Class Conference on the

Age of the Earth:

Creating a Timeline Based on Evidence


Timelines can be a powerful tool for student learning, both in organizing ideas and in understanding scale and sequence of events. This activity seeks to help students conceptualize the age of the earth by creating a scale timeline of Earth history as a class. The activity seeks to increase student involvement and engagement in the activity by giving each student a role to play. The end product of this activity is a class timeline that can be left up in the room and refered to as students continue to investigate the earth and its history.


Objective: Students will understand how the growing body of scientific research and evidence led to changes in the understanding of life on Earth.

Time: 45-60 minutes in class


Age Group: 7-8 grade

National Science Education Standards Addressed:


Running your Conference:

1. Explain to the class that today you are all researchers at an international conference of scientists throughout time. You goal is to analyze the evidence and determine the age of the earth. Ask students to estimate how old the earth is based on what they already know. Have them record thier estimate along with any pieces of evidence they are basing it on in the chart below.

Predicted Age
My Lifetime
12 years
Recorded History
2000 years
Leaf Fossils
30,000 years


2. Walk around the room with a hat/bucket. In the hat/bucket you should contain your 20-30 slips of evidence folded in half. The number of slips you will need will depend on the size of your class; you need one slip for each student. Have each student take a slip as you go around the room, but tell them not to look at their slip until told to do so.

3. Explan that at this conference each student will represent the reseach of a different lab or scientist and each has information from his/her own study to share with the group.

4. The teacher will begin the conference with some common knowledge information. This information could be the presence of man in the current day, the formation of Hawaii, or and/or evidence of a meteor impact at the end-Cretaceous mass extinction. Any evidence you chose to share can be used as introductory information. Mark these events on the long string at the front of the room, explaining that the string will serve as conference's running model of the history of the earth. Tell them that each researcher will have a chance to add their information to the group model.

5. After giving students your initial pieces of information begin going around the room. Have each student come to the front of the room and read the information about the research study on thier card. Have them speculate on how their information might change the model of Earth history at the front of the room and attach their card in the correct place on the timeline. Have each student record the information on their individual prediction chart and make a new prediction about the age of the earth.

6. Repeat step 5 as you go around the room. Engage students in inquiry about how new evidence fits in with old models of earth history. Let them discuss how some studies are consistent with one another and other studies are not consistent.

7. After each student has read their card, or as you reach the end of the class hour, bring the class together as a group to discuss the information presented and agree on an estimate of the age of the earth. Questions to address at this time might include:

8. The class timeline can be left up in the classroom for students to explore and refer back to later in the year. It can be a useful tool in placing later discussions of evolution or geology in context in time.

*For ideas about what pieces of evidence you might include on your timeline, see the Timeline Background Information for teachers or any of the fossil webpage links. Note that by showing many pieces of fossil evidence from that last few thousand years you can illustrate how our knowledge of the Earth is concentrated in recent years, but the history of the Earth dates back much further. Also, feel free to add studies or theories that were wrong or students may find outlandish. These can help spark student interest and initiate conversation about quality of evidence and critical thinking about data.



This lesson primarily seeks to illustrate for students how a growing body of research evidence causes scientists to form and modify hypotheses. Although this project also creates an in-class resource of information on the geological and biological history of the Earth and seeks to introduce students to this history, it does not seek to teach the specific events of Earth history. Later lessons in a unit or class may seek to delve into the details of different events in Earth history. Thus, assessment of this lesson should be based on student ability to understand a hypothesis and describe how a hypothesis must be modified as new information becomes available. This assessment can begin in a classroom discussion. However, homework questions specifically addressing key terms and ideas will provide clearer evidence of student understanding. Teachers may choose from the following homework questions:



For more ideas on using timelines in your classroom please follow the following links:


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