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The K-Pg extinction: how the dinosaurs' reign ended

Science · Dinosaurs & Paleontology · ages 9-11

Name ______________________ Date ____________

Which group of dinosaurs died out completely in the K-Pg extinction?
- Non-avian dinosaurs, which were not birds
- All dinosaurs, including every kind of bird
- Only dinosaurs that were smaller than birds
A dinosaur fossil comes from a rock layer dated to about 66 million years ago. How does that time compare with the K-Pg extinction?
- Many millions of years before the K-Pg extinction
- At about the time of the K-Pg extinction
- Many millions of years after the K-Pg extinction
Evidence links a large asteroid impact to the K-Pg extinction.
Circle one: True False
Scientists find a thin rock layer from the time of the K-Pg extinction in many parts of the world. Which metal is unusually abundant in it?
- Iridium
- Iron
- Gold
What is the name of the crater linked to the asteroid that struck Earth 66 million years ago?
- Cretaceous crater
- Palaeogene crater
- Chicxulub crater
Why does the widespread iridium-rich layer support the asteroid impact explanation?
- Iridium is found only in dinosaur bones and never in Earth's rocks.
- Iridium is scarce in Earth's crust but richer in many asteroids.
- Iridium is found only in volcanoes and never in rocks from space.
Which event happened before the impact's dust and soot reduced sunlight around the world?
- The asteroid struck and made a crater
- Less sunlight slowed the growth of plants
- Less plant growth reduced food for animals
Leo says, "All dinosaur species died the moment the asteroid hit." Which correction fits the evidence?
- Birds also died out, but new birds appeared only after the skies cleared.
- No birds survived, and all dinosaurs died only where the rock landed.
- Some birds survived, and loss of sunlight disrupted food supplies.

Answer key

For grown-ups. Fold this page away before handing over the rest.

The K-Pg extinction: how the dinosaurs' reign ended W1-mt_QHKqckBdAk-s1

Non-avian dinosaurs, which were not birds · All non-avian dinosaurs died out. Non-avian means not birds. Some birds survived.
At about the time of the K-Pg extinction · Both dates are about 66 million years ago, so the fossil comes from around the time of the extinction.
True · Chicxulub crater and rocks from the time of the extinction support the asteroid impact explanation.
Iridium · The layer is rich in iridium. Its age and wide spread help link it to the asteroid impact.
Chicxulub crater · The impact formed Chicxulub crater near what is now Mexico's Yucatan Peninsula.
Iridium is scarce in Earth's crust but richer in many asteroids. · Many asteroids contain more iridium than Earth's crust does. A widespread iridium-rich layer dated to the extinction supports the idea that material arrived from an impact.
The asteroid struck and made a crater · The asteroid impact came first. Dust and soot then reduced sunlight, harming plant growth and food supplies.
Some birds survived, and loss of sunlight disrupted food supplies. · Some birds survived. Reduced sunlight also harmed plant growth and food supplies over time, affecting animals far from the crater.