Impact Crater Simulation
Big Idea:
Sixty-six million years ago, an asteroid roughly 10 kilometers across struck Earth with a force billions of times greater than any nuclear weapon. This activity models how impact size and velocity affect crater formation and debris distribution.

Materials:

• A large shallow tray or pan
• Flour, fine sand, or cocoa powder to fill the tray
• Small rocks or marbles of different sizes
• A ruler
• Optional: a second material to sprinkle on top (cocoa powder over flour, for example, to make ejecta visible)

What to Do:

Step 1: Set Up Earth
Fill the tray with a layer of flour or sand about 3 to 4 cm deep. Smooth the surface. If using two materials, sprinkle a thin layer of cocoa powder on top, this will show you how far debris travels.

Step 2: Make Predictions
Before dropping anything: if you drop a larger rock from the same height, will the crater be larger or deeper? What about dropping the same rock from a greater height? Record predictions on the lab sheet.

Step 3: Test Drop Height
Drop a marble from waist height into the tray. Measure the crater diameter and how far debris spread. Record. Now drop the same marble from shoulder height. Measure again. From full arm extension above your head. Measure again.

Step 4: Test Projectile Size
Drop a small marble, then a medium rock, then a large rock, all from the same height. Measure and compare craters.

Step 5: The Chicxulub Connection
"The asteroid that hit Earth 66 million years ago was about 10 km across and traveling at roughly 20 km per second. It hit what is now the Gulf of Mexico and released energy equivalent to billions of nuclear bombs. The explosion sent debris into the upper atmosphere worldwide, blocking sunlight for months. Without sunlight, plants died. Without plants, plant-eaters died. Without plant-eaters, predators died."

Step 6: Who Survived and Why
"Small animals that could burrow, hide, eat insects, or survive on stored food had an advantage. Large animals that needed enormous amounts of food every day did not. Birds survived. Non-avian dinosaurs did not."

Step 7: Discuss

• What pattern did you find between drop height and crater size? Between projectile size and crater size?
• If an asteroid that large hit today, which modern ecosystems would be most affected?

What's Really Happening (Caregiver Explanation):
The Chicxulub impactor struck Earth with such force that it triggered earthquakes, tsunamis, wildfires, and a global debris cloud that blocked sunlight for months to years. The resulting "impact winter" disrupted photosynthesis worldwide, collapsing food webs from the bottom up. A thin layer of iridium (a metal rare on Earth but common in asteroids) found in rock layers around the world at exactly the K-Pg boundary is the primary physical evidence for the impact. The iridium layer was discovered by Luis and Walter Alvarez in 1980. The crater itself was not identified until 1991, buried beneath sediment in the Yucatan Peninsula and the Gulf of Mexico.

Digging Deeper:
Research the Chicxulub crater off the coast of Mexico. How was it discovered, and who discovered it? Look up Luis and Walter Alvarez, who first proposed the asteroid impact theory in 1980. Their evidence was a thin layer of iridium found in rock layers around the world dating to exactly 66 million years ago. Why is iridium significant, and why did many scientists initially resist the asteroid theory?