---
title: "The K-Pg Extinction Event"
description: "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 t"
canonical: https://lightmysky.com/learn/science/the-k-pg-extinction-event-mt_QHKqckBdAk
source: https://lightmysky.com/learn/science/the-k-pg-extinction-event-mt_QHKqckBdAk.md
retrieved: 2026-10-19
---

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# 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

Subject: Science · Area: Dinosaurs & Paleontology · Ages 9 to 11
Page: https://lightmysky.com/learn/science/the-k-pg-extinction-event-mt_QHKqckBdAk

## Ready when they can

- 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

## Lesson: The K-Pg Extinction: How the Dinosaurs' Reign Ended

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.

*(drawing: The asteroid strike set off a chain reaction that changed life on Earth.)*

**Example.** 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.

**Tip.** 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.

**Recap.** A giant asteroid struck Earth about 66 million years ago, and the worldwide iridium layer in rocks is key evidence for that impact.

## Practice

8 questions on this page, each with its working shown.

## Needs first

- [Dinosaurs Were Real](https://lightmysky.com/learn/science/dinosaurs-were-real-mt_dpM1l5IOk6)
- [The Mesozoic Era](https://lightmysky.com/learn/science/the-mesozoic-era-mt_uQljqc0J5j)

## Opens up

- [Changing Scientific Knowledge](https://lightmysky.com/learn/science/changing-scientific-knowledge-mt_0T0Zf0YG6k)
- [Mass Extinctions in Earth History](https://lightmysky.com/learn/science/mass-extinctions-in-earth-history-mt_IP0PTVfTXp)