Fossils & Geologic Time
📋 What it is
Fossils in rock layers help date the layers and reveal Earth’s vast history in order.
🗣️ Coach says
Rock layers stack oldest-at-bottom, and the fossils inside them record which creatures lived when. Certain widespread, short-lived fossils ("index fossils") let geologists match and date layers around the world. Together, rocks and fossils reveal Earth’s enormous history in ORDER.
🧠 Memory hook
Layers stack oldest-bottom; fossils inside date them. Index fossils match layers worldwide.
😂 Giggle
What did the mid-ocean ridge say?
"I'm always spreading good vibes — and new seafloor!"
😲 Whoa!
A single thin layer of unusual clay found worldwide marks the exact moment an asteroid ended the dinosaurs — a geologic "bookmark" 66 million years old.
✅ Quick check: In undisturbed rock layers, which layer is usually the oldest?
Say your answer out loud first — then reveal.
The bottom one — layers stack up over time, so lower generally means older.
Superposition: lower layers are older.
🧪 Try it! (2 minutes)
Stack papers as "layers"; the bottom sheet went down first (oldest) — like rock strata.