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23
The End of the Dinosaurs
What could wipe out the most successful group of animals that ever lived?

An asteroid strikes Earth, volcanoes erupt, and the world changes in an instant. This is the dramatic end of the Cretaceous Period and the extinction of non-avian dinosaurs: one of the most pivotal moments in Earth's history. But it's not just a story of loss; it's also a story of resilience and survival. Your learner will see which animals made it through and why, and how their survival allowed new life to flourish in the epochs to come.

S2S_Lesson23 by Selene

Key Ideas

  • The Cretaceous–Paleogene (K–Pg) extinction was caused by a massive asteroid impact and volcanic activity.
  • Non-avian dinosaurs went extinct, while other lineages survived due to traits like smaller size, adaptability, or living in protected environments.
  • Survivors, including early mammals, birds, and crocodilians, allowed life to recover and diversify.
  • Catastrophes reshape ecosystems, influencing evolution and biodiversity.

Spine
  • DK's Science as You've Never Seen it Before: N/A
✏️  Notebooking Activity
Think of examples of animals that survived and ones that did not survive the K-Pg extinction event. Create a two-column chart (“Survived K-Pg Extinction” / “Did NOT Survive K-Pg Extinction”) and add some reasons why the survivors were successful.


Vocabulary
  • K-Pg Extinction — The Cretaceous-Paleogene mass extinction about 66 million years ago that wiped out non-avian dinosaurs and ~75% of all species.
  • Asteroid — A rocky body orbiting the Sun; a massive asteroid impact near present-day Mexico triggered the K-Pg extinction.
  • Impact Crater — A circular depression formed when a meteorite or asteroid strikes a planet's surface with tremendous force.
  • Iridium — A rare metal found in a worldwide rock layer dating to 66 million years ago; evidence for the asteroid impact.
  • Nuclear Winter — A period of cold and reduced sunlight caused by debris in the atmosphere after a massive impact; disrupted food chains.
  • Non-Avian Dinosaur — All dinosaurs except the lineage that evolved into birds; these went extinct at the end of the Cretaceous.
  • Avian — Relating to birds; birds are the only surviving dinosaur lineage and are classified as avian dinosaurs.

Cosmic CalendarWhere we are: December 30 · 6:24 AM
We are now precise enough on the Cosmic Calendar to give a time of day. Read the script below before the lesson.

Read aloud: December 30th, 6:24 in the morning. Look at how precise that is on our Cosmic Calendar. We’re not talking about a range of days anymore. We’ve narrowed it down to a time of day. About 66 million years ago, an asteroid roughly 10 kilometers across struck Earth near what is now Mexico’s Yucatan Peninsula. The impact released energy billions of times greater than the largest nuclear weapon ever built. The resulting fires, dust clouds, and climate disruption ended the reign of the non-avian dinosaurs. It happened fast, in geological terms. December 30th, early morning. One day and a bit left on the calendar. And out of this catastrophe, the small, warm-blooded, furry survivors are about to get their chance.

Timeline EntriesLabel the next page in your timeline “The End of the Dinosaurs: 66 Million Years Ago”. The workbook prompt asks learners to draw the Chicxulub asteroid streaking toward Earth with a fiery trail across the sky, and silhouettes of dinosaurs on the horizon below.

Discussion Questions
  1. What happened to most dinosaurs at the end of the Cretaceous?
    Sample answer: They died and went extinct.
  1. Which animals survived the extinction?
    Sample answer: Birds, crocodiles, and mammals.
  2. Why do you think some animals survived while others didn’t
    Sample answer: Some were small, could hide, or eat many different kinds of food.
  3. What does extinction mean?
    Sample answer: Extinction means all of a kind of animal or plant is gone forever.
Digging Deeper
  1. What evidence do scientists use to know that an asteroid caused a mass extinction?
    Sample answer: Layers of rock with high iridium, shocked quartz, and crater evidence show a large asteroid impact.
  2. Why did non-avian dinosaurs go extinct while birds  (avian dinosaurs) survived
    Sample answer: Birds were small, could fly, and may have had flexible diets, helping them survive environmental changes.
  3. What traits might help an animal survive a sudden catastrophe today?
    Sample answer: Small size, adaptability, ability to find food, and living in protected habitats.

Species to ResearchThis lesson focuses on who survived and who didn’t. Here are some species learners can research to understand both sides:
  • Tyrannosaurus rex— The most iconic of all predatory dinosaurs; lived right at the very end of the Cretaceous.
  • Ankylosaurus— A heavily armored herbivore with a club tail; another last-of-the-Cretaceous species.
  • Pteranodon— A large, toothless flying pterosaur; among the animals wiped out in the K-Pg extinction.
  • Elasmosaurus— A long-necked plesiosaur (marine reptile) that also went extinct at the K-Pg boundary.
  • Hesperornithes— A group of diving birds with teeth that survived alongside the non-avian dinosaurs, and then didn’t.

SCIENTIST SPOTLIGHT: Joanna MorganJoanna Morgan is a British geophysicist at Imperial College London who led the team that drilled into the Chicxulub crater, buried under the Gulf of Mexico, to collect rock cores from the asteroid impact that ended the age of dinosaurs 66 million years ago. The drilling project, completed in 2016, retrieved rock from deep inside the crater and confirmed key details about how the impact happened, how hot it was, and how quickly life began to recover afterward. Morgan’s leadership of this international project was a milestone for women in Earth science. Her work turned what had been an inference from thin lines of evidence into one of the most thoroughly documented events in Earth history.

Video:
Articles:
https://www.bbc.com/news/science-environment-41825471 
https://www.imperial.ac.uk/news/202573/prof-joanna-morgan-wins-barringer-medal/ 

Digging Deeper Activity:
What is an impact melt rock and why was it so significant to find it in the Chicxulub core? Research how the drilling was done in the shallow ocean above the crater. What other evidence, beyond the crater itself, do scientists use to confirm that an asteroid caused the mass extinction?

Sources and More Information:

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