Earth’s History

• How the earth works.

• How the earth has changed over time.

• Earth timeline activity.

• California geology.

Earth Structure

How the Earth Works:Plate Tectonics

The Earth’s Plates

Themes for Today

• The earth is very old.

• The earth is always changing.

Ages to Note

• 14 billion years - age of universe

• 4.5 billion years - age of earth

• 3.5 billion years - oldest know life on earth

• 544 million years - explosion of life

• 65 million years - dinosaur extinction

• 1.5 million years - first homo sapiens

Geologic Time Scale

Cambrian540 Ma

Permian270 Ma

Cretaceous 60 Ma

Present

North America: Plate Tectonics at Work

Timeline Activity

• Divide into groups of 2.

• Collect 4.5m of adding tape.

• Using the worksheet provided, measure out each time.

• Note that each time is the time from the present, not the previous time.

• Have fun!!