Astrobiology in the Classroom


NASA – CERES Project –

Montana State University

Preliminary Edition




Geologic Time









The concept of timelines will be explored to gain an understanding of how events of the Earth’s past have shaped our home planet’s lithosphere and biosphere.  In these activities students will participate in activities to understand how the earth has evolved geologically and the vast amount of time that has passed since the earth’s accretion from celestial debris.  In order to understand how timelines are constructed students will first explore a “Learning Time Line” and be asked to consider how events in human development evolve sequentially.  Next, planetary evolution will be explored as students sequence and explain the geological and biological changes that have occurred on our planet over time.  In the final activity students will demonstrate their understanding of Geologic Time by creating timelines in various formats of the Earth’s past.



Part I – Exploration:


Using the “Learning Timeline Cards” for this activity, cut the cards and order the cards and according to a logical sequence, then discuss the results.


  1. Why do the cards belong in this order?


B.  How do age and physical size correlate to motor development and learning goals?


  1. How do the motor developments of one stage build on earlier accomplishments?


  1. Why does what is learned at each stage dependent on prior knowledge?


  1. Why are there no other logical ways to arrange the cards?


  1. If there were no ages on the cards, how would you know what order they belonged in?


Next, draw a line on the chalkboard or a sheet of butcher paper that is a meter long – 100 centimeters.  Using this line to represent the first 20 years of a person’s life, each year is 5 centimeters long. 


  1. If these cards were to be placed on the timeline at their proper point, where would each card belong? 


  1. How can this spacing be determined?



Part II – Concept Introduction:


Using current radioactive dating methods, scientists have determined the Earth’s age to be approximately 4.6 billion years old.  During this time the Earth, like a human during his or her lifetime, has gone through a number of changes.  Our home world has gone through various stages where the surface features and dominant lifeforms have evolved and changed.


Working in small groups, use the Geologic Time cards  distributed by your teacher, and cut these apart.  Use the ages given to place them in a logical sequence.  After completing this activity, discuss the results.  B arranging the cards by date you can construct a timeline of Earth’s history.  Review the names and dates for each era.


Using the 1 meter line drawn in the first activity to represent the first 5 billion years of Earth’s history, determine where each card should be properly placed on the line.   The proper scale should be 20 centimeters for each billion years.  Label each point with the correct name for each era.


Now that you are familiar with the names and stages of Earth’s past, what are the characteristics of each age?  From your teacher you will obtain both the Geology and Biology cards.  Again, working in groups, cut them out to complete the following task:


Determine which cards go with each era by sequencing the events for both sets of cards.


 Just like events in human growth and development depend on what is accomplished at previous stages, Earth’s geologic and biologic developments have evolved in a progressive sequence.  By using clues from the past stages you can see how Earth has evolved over time.


After completing this activity, you will be playing a game, “Wheel of Time” to create a class time line.  This game can be played individually in small groups or groups can compete with each other. Using a master set of geology and biology cards mixed together, draw cards randomly one at a time.  Roll a dice or use a simple spinner to determine the point value of that card.  As each card is drawn, identify the correct era that card belongs with and match it with the correct era card that has been placed on the timeline.  If the response is correct, that individual or team gets the number of points indicated by the dice or spinner, and the card is taped to the timeline at the correct era.  Take turns with each player or team getting a chance to place cards until all the cards are used and each era has a correct, corresponding biology and geology card.


After all cards are placed, discuss the results and address the following discussion questions:


A.  How did you determine what order each set of cards belonged in?


  1. How do the events at each stage build on what happens before?


  1. Which period was the longest? Shortest?



Part III – Concept Application:


To demonstrate an understanding of geologic time, you will work individually or in groups to create a timeline that includes the name, age, geologic features and biologic lifeforms for each stage in Earth’s history.  Select one of the following formats to complete this activity:


    1. Use adding machine tape and a scale of one centimeter equals 100 million years.


    1. Use a calendar format and determine the scale necessary to fit 4.6 billion years into one calendar year (12 months).


    1. Use a clock format and determine the scale necessary to fit a 4.6 billion year history onto a 12 hour clock.


After completion of the timeline, share their project with the class and consider the following questions:


  1. How long did it take for multi-celled animals to develop?


  1. Why was the formation of the Moon important for life on Earth?


  1. What if the Moon formed much later in Earth’s history?


  1. Why is it important that plate tectonics developed on Earth?


  1. How have Mass Extinction Events effected Earth’s biosphere?


  1. When did mammals arise?


  1. What does the evolution of the oceans and atmosphere have to do with the evolution of life?


  1. What is required for life on Earth?


  1. If events on the timeline are moved forward or back, how does the change effect other events or their timing?


  1. What if events were different on another planet?  How would their planet be different?


  1. If events are removed or new ones are added, how does it effect the ability of the planet to develop life?


  1. How rare do you think life is in the universe?












Geologic Time, Biology & Geology Cards: