Challenge How long have organisms been living on Earth?

Key Vocabulary: Geologic Time Scale Radiometric Dating Mass Extinction

Activity 92: Time for Change

ON the first day of school, how do you know when to go to each of your classes??

Scientists have broken Earth’s history into distinct sections of time, with each section defined by different characteristics

Geologic Time Scale categorizes and divides the history of Earth into a series of consecutive sections that are organized by periods of time

Geologic Time Scale

Radiometric Dating the analysis of certain minerals that contain radioactive elements, which over time decay into different elements. (This gives us ages of rocks/fossils)

Mass Extinction High rates of extinction for many species in a relatively short geologic time span.

Volcanic eruptions Tectonic activity Global cooling/warming Meteor strikes

The Earth has had 5 major mass Extinctions!!!

Reasons for Mass Extinction:

We estimate the Earth to be about 4.5 billion years old

That is a lot of time!! Think about how much has changed in the last decade!

How old is the Earth??

We are going to investigate your own history and construct a personal time scale.

Begin Part One of the Procedure (page F-17) and stop at Step 6

Glue in Student Sheet 92.1

Put your 6 Fossil Cards in order. Follow Procedure Steps 7-10

Glue in Student Sheet 92.2

Use the chart to construct your Geologic Timeline: Follow Step 11

Part 2

Geologic Event Time Cards – Follow Steps 14 and 15

When you are finished, Answer Analysis Question 4 with your group and record your answers in your notebook.

Mass Extinctions