1. Geologic Time Scale (pg 6)

2. Geologic Time Scale (pg 6)
• A timeline of Earth’s history

3. Geologic Time Scale (pg 6)
• A timeline of Earth’s history
• Based on both relative dating and absolute
dating

4. Geologic Time Scale (pg 6)
• A timeline of Earth’s history
• Based on both relative dating and absolute
dating
• Divides time into eons, eras, and periods

5. Creating the Geologic Time Scale
• The divisions are based on changes in the
fossil record in different layers of rock

6. Creating the Geologic Time Scale
• The divisions are based on changes in the
fossil record in different layers of rock
• Scientists use radiometric dating to determine
the age of each rock layer

7. Eras
1. Precambrian: Covers almost 90% of Earth’s
history. Single-celled organisms

8. Eras
1. Precambrian: Covers almost 90% of Earth’s
history. Single-celled organisms
2. Paleozoic: Animals and plants appear. This
era begins with the “Cambrian explosion”
with many strange new types of animals

9. Eras
1. Precambrian: Covers almost 90% of Earth’s
history. Single-celled organisms
2. Paleozoic: Animals and plants appear. This
era begins with the “Cambrian explosion”
with many strange new types of animals
3. Mesozoic: Dinosaurs, mammals, and
flowering plants appear

10. Eras
1. Precambrian: Covers almost 90% of Earth’s
history. Single-celled organisms
2. Paleozoic: Animals and plants appear. This
era begins with the “Cambrian explosion”
with many strange new types of animals
3. Mesozoic: Dinosaurs, mammals, and
flowering plants appear
4. Cenozoic: Mammals become dominant