---
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: 2026-11-12
---

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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, at the end of the Cretaceous period, all non-avian dinosaurs died out. Non-avian means not birds. Some birds survived, and birds are dinosaurs alive today. This was part of the K-Pg mass extinction, when many kinds of plants and animals died out. K-Pg names the boundary between the Cretaceous and the following Palaeogene period.

A huge asteroid, a rock from space, struck Earth near what is now Mexico's Yucatan Peninsula. The impact formed Chicxulub crater, which is mostly buried beneath land and sea. The crater and rocks from that time provide evidence that the impact was a major cause of the K-Pg extinction.

*(drawing: Dust and soot reduced sunlight. This chain shows how food became scarce, not that every plant or animal died.)*

**Example.** A thin layer in rocks from the time of the extinction is rich in iridium. Scientists have found this layer in many parts of the world. Iridium is rare in Earth's crust, but many asteroids contain much more of it. The layer's age and wide spread, together with Chicxulub crater, support an asteroid impact.

The asteroid impact formed a crater and sent dust and soot into the air. Less sunlight meant less plant growth. Plant eaters then had less food, and animals that ate them were affected too. These changes affected places far from the crater over time. Some birds survived, even though all non-avian dinosaurs died out.

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

*Lesson, questions and flashcards written for this dataset.*

## 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)