Dino Dating Dossier Worksheet Classified
Dino Dating Dossier
Department of Geologic Forensics | Case #ARCH-150
Investigator:
Date:
CASE BRIEF: THE SOLNHOFEN MYSTERY
A rare fossil specimen of Archaeopteryx —the "first bird"—has been recovered from the Solnhofen Limestone in Bavaria. While the fossil preserves incredible detail, its absolute age remains unconfirmed. Your task is to analyze samples of volcanic ash found in the layer immediately surrounding the fossil to determine its exact age using radiometric dating .
Lab Analysis Data
Variable Measurement Target Isotope Jurassium-150 (J-150) Half-Life (\(t_{1/2}\)) 50 million years Parent Atoms (J-150) 1,250 units Daughter Atoms (Lead-X) 8,750 units Total Atoms in Sample
Isotope Visual Guide
Parent (J-150)
Daughter (Lead-X)
"The parent isotope is unstable. It decays into the stable daughter isotope at a fixed rate over time."
Step 1: Calculate Isotope Ratios
Determine the percentage of parent atoms remaining in the sample using the formula below.
Workspace: (Parent ÷ Total) × 100
Calculated Percentage Remaining:
%
Step 2: Decay Curve Mapping
Plot the theoretical decay curve points on the graph. Then, locate your calculated percentage on the curve to find the number of half-lives that have elapsed.
100% 75% 50% 25% 0%
0 1 2 3 4
% Parent Isotope
Number of Half-Lives Passed
Number of half-lives passed:
Age calculation:
(# of HL × 50 Million Years)
Final Geologic Verdict
Based on the radiometric analysis of the volcanic ash, the Archaeopteryx fossil is approximately:
Million Years Old
Expert Interpretation
Explain how your calculated age for Archaeopteryx aligns with its role as a transitional fossil between dinosaurs and birds.
Dino Dating Dossier Answer Key Answer Key
Dino Dating Dossier
Case #ARCH-150 | SOLUTION GUIDE
Investigator:
TEACHER COPY
Date:
Current School Year
Lab Analysis Data (Solved)
Variable Measurement Target Isotope Jurassium-150 (J-150) Half-Life (\(t_{1/2}\)) 50 million years Parent Atoms (J-150) 1,250 units Daughter Atoms (Lead-X) 8,750 units Total Atoms in Sample 10,000 units
Teacher Notes
Students must add parent and daughter units to find the total (1,250 + 8,750 = 10,000).
The percentage should be exactly 12.5%, which corresponds to exactly 3 half-lives.
Final age should be 150 million years (Tithonian stage of the Late Jurassic).
Step 1 Solution
Workspace Calculation:
(1,250 / 10,000) * 100 = 12.5%
Percentage Remaining
12.5%
Step 2 Solution
Result Point
100%75%50%25%0%
01234
HL Count:
3.0
Calculation:
3 HL × 50M = 150M
Verdict Solution
150
Million Years Old
Sample Expert Interpretation:
"Archaeopteryx lived approximately 150 million years ago during the late Jurassic period. This absolute age places it as a clear intermediate fossil, appearing after basal theropods but sharing advanced avian features like asymmetrical feathers. Its timing supports the theory that avian evolution was well-established by the end of the Jurassic, predating the diversification of modern birds in the Cretaceous."
Dino Dating Slides Geologic Forensics Division
Deep Time
Detectives
Solving the mystery of Archaeopteryx using radiometric dating and isotope analysis.
The Mystery Specimen
In 1861, a stunning fossil was found in Germany: Archaeopteryx .
"It has feathers like a bird, but teeth and a long bony tail like a dinosaur."
The Core Question:
EXACTLY how old is it?
Fossil Recovery Zone:
Our Tool: Radiometric Dating
The Atomic Clock
Unstable Parent Isotopes inside volcanic ash decay into stable Daughter Isotopes .
This process happens at a perfectly constant rate—it never speeds up or slows down!
The Half-Life
A Half-Life is the time it takes for exactly 50% of the parent atoms to turn into daughter atoms.
Time = # of HL × Length of HL
Visualizing the Decay
100%
0 Half-Lives
50%
1 Half-Life
25%
2 Half-Lives
12.5%
3 Half-Lives
Today's Case Profile
Sample Info
Target Isotope: Jurassium-150
Half-Life: 50 Million Years
Lab Findings
Parent Atoms: 1,250
Daughter Atoms: 8,750
YOUR MISSION
Use these numbers to calculate the percentage of parent atoms remaining, then use the decay curve to find the age .
The Detective's Math
1
Find the Total
Parent + Daughter = Total Atoms
2
Find the Ratio
(Parent / Total) × 100 = %
Mapping the Evidence
Once you have your percentage, you'll plot it on your Decay Curve Graph .
1
Start on the Y-Axis at your percentage.
2
Move horizontally until you hit the curve.
3
Drop straight down to find the Half-Lives!
Ready to Reveal
the Past?
Complete your Dino Dating Dossier and prepare to announce your official geologic verdict.
Deep Time Detectives Teacher Guide Deep Time Detectives
Radiometric Dating Facilitation Guide
Teacher Resource
Lesson Summary
Students act as geologic forensic investigators to determine the absolute age of an Archaeopteryx specimen. Using a fictional isotope (Jurassium-150) designed for clean mathematical results, students will calculate isotope ratios, plot a radioactive decay curve, and derive the fossil's age. This activity bridges the gap between abstract exponential decay and tangible paleontological evidence.
Lesson Specs
60-75 Minutes
Pairs or Individuals
Math & Graphing focus
Learning Objectives
Understand Isotope Ratios
Define the relationship between parent and daughter isotopes during radioactive decay.
Calculate Absolute Age
Apply the half-life constant to determine how much time has passed since a sample's formation.
Interpret Decay Curves
Plot and read an exponential decay curve to find specific data points.
Paleontology Context
Place Archaeopteryx in the correct geologic period based on empirical data.
Facilitation Timeline
10 MIN
Introduction & Hooks
Use the Dino Dating Slides to introduce Archaeopteryx. Ask: "Why do we need a way to find absolute age if we already have relative dating (layering)?" Discuss the need for "clocks" in the rock record.
15 MIN
The Isotope Ratio Concept
Walk through the Parent vs. Daughter concept. Use the visual on Slide 4 to show how atoms transition. Emphasize that the total number of atoms remains constant, only their identity changes.
25 MIN
Dossier Investigation
Hand out the Dino Dating Dossier Worksheet . Monitor students as they calculate the total atoms (10,000) and the percentage (12.5%). Ensure students are plotting the decay curve points accurately before they try to find their result.
20 MIN
The Verdict (CER)
Distribute the Dino Dating CER Worksheet . Students synthesize their mathematical evidence into a formal scientific argument. Encourage them to use vocabulary like half-life , stable , unstable , and absolute age in their reasoning.
Common Roadblocks
Calculation Error: Students often divide Parent by Daughter instead of Parent by Total. Check that their denominator is 10,000.
Dino Dating CER Worksheet Forensic Report
Dino Dating CER
Geologic Investigation Summary | Case #ARCH-150
Field Agent:
Report Date:
Core Investigation Question
What is the absolute age of the Archaeopteryx specimen recovered from the Solnhofen Limestone?
Lab Data Summary
Parent (Jurassium-150): 1,250 units
Daughter (Lead-X): 8,750 units
Total Atoms: 10,000 units
Isotope Constants
Half-Life of J-150:
50 Million Years
Claim
State your conclusion. How old is the fossil based on your analysis?
Evidence
Provide the specific data and mathematical calculations that support your claim. Include percentages and half-life counts.
Reasoning
Explain the scientific principles. How does the concept of a half-life connect your data to your claim? Why can we trust radiometric dating to provide an absolute age?
Authorized Forensic Analysis Report
Document ID: CER-ARCH-SOLNHOFEN-150-Mya
Dino Dating CER Answer Key Teacher Key
Dino Dating CER
Instructional Guide & Sample Responses | Case #ARCH-150
Grade Level: 8-10
Subject: Earth Science
Claim: The Conclusion
1-2 Sentences
The Archaeopteryx specimen recovered from the Solnhofen Limestone is approximately 150 million years old, placing it firmly in the Tithonian stage of the Late Jurassic Period.
Evidence: Data & Math
Show all work
Calculation Steps:
Total Atoms 1,250 (Parent) + 8,750 (Daughter) = 10,000 units total.
Ratio (%) (1,250 / 10,000) * 100 = 12.5% of parent atoms remaining.
Half-Lives 12.5% remains after exactly 3.0 half-lives (100% → 50% → 25% → 12.5%).
Final Age 3.0 HL * 50 million years per HL = 150 million years.
Reasoning: Scientific Principles
Conceptual Link
Radiometric dating relies on the principle that unstable radioactive isotopes decay at a constant and predictable rate called a half-life. Because environmental factors like temperature or pressure do not affect this rate, it serves as an "atomic clock" within volcanic minerals.
In this investigation, the presence of only 12.5% of the Jurassium-150 parent isotope indicates that three distinct half-life periods have passed since the volcanic ash layer formed. Since each half-life for this specific isotope is 50 million years, multiplying the number of elapsed cycles by the half-life constant yields an absolute age of 150 million years. This scientific calculation provides a more precise absolute date than relative dating methods (like law of superposition) alone, which only tell us the order of events rather than specific numerical time.
Grading Checklist
CLAIM (2 pts)
States 150M years old clearly. Specifies Late Jurassic.
EVIDENCE (4 pts)
Includes math for total atoms, %, and HL count. All numbers correct.
REASONING (4 pts)
Explains half-life concept. Connects 3 HL to 50M each. Defines absolute age.
