Geologic Time Scale

Have students construct a geologic time scale of the major events of the birth of life on Earth. Using 46 sheets of white paper, tell students that each sheet of paper represents 100 million years. Have students record the major events that took place in Earth’s history.

4.6 billion years ago Earth was created.
4.5 billion years ago Earth’s moon formed.
3.8 billion years ago Bacteria arose.
3.6 billion years ago A cooling process began on Earth.
3.0 billion years ago Clouds formed.
2.0 billion years ago Eukaryotic cells evolved.
0.5 billion years ago Oxygen began to saturate the atmosphere.

Tape the time scale together and display it on a wall in your room. Ask students to use references to find more milestones in the Earth’s development. How long did it take for oxygen to form in the Earth’s atmosphere? How much space does the average human life span cover on the time line? Discuss other surprising developments revealed by the time scale.

The Discovery School Channel, http://discoveryschool.com/spring99/programs/birthofearth/activities.htm