Final Thinking Check

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FOSSIL HUNT COMPLETE

You successfully correlated rock layers across multiple locations using index fossils.

This is exactly how geologists determine the relative ages of rock layers.

Extension

Fossil Hunt

Use index fossils to match rock layers and determine their relative ages.

You are on a fossil hunt. Scientists have uncovered rock layers at three separate locations, and your job is to use fossil evidence to figure out which layers are the same age; and which came first.

Scientists use index fossils to estimate the age of rock layers and reconstruct Earth's history.

What Are Index Fossils? ▼

Fossils are the remains or traces of organisms from the past. Some fossils are especially useful for helping scientists determine the age of rock layers, these are called index fossils.

A fossil makes a good index fossil only if it meets all three of these criteria:

1
Lived for a short period of time; so its fossils only appear in a narrow band of rock layers.
2
Found in many locations; so scientists can use it to compare rock layers across different sites.
3
Easy to recognize; so it can be reliably identified in rock samples from the field.
Why This Matters

Fossils help scientists date rock layers without using a clock. They help compare layers found in completely different parts of the world. And together, they let geologists reconstruct billions of years of Earth history, one layer at a time.

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Practice
Field Investigation

Investigate a layer, then search for a matching fossil in a different location to link them.

Includes highlighted index fossils and fewer horizons.

Field Notes

Index fossils appear in exactly one layer per location. Your mission: find matching fossil horizons across all three dig sites, then determine which layers are oldest.

🔍 Find a match for: -
Game progress is not submitted Complete the puzzle and quiz, then submit to your teacher
Learning Science Focus Active Sense-Making Immediate Feedback Spatial Pattern Recognition Scaffolded Transfer
MA STE Standards · Grade 6–8 6.MS-ESS1-4 SP6: Explanation SP4: Data Analysis CCC1: Patterns
Go Further

More Learning

You used index fossils to correlate layers across sites and read the rock record like a timeline. Take that skill back to the framework it belongs to.

Lesson
Layers of Time
Return to the home lesson and revisit how geologists read the rock column to reconstruct deep time.
Lesson
Biological Evolution
Index fossils are snapshots of species that appear, thrive, and vanish. See what the fossil record reveals about how life changes.
Lesson
Continental Drift
Matching fossils on separate continents was one of Wegener's clues. See how the same evidence you used points to moving continents.