Lesson Plan

Geologic Time

An illustration showing geologic eras and systems.

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Grade Level:
Middle School: Sixth Grade through Eighth Grade
Lesson Duration:
60 Minutes
Common Core Standards:
Additional Standards:
NGSS: MS-LS2-4; MS-LS4-1; MS-ESS1-4
Thinking Skills:
Understanding: Understand the main idea of material heard, viewed, or read. Interpret or summarize the ideas in own words. Applying: Apply an abstract idea in a concrete situation to solve a problem or relate it to a prior experience. Analyzing: Break down a concept or idea into parts and show the relationships among the parts. Creating: Bring together parts (elements, compounds) of knowledge to form a whole and build relationships for NEW situations.


How does Earth's history compare with human history? If we condensed the entire history of the Earth into one calendar year, what date would the development of humans occur? When would the Tower have formed? When would life have started?


The geologic history of the Earth stretches back 4.6 billion years. A human life is a mere blink of an eye by comparison. A common analogy used to explain Earth history is a calendar year: if all of that history were condensed into 365 days, what dates would major events occur?

This activity uses that analogy by having your students construct a timeline, highlighting major events in Earth history. It also includes important geologic events related to the formation of Devils Tower.


Download the lesson plan above for a full description, background and procedure of the activity. You will need to download and print out the materials shown below, then cut out the cards for the activity. You and your students should have a basic understanding of geology and Earth science before starting this lesson.


Use this document to print out the materials for the activity. Printing instructions are on the first page.

Download Primary Materials - Date & Time and Event & YBP cards

One of the source materials used to develop this activity, published by the Kentucky Geological Survey. A good reference to augment the activity.

Download Table of Geologic Time

Lesson Hook/Preview

If we smashed all of Earth history into a single year, what date would humans have developed? What about the oldest life forms? Or the oldest rocks?


Download the lesson plan above (gold button near the top of this page). Follow the instructions within.

Consider doing this activity in a gymnasium or outdoors, by creating 365 squares to represent every day of the year. Instead of having squares, you could use the hash marks on a sports field - or put down tape in the gym - and mark the start of each month. This will create a great visual representation of the calendar that your students will be an active part of.


Geology - the study of the Earth's rocks and the processes which change them over time.

YBP - Years Before Present - the number of years before present-day, commonly used when discussing Earth history.

Additional Resources

The feature image above is courtesy of Ray Troll. His website is a great resource for humorous, science-based artwork.

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Last updated: November 20, 2017