The Missing Billion Years

About this resource

At the bottom of the Grand Canyon you can touch dark rock about 1.75 billion years old with one hand and the sandstone on top of it, only about 510 million years old, with the other. How do geologists know which rock is older — and where did over a billion years of rock go? Rock layers are pages in Earth’s history book — read them in order, match them across places, and you can organize 4.6 billion years. In this one-week, 6-level Geologic Time Scale & Rock Strata unit for middle school science (NGSS MS-ESS1-4), students investigate a real mystery, then use their evidence to crack the case.

The Missing Billion Years is part of Science Unlocked, a series of mystery-driven lesson sets. Every set opens with a real, surprising phenomenon, builds the science one level at a time, and ends with students solving the mystery in a claim-evidence-reasoning (CER) write-up.

Topics: geologic time scale, rock layers, fossils, claim evidence reasoning (CER), science phenomenon, review games.

What's included

• Teacher Deck (95 slides, PowerPoint). Answers are highlighted on the slides. Speaker notes tell you what to say and do, what to watch for, and how to support students or push GT students further. Prep slides and answer keys are hidden, so they skip during a slideshow.
• Interactive Student Deck (58 slides, PowerPoint + PDF). Students type in boxes, drag cards and check marks, and rate their confidence. Assign one copy per student in Google Classroom or your LMS.
• Google Slides versions of both decks. Click a button in the Google Slides Links PDF to make your own copy in Google Drive.
• Teacher Guide (26-page PDF). The standard, a week at a glance, a materials list, misconceptions to watch for, a run-of-show for every level, answer keys and sources.
• Student Printable (19-page PDF + a low-ink greyscale copy). The same tasks on paper in 12 pt type, for students without devices, sub days, or anyone who learns better with a pencil. Slide numbers match the Student Deck.
• Self-grading digital activity. SCORM 2004 and SCORM 1.2 packages for an LMS that accepts SCORM uploads, a web package, and a single HTML file that opens in any browser. Notes, sorts, matches, tables and multiple-choice items grade themselves, and students get a copy-and-paste backup of their work. A 2-page teacher quick start is included.
• Two whole-class review games that open in any browser: a Jeopardy-style game (6 categories, 30 clues) and Trashketball, where teams answer on whiteboards and then shoot for points.
• Kahoot! and Blooket import files. 56 review questions, one file per level plus an all-levels file, with a printable answer key.
• Start Here guide, HTML & SCORM how-to guide and Terms of Use, so you know which file to open first.

The 6 levels (about one 45–50 minute class each)

1. Pages in Stone. How strata form, superposition, original horizontality. Key activities: Great Unconformity mystery, layer-clue ordering.
2. Rock Detective Rules. Cross-cutting (dikes, faults, canyons), reading the Grand Canyon wall. Key activities: Canyon label, Broken Dike puzzle, event order.
3. Rock Stack Lab. Model deposition, intrusion, faulting, erosion; swap and decode. Key activities: Clay rock-stack lab, Lab Conclusion CER.
4. Matching the Pages. Correlation, key beds, index fossils, unconformities, Kentucky. Key activities: Two-site match, index-fossil sort, Kentucky Rock Pages.
5. Building the Time Scale. How the scale was built, boundaries, relative vs. absolute, scale. Key activities: Time-scale reading, 4.6 m time tape.
6. Crack the Case. Stretch HS-ESS1-6: Earth’s earliest history, final CER. Key activities: Evidence Detective, Stretch CER, Crack the Case CER.

Built for real classrooms

• Every level follows the same routine: "I can" targets with a confidence check, a warm-up, copy-it notes with a word bank, hands-on practice, a checkpoint students must pass to unlock the next step, and an exit ticket. A 10-item Mini Quiz wraps up the week.
• Level 1 opens with a Power-Up on the earlier-grade ideas this standard builds on (2-ESS1-1, 3-LS4-1, 4-ESS1-1, 4-ESS2-1).
• The last level includes a high school Stretch (HS-ESS1-6) that every student tries and advanced students can take further.
• Hands-on lab (Make & Break a Rock Stack). Student materials list: Modeling clay, 6 colors; Wax paper (your work surface); Plastic knife; Plain dental floss (about 40 cm); Ruler; Index card = your SECRET recipe. Safety notes are on the slides and in the Teacher Guide.
• Support is built in: word banks, sentence starters and support notes on the slides, plus GT extensions.

Standards

• NGSS MS-ESS1-4: Construct a scientific explanation based on evidence from rock strata for how the geologic time scale is used to organize Earth’s 4.6-billion-year-old history.
• SEP: Constructing Explanations and Designing Solutions · DCI: ESS1.C · CCC: Scale, Proportion, and Quantity
• Stretch: HS-ESS1-6
• CCSS connections: 6.EE.B.6, 7.EE.B.6, RST.6-8.1, WHST.6-8.2

Try the digital activity first

• Not sure the self-grading activity will work in your LMS? Download the FREE HTML & SCORM Sample and test it with your students before you buy.

Save with a bundle

• Earth's History & Plate Tectonics (4 sets)
• Middle School Earth & Space Science (15 sets)
• Science Unlocked Mega Bundle (all 89 sets)

Teach next

• The Seafloor Summit (MS-ESS2-1)
• Slow, Then Sudden (MS-ESS2-2)
• Fossils on the Ice (MS-ESS2-3)

More from Mystery Lab Learning

• See every Science Unlocked set, and follow to hear when new ones are added, at Mystery Lab Learning.

Good to know

• The illustrations in this resource were created with AI image tools, and AI tools helped draft the lesson text. Every slide, answer key and lab step was then fact-checked against the sources listed in the Teacher Guide and proofread.
• Kahoot!, Blooket, Jeopardy!, Google Slides and PowerPoint are trademarks of their owners. This resource is not affiliated with or endorsed by them.
• License: one teacher, for use with their own students. Please buy an additional license for each colleague who uses it.