1. Lesson 2: Ancient Earth

2. ?? Essential Questions How did gravity affect Earth’s formation?
How did the oceans and atmosphere form?
What conditions made early Earth able to support life?
How did environmental changes affect the evolution of life?

3. Vocabulary Hadean eon Archean eon Protocontinent Proterozoic eon
Thermal energy

4. Earth’s Earliest History
Gravity and the Solar System
Before Earth or even the solar system existed, a cloud of gas, ice, and dust, called a nebula, floated in space

5. Earth’s Earliest History
First: Gravity pulled the particules together into a flattened disk shape and began to rotate.
Second: the material in the center became dense and the Sun formed
Third: the remaining pieces of material in the disk attracted each other and planets were formed

6. Spherical Earth As more particles come together Earth became larger.
Thermal energy is produced by collisions, which warmed the planet.
Asteroids continued to crash into the Earth surface, making it even hotter.

7. Hadean Eon, Archean Eon, Proterozoic Eon

8. Hadean Eon
The first 640 million years of Earth history

9. Hadean Eon The first 640 million years of Earth history
Formation of Earth’s Core
A hot Earth cools
Seas of Molten Rock
Changes in the Seas
The Ancient Athmosphere

10. Archean Eon
From about 4 to 2.5 billion years ago

11. Archean Eon
Earth continues to cool and first solid surface appeared, but still twice as much internal thermal energy was produced at that time, comparing to nowadays.
Volcanic Activity
As magma rised to the surface through cracks in the ocean floor it has formed Earth first oceanic crust.
The Earliest Continents
Protocontinents: small and early continents which have collided between each other forming bigger landmasses
Earth’s Oceans Form
Fossil bacteria and stromatolites are the earliest evidence of life present in rocks. They are uncommon and difficult to see due to their microscopic size.
The Archean oceans were extreme environments, most organisms alive today would not have survived then.

12. Proterozoic Eon
From 2.5 to billion years ago

13. Proterozoic Eon
Changes in the Atmosphere: Earth was cooling down and larger landmasses were formed.
Increase in Oxygen
Snowball Earth
Supercontinents and Shallow Seas
Proterozoic Life
Unicellular organisms in water.
First multicellular organisms in the ocean, but had no hard parts, so fossils aren’t abundant.

14. Homework
Textbook: Page 94 #2, 3, 4
Workbook: Page