Performance Objectives: Students should be able to:

·        read and interpret the geologic time scale

·        explain how a study of the fossil record shows that life forms have evolved throughout geologic time

Aim: What is the Geologic Time Scale?

Motivation: Making a Time Line of your life

·        Draw a long line across a sheet of paper to represent your life. Break it up into years. You can use a scale of 2 cm for every year.

·        Write each event in the correct year along the time line.

·        Now, divide the time line into parts that describe major periods in your life, such as preschool years, elementary school years, middle school and high school.

Procedure

1. Board Notes ( See Figure 1)
   • Geologic Time Scale is divided into eons, eras, periods and epoch.
   • Eons are the largest time units on the geologic time scale.
   • Eons are subdivided into eras based on fossil record.
   • Periods are named for locations and characteristic rock layers where rock of this age was studied.
   • Epochs are the smallest units on the geologic time scale. The epochs are subdivided into early, middle and late.

2.      Think About It

If you had to break up your time line into different groupings or divisions, what might they be?

Modeling the Time Scale

Using adding machine tape to make your own timeline. Have each centimeter equal 10 million years. Calculate the length or each era in centimeters. Draw lines on the tape to mark each era. Mark each of the events listed below. Add five other events to your timeline.

·        First fossils appeared 3.4 billion years ago.

·        First fish appeared 450 million years ago.

·        First reptiles appeared 290 million years ago.

·        Age of dinosaurs began 200 million years ago.

·        First mammals appeared 200 million years ago.

·        First birds appeared 150 million years ago.

·        First humanlike animals appeared 2 million years ago.

·        Last major ice age ended 10 000 years ago.