Reading Earth's Pages: Rock Layers and Fossil Evidence
Shared by A STEM Educator
Students will construct written CER arguments explaining how the relative position of rock layers and index fossils provides evidence about Earth's history, environmental changes, and the age of rock formations.
Lesson Overview
Students investigate sedimentary rock strata and fossil evidence to reconstruct Earth's history, applying the CER framework to argue how geologists use rock layers to locate groundwater aquifers and trace historic climate shifts.
Materials
- Printed Grand Canyon cross-section photo (one per pair)
- Rock Layer Sequence Cards (set of 4 per group)
- Rock Core Diagram handout (multi-strata with index fossils)
- Color pencils or markers
- CER writing frame handout
- Consolidation note sheet (one per student)
- Exit slip slips (half-page)
- Sticky notes (2 per student)
Scaffolded Task Progression
Your team has four Rock Layer Cards (A, B, C, D). Each card shows a rock layer with a description of what it contains.
Arrange the cards from oldest (bottom) to youngest (top).
Then complete this claim:
> *I claim that layer ___ is the oldest and layer ___ is the youngest. I know this because layers that form first end up at the ___.*
Write your team's sequence here: ___ → ___ → ___ → ___
(oldest to youngest)
A geologist drilling a rock core in Arizona finds the following layers from top to bottom:
- Layer 1 (top): Light tan sandstone, no fossils
- Layer 2: Gray limestone with coral fossils
- Layer 3: Red mudstone with fern fossils
- Layer 4 (bottom): Dark shale with trilobite fossils
Write a claim sentence identifying which layer is oldest and which is youngest. Use the word *superposition* in your claim.
[ Interactive graph / diagram — available in the full lesson ]
Unlock the full lesson
See all 6 scaffolded tasks, the full answer key, warm-up, exit slip, and a print-ready version — free to start.
Create a free accountAlready have an account? Sign in
Like this lesson but want to tweak it?
Make an editable copy and adjust the tasks, warm-up, and answer key to fit your class — no need to start from scratch.