1. Earth Science
Mr. G. Yannakoulias

2. Present Day Planet Earth
Earth as it appears from space at the present time
It did not always look this way
The age of Earth is about 4.5 billion years

3. The Birth of Planet Earth
About 4.5 b.y.a.
Our region of solar system was made of gas and dust debris from a star that existed in this region of the solar system but exploded in what is called a nova

4. Debris From Exploded Star Coalesced Over Time to form a “Planetesimal”
Gravity caused the rock debris to coalesce and form larger bodies of rock called “planetesimals”
Eventually this led to the formation of early planet Earth

5. Earth about 4.0 b.y.a.
This process continued for about a billion years
The Earth at this time resembled a hot ball of fiery lava

6. Cooling of Earth’s Surface
Eventually Earth cooled enough to form a crust on its exterior surface

7. Formation of Earth’s Oceans
Oceans were formed from Earth’s bombardment by comets that contain water hitting its surface
This happened over many millions of years

8. Volcanism and Formation of Earth’s Oceans
Volcanic activity on early planet Earth was frequent
This resulted in the formation of water vapor which also helped to form oceans

9. Earth at about 2.5 billion years ago
The Earth at this point was completely covered in water with very little if any land protruding

10. Formation of Land Masses
Volcanic activity continued helping to form continents and islands that exist today
The continents at that time did not look anything like they do today though

11. Earth’s Changing Surface
Earths surface features are not static
They are constantly changing even today
The change is so slow however that we think that it is and has always been the same but this is a fallacy— fixism is the idea that the Earth has always looked the way it does today

12. Earth’s Changing Surface Over Time

13. How Do The Continents Move Around?
If you can see the surface of the Earth you would notice that it is made up of a series of plates—sections of crust that are separate from each other
These plates are where you find crustal sections of continents as well as crustal sections of ocean
They move and slide past each other from pulling and pushing by forces below the Earth’s surface resulting in movement of continents or “Continental Drift”

14. Earth’s surface is made of plates

15. Alfred Wegener ( )
Noticed that the edges of continents fit together like pieces of jigsaw puzzle
He thought that continents were together in the past
His researched proved this to be the case
This was known as the Continental Drift Theory

16. Pangea
Wegener formed a map of the early Earth which fitted all of the continents together
This supercontinent is called Pangea

17. Wegener’s Hypothesis Met With Skepticism by Scientific Community
Wegener’s hypothesis was initially rejected by the scientific community in spite of evidence
He could not explain how continents could move which did not help him
Furthermore, scientists could not imagine what forces were needed to allow continents to move
Decades later it was revised and accepted after the discoveries of the ocean floor
Wegener’s hypothesis was the beginning of the development of the theory of Plate Tectonics

18. Plate Tectonic Forces and Plate Movement
Thick molten magma rises and falls due to convection
Since it is thick (i.e. viscous) it pulls the plates on the Earth’s crust with it
It even tears the crust in places as well

19. Your Task
Read Pages
Make notes in your textbook on this material
This will be your notes for this section of the course
Hint: Use the same headings they use in your textbooks and just jot down the important information in the different sections