Smithsonian National Museum of Natural History

It's a Date

A Deep Time Lineages Activity

Activity Description


Knowing how scientists estimate the age of fossils is one of the most fundamental concepts of paleontology. In this activity, students will learn how to use relative and absolute dating techniques to estimate the age of a mystery fossil. 

  • Designed for group of up to 5 students each
  • Grades 3-8 or Ages 8-14
  • Activity should take 30-40 minutes to complete


Students are presented with a collection of fossils from the Turkana Basin in Kenya and asked to determine the age of a mystery fossil. They then see a hillside with stratigraphic layers where the fossils were found. With this reference, they arrange the fossils in relative order from youngest to oldest. They are then given absolute dates of ash layers that bracket the mystery fossil, so they are able to provide an age range. Finally, they are shown evidence from other hillsides in the area that show the earliest date for a fossil — Equus, an index fossil in Africa — that is found in a layer below the mystery fossil, enabling the visitor to narrow the age range even more. 

  • Understand how layers of rock form so that fossils found in lower layers are older than those found in higher layers
  • Understand that volcanic ash layers contain specific elements that can be analyzed to get absolute dates
  • Order fossils and rocks from different stratigraphic layers on a horizontal timeline from youngest to oldest
  • Use absolute dates and index fossils from layers surrounding a mystery fossil to narrow in on a date range for that fossil
  • Feel like they’re doing science. 

Science Standards (NGSS)

Life Science

3rd Grade

  • 3-LS4-1: Analyze and interpret data from fossils to provide evidence of the organisms and the environments in which they lived long ago.

Grades 6-8

  • MS-LS4-1 Analyze and interpret data for patterns in the fossil record that document the existence, diversity, extinction, and change of life forms throughout the history of life on Earth under the assumption that natural laws operate today as in the past.


Earth Science

4th Grade

  • 4-ESS1-1 Identify evidence from patterns in rock formations and fossils in rock layers to support an explanation for changes in a landscape over time.

Grades 6-8

  • 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.

Download Materials To Use in Your Classroom

You can print and play this activity using a basic color printer and a laminator, or you can choose to produce something a bit more durable and high fidelity with off-the shelf purchases, 3D printer and custom print shop. Find instructions for each option below.

It is advised that no more than 5 students engage in the activity at a time. Multiple copies may be necessary to have an entire classroom divide into groups that do the activity at the same time. 



  • 8.5x11" Paper
  • 11x17" Paper (optional)
  • Color Printer (optional)
  • Laminator (optional)
  • 2 magnets or popsicle sticks


Print, cut out, laminate and tape as necessary.


Download the very large, high-resolution files from this Dropbox folder.

Here is a list of the files:

  • Strata Board PDF: Send to printer
  • Timeline: Send to printer
  • Extra Pieces: Print, cut out, laminate and tape as necessary
  • Index Fossil Reference Sheet: Print and laminate
Resource Type
Hands-On Activities
Grade Level
3-5, 6-8
Learning Standards
Next Generation Science Standards
David H. Koch Hall of Fossils - Deep Time