Illustrative Examples of Units of Practice

Understanding Geologic Time


The following unit of practice examines the geological past of the Earth by focusing on the Geological Time Scale. Students will create a time scale of their lives and, with the use of the Internet, examine the Earth’s time periods. Students will then demonstrate their knowledge through the use of a computer based program (Power Point) or a poster. Students will gain knowledge of past tectonic activity, and the Geological Time Scale. This will allow students to better understand the significance of a time period (eon, era, period, epoch) in the geological record and the importance of the boundary events.

Subject: Science

Learning Levels: Grades 7-9

Author(s): John Jennings


Students often have a hard time conceptualizing geological time and the events of the past. This unit will hopefully answer the questions "Have you ever wondered why have geologists divided the geological past into different sections?" and "Why do we know more about the last few million years of time than what happened 100’s of millions of years ago?"


Students will learn to work in-group settings.

Students will gain knowledge in designing presentations be they Power Point or posters.

Students will gain an understanding of Geologic Time.


This Unit of Practice takes between 4 and 6 hours of class time. The initial writing assignment can be discussed in small groups in order to facilitate the flow of ideas. The final project can be presented in two ways. If computer technology and the Internet are available, then information can be gathered and then presented with a LCD projector. If such technology is unavailable, most encyclopedias will carry the information and a poster can be created displaying the data. More time may be need if the students are to learn Power Point or a related computer presentation program.


The teacher introduces the topic by examining his/her life, charting the history and by delineating time periods with major events. Students are then asked to design a timeline of events in their lives. Students can initially work in groups to help facilitate the creation of possible topics and delineating events.

Once students have completed the above writing activity, a copy of the Geologic Time Scale is shown and discussed.

The students are then grouped to research one of the time periods (depending on the size of the class research can be done using eras, periods, epochs). Several appropriate web sites are listed below (See Tools). Students should examine major tectonic event, types of animals/plants, index fossils, and rock localities.

The data can then be presented using power point or can be displayed on a poster. This activity will take between 2 — 3 hours depending on the abilities of the class.


Students will discuss their writing assignments in a collaborative setting.

Students will examine several web sites that discuss geological time.

Students will work in their groups to develop their presentation on their specific time period.

Students will share information to the class in a formal presentation.


Students will be assessed on the completion of the initial writing assignment, and the successful completion of a PowerPoint presentation. They can also be assessed on class presentation and group work. Assessment of the presentation may also be facilitated by peer evaluation.


Computers with Internet hook up and Power Point and an LCD projector. The work can also be completed using encyclopedias and creating posters for display.


The following is a list of good web sites.

A good all around site

A site showing tectonic boundaries and ancient plate reconfiguration.