Geologic Time

When scientists used radiometric dating techniques to determine that the Earth is about 4.6 billion years old, it became necessary to develop a method to organize all of divisions of time on Earth. Geologists developed the geologic time scale to fulfill this need. This time scale is divided into eons, eras, periods, and epochs. A full study of the geologic time scale will provide a brief history of the planet. No study of geologic time is complete without exploring the fossil remains of organisms from each time period. In this topic, you will learn about the structure of the geologic time scale and explore the life that existed in each division of geologic time.

Essential Questions

• What are the major divisions of the geologic time scale?
• How are the eons, eras, periods, and epochs grouped on the geologic time scale?