# Earth's history in 4.56 meters: constructing a timeline with calculator tape

## Summary

A student activity. Students make a timeline of Earth's history using calculator tape. The tape is 4.56 meters long, so that one billion years is one meter. This activity is designed to have students get an introduction to the scale of Earth's history, gain a familiarity with some major events in Earth's history, learn about scaling, the metric system, and large numbers. This material helps illustrate the concepts of deep time and large numbers.

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## Learning Goals

• To create a timeline of Earth's history
• To gain familiarity with the metric system
• To make basic scaling calculations
• To increase knowledge of large numbers
• To become familiar with the order and rough timing (or numeric age) of major events in Earth's history
• To get a sense of the scale of human events compared to geologic events

## Context for Use

I use this as a short activity in a introductory geoscience class, early in the term. This takes roughly 45 minutes to an hour with introductory level undergraduates and works best when students work in groups of no more than 2. My classes have 24 students, but I think it would be doable with up to 50 if you had the space. It does help if there is enough supervision to catch mistakes as they happen rather than when students finish since mistakes will propagate along the timeline. You will need calculator tape (available at any office supply store) and meter sticks. Having long tables or open floor space is needed.

There are a couple of places where students can run into trouble.
• When they switch from events in billions of years to those in millions of years, they sometimes get stuck. I have them mark 500 million and 250 million years (one-half and one quarter billion years) so that they get the pattern.
• The end events are too crowded and they can't put them in. For some students, to be asked to do something that is not possible is scary for them. I always tell them to do their best and that indeed, that is one of the major points of the lab.
• Finally, I try to gather a group of students together at the end and ask them why I had them do this. They typically think that the goal is to make the timeline. I then draw out the other outcomes with them so that they see the 'point' of what they have done.

## Description and Teaching Materials

• Prelab (Microsoft Word 37kB Feb16 05) - This is a set of questions that I recommend students complete before beginning the activity to help it go more smoothly an quickly.
• Dates (Microsoft Word 52kB Feb16 05) This is a list of dates that I have the students put on the timeline.
• Student instructions (Microsoft Word 38kB Feb16 05) This is a set of instructions for students.

## Teaching Notes and Tips

I recommend that the students answer a couple of basic questions before beginning. This will greatly speed the activity. These could be given as homework.
1. How many millions are in a billion?
2. In this activity, you will make a timeline 4.56 meters long that represents 4.56 billion years of Earth's history. How long would 1 billion years be on the timeline? How many years would 100 centimeters represent? How many years would 1 cm represent?
3. Draw a line 1 cm long.

## Assessment

Assessment of this exercise can be unwieldy if the timelines are collected and later evaluated because each one will have to be unrolled and re-rolled. I recommend that each student present their timeline briefly to the assessor when they finish. Then the creator is responsible for unrolling and re-rolling the timeline. I grade on accuracy and completeness.

## References and Resources

Derived from Baer, E.A., Baer, E.M. and Whittington, C. 1999. Laboratory Manual for Physical Geology, Revised Printing. Kendall/Hunt, Dubuque IA.