Strata Secrets Worksheet Field Expedition Log
Strata Secrets
Geologic Timeline • Research Unit 1
Evidence Checked
Geologist Name
_________________
Date Assigned
____/____/2026
Station / Period
____
Official Briefing: Reading the Rock Record
Earth behaves like a giant history book. Every time wind, water, or volcanoes deposit mud, sand, and ash, they form layers called Strata /STRAH-tuh/. Over millions of years, these layers compress into solid stone.
To reconstruct Earth's history without a time machine, geologists use relative dating. The master key to this secret history is the Law of Superposition /soo-per-puh-ZIH-shun/. This physical law states that in an undisturbed sequence of rocks, the oldest layer is at the very bottom and layers get progressively younger toward the top .
Think of laundry in a laundry basket! The shirt you wore on Monday is at the bottom (oldest), and the shirt you threw in on Friday sits on top (youngest).
Strata Diagram A
Layer 3 (Top Layer)
Layer 2 (Middle Layer)
Layer 1 (Bottom Layer)
Undisturbed rock formation
Superposition Test
Based on the Law of Superposition, what is the age order of the three layers shown in Diagram A?
A Layer 3 is the oldest, Layer 1 is the youngest
B Layer 1 is the oldest, Layer 3 is the youngest
C Layer 2 is the oldest, Layer 3 is the youngest
STRATA SECRETS RESEARCH RECORD PAGE 1 OF 2
Sequencing Lab
Geologic Event Workstation
Examine clues, sequence layers, justify findings.
Rule: Oldest is always at the bottom!
1 Excavation Site: Grand Canyon Cut Visual Puzzle
Observe the geologic cross-section below. There are three horizontal sediment layers (Layer A , Layer B , Layer C ) and one lava intrusion (Intrusion D ) that melted straight through the bottom two layers!
Layer A (Top Layer)
Layer B (Middle Layer)
Layer C (Bottom Layer)
D
Geologic Sequence (Oldest to Youngest)
Write the letter of each layer or event in chronological order:
1. OLDEST Event:
2. Second Event:
3. Third Event:
4. YOUNGEST Event:
Constructing Scientific Explanations
Geologists don't just guess—they construct evidence-based explanations. Use the Law of Superposition and the Cross-Cutting Law (which says an intrusion is younger than any layer it cuts through) to prove your sequence.
Clue #1: Proving the Bottom Layer
I know Layer C is than Layer B because Layer C sits it.
Clue #2: Proving the Lava Intrusion (D)
I know Intrusion D is than Layer B because Intrusion D through it.
STRATA SECRETS RESEARCH RECORD PAGE 2 OF 2
Strata Secrets Slides GEOLOGIC RESEARCH AGENCY
Active Excavation
STRATA SECRETS
Reading Earth's layers like the pages of a giant stone book. Grab your field logs and get ready to decode relative age.
INTRODUCTORY BRIEFING SLIDE 1 OF 4
The Vocabulary Decoder
Step 1: Learn the Terms
CLUE A: STRATA /STRAH-tuh/
Multiple layers of rock or soil stacked on top of one another.
Sediment deposits settle in flat, parallel bands over millions of years.
CLUE B: SUPERPOSITION /soo-per-puh-ZIH-shun/
The physical rule that the oldest rock layer is ALWAYS at the bottom.
New layers pile on top of old layers. Bottom is oldest, top is youngest!
Identify these terms on page 1 of your Field Journal Worksheet .
STRATA SECRETS INSTRUCTIONAL DECK SLIDE 2 OF 4
The Rules of Relative Dating
Step 2: Apply the Geologic Laws
Layer A (Youngest)
Layer B (Oldest)
🔥 Cross-Cutting Law: If an intrusion cuts through layers, it is always younger than the layers it cuts!
Master Investigation Rules:
1
Look at the bottom layer. It was laid down first, so it is the Oldest .
2
Follow the strata up. Each layer above is younger than the one below it.
3
If magma cuts through them, that intrusion occurred afterwards .
📝 Geologist Key: Relative dating tells us if an event is older or younger , not the exact age in years.
STRATA SECRETS INSTRUCTIONAL DECK SLIDE 3 OF 4
Case Study 1: Grand Canyon Cut
Step 3: Solve the Sequence
Excavation Site Diagram
Layer A (Top Layer)
Layer B (Middle Layer)
Layer C (Bottom Layer)
D
🔎 Sequence the events from Oldest to Youngest .
Step-By-Step Solution Blueprint
1. IDENTIFY
Bottom layer is Layer C. It is the OLDEST.
2. SEQUENCING
Next is Layer B on top of C.
3. CROSS-CUT
Intrusion D cuts through B & C. It is younger!
4. EXPLAIN
Order:
Strata Secrets Teacher Guide Strata Secrets Teacher Guide
Science Division • Instructional Pacing & Modifications
Teacher-Facing File
Overview & Learning Intentions
This lesson targets Earth Science standards on relative dating (MS-ESS1-4) by providing students with an interactive, highly structured rock strata model. It focuses heavily on sequencing rules, graphic support, and written expression.
Focus Standard: MS-ESS1-4 (Analyze and interpret rock strata to reconstruct relative history)
Reading Goal: Decoding complex vocabulary terms via phonetic guides
Suggested Pacing
00-10m: Hook & Term Decoding (Slides 1-2)10-20m: Stratigraphy Rules (Slide 3)20-40m: Guided & Independent Solve (Worksheet Page 2)40-45m: Peer Check & Reflection
SPED & Executive Function Scaffolds
💡 Attention & Focus (ADHD): Read the short story context together. The worksheet breaks up sequencing from scientific arguments, chunking physical tasks.
✍️ Visual-Motor / Handwriting: Use large lettering boxes on Page 2 to isolate each letter answer. This minimizes spacing frustration.
🗣️ Expressive Language: Instruct students to verbalize why "D cuts through" to a partner first, helping them formulate their written sentences.
Critical Student Misconceptions
Misconception: Top is Oldest Students sometimes assume the top layer is the oldest because it's "exposed first." Emphasize that layers pile on top, like physical files.
Misconception: Cross-Cutting Order Students struggle to sequence intrusions. If a vertical intrusion cuts through Layer B, the intrusion is always younger than Layer B.
STRATA SECRETS TEACHER GUIDE PAGE 1 OF 2
Geologic Event Answer Key
Correct answers, calculation layouts, and sample written justifications.
Confidential Key
✓ Page 1 Checkpoint Option Key
Correct Answer: B (Layer 1 is the oldest, Layer 3 is the youngest).
Reasoning: According to the Law of Superposition, in any undisturbed rock strata, the deepest layer (Layer 1) was deposited first and is oldest, while the highest layer (Layer 3) was deposited last.
1 Grand Canyon Cut Sequence Solution
1. Oldest C
2. Second B
3. Third D
