a huge asteroid, a giant rock from space, slammed into Earth. It hit near what is now the coast of Mexico, punching out a crater called the Chicxulub crater. Most of the crater is now buried under ground and ocean, but it stretches for dozens of miles.
Around the world, geologists dig through rock layers and find a thin, strange band. It is unusually rich in a metal called iridium. Iridium is rare in Earth's crust but common in asteroids. Finding this iridium layer everywhere, right at the same rock age as the extinction, is strong evidence that something from space struck Earth.
Remember, not all dinosaurs vanished. Birds are a group of dinosaurs, and their ancestors survived the extinction. In a way, dinosaurs are still around today, flying above your head.
A giant asteroid struck Earth about 66 million years ago, and the worldwide iridium layer in rocks is key evidence for that impact.
Watch it
Where it sits
Where this leads
Jobs that lean on this skill. Follow one to see everything it is built on.
8 questions wait behind this lesson, each with its answer explained. Every answer feeds the sky: stars light as they are learned, and dim when it is time to come back.