James C. Firebaugh
Virginia Department of Education
P.O. Box 60
Richmond, VA 23216-2060

Level: 5th through 9th grade


Anticipated Learning Outcomes



  1. Review the concept of "scale" with students. The idea that a time scale will be analogous to a map scale should help to "set" the lesson and provide some advance organization.
  2. Practice using the scale 1 millimeter = 1 million years (first with single digits, then double digits, and so forth. See attached example.)
  3. When students have demonstrated mastery of scale conversion from linear measurement to scale "years," have them convert major events in Earth history from years before present into scale distances. Students should work in groups of two.
  4. After a list of events and their scale distances have been formulated, construct the geologic time scale on 5 meters of adding machine paper, beginning with formation of the Earth. Some sample events and their approximate dates are included on the attached page.

Results and Discussion

  1. Using their models, generate a discussion with the class around the following questions. A) How does the span of multicellular animal life on Earth compare with the total age of the Earth? B) Animals with backbones? C) Human beings? D) The Space Age?
  2. Have students find and record other events on the scale including major periods of extinction and mountain building. Relate these and other events to things such as to the positions of the continents.
  3. Have students evaluate the following statement: "Change is the only thing that is a constant."


Do not provide the scale distances for the students. Let them determine an appropriate conversion and evaluate their results.


Million Years Before Present

Distance in Metric Measures

The present 0


Ice Ages begin 1   ______________________
Earliest human 2   ______________________
Dinosaurs become extinct 65   ______________________
First birds 160   ______________________
East Coast of U.S. undergoes volcanic activity and earthquakes 190   ______________________
Dinosaurs begin to become dominant land animals 200   ______________________
Mammal-like reptiles 210   ______________________
First reptiles 285   ______________________
Appalachians being formed 290   ______________________
First amphibians 370   ______________________
Scorpion-like terrestrial animals 415   ______________________
First vertebrate animals 500   ______________________
First animals with shells 580   ______________________
Multicellular animals evolve 700   ______________________
Oldest known bacteria 3500   ______________________
Inferred age of the Earth 4500   ______________________

Practice examples (use scale of 1 millimeter = 1 million years)

 1 millimeter =  _____ million years
 5 millimeters =  _____ million years
 10 millimeters = 1 centimeter =  _____ years
 100 millimeters = 10 centimeters =  _____ million years
 1000 millimeters = 1 meter =  _____ million years

 416 millimeters =  _____ years
 3 meters =  _____ years

 100 million years =  _____ millimeters
 1000 million years =   _____ millimeters
 1 billion years =   _____ meters
 428 million years =   _____ millimeters

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