Idea for Use in the Classroom

Earth has existed for 4.5 billion years. In that time, it has undergone amazing transformations as a variety of geologic processes have changed the planet.

Have students read the introduction to the infographic. Ask students, “Why does the author use the word ‘complex’ to describe the history of Earth?” Have students discuss events and concepts that have made Earth’s history complex. Next, ask students how scientists organize different time periods from Earth’s past. Have them look at the chart of different time periods in Earth’s history to find the answer.

Lead a class discussion asking students the following questions:

  1. How many years are tracked on this chart?
  2. What do you notice about the way this chart is organized? (You may have to help students realize the distinction between periods and eras.)
  3. Is the chart to scale? (If students think it is not, have them explain how they could reformat the chart.)
  4. What are significant events that occurred in Earth’s past that show up on the chart?
  5. What time period do you live in?
  6. How do you think scientists are able to determine the relative date of the fossils and rocks they find? (You may need to guide students to understand that the rock layers help scientists determine relative age. Younger rock layers, and material in it, form on top of older rock layers.)

In groups, you can have students compare and contrast different eras or time periods.



process of complete disappearance of a species from Earth.

geologic timeline

scale used by geologists used to divide the Earth's 4.6 billion year history into units of time.


study of the physical history of the Earth, its composition, its structure, and the processes that form and change it.


having to do with the structure of the Earth's crust.


text and graphics arranged in order along a line to give information about when events or phenomena occurred. Timelines are sometimes used on maps to give a better idea of how time relates to the data or theme represented.