1. Plate Tectonics
EQ: How do lithospheric plates move and how do they affect the Earth’s surface?

2. An Idea Before its Time
In 1912, Alfred Wegener proposed the idea of Continental Drift
He suggested that all of the continents were once joined together to form a supercontinent

4. Pangaea
Wegener called this super landmass Pangaea and believed that it broke apart 200 million years ago
Pangaea means “all land”
At first, his theory was not accepted
Unable to explain how the continents drifted apart

5. Evidence down the Road
Years later came important observations that supported Continental Drift
Fossil Clues- similar fossils found in South America and Africa and others found in Africa, Australia, India, South America, and Antarctica.

6. Evidence down the Road
Rock evidence- similar rock structures are found on different continents, such as this mountain belt that end at one coastline, only to reappear on a landmass across the ocean.

7. Evidence down the Road
Climate Clues- glacier deposits and rock surfaces shows that parts of South America, Africa, India, and Australia were once covered with glaciers

8. Quick Check: What is Continental Drift?
What 3 pieces of evidence support the idea of Pangaea?
The idea that all of the continents were once joined together
Fossils, Rock Clues (Mountains), and Glaciers

9. A New Theory Emerges
Wegener could not provide an explanation of exactly what made the continents move.
New technology lead to findings which then lead to a new theory called plate tectonics

10. This New Evidence…
With new technologies, scientists discovered a mountain chain on the ocean floor known as the Mid-Ocean Ridge
Mid-ocean ridges are underwater chains that run through Earth’s ocean basin
The Mid-Atlantic Ridge, the longest mountain chain in the world

11. Seafloor Spreading
Mid-ocean ridges are places where the sea-floor spreads
As tectonic plates move away from each other, the seafloor spreads apart and magma rises to fill in the gaps
The hot magma contacts ocean water, cools and hardens becoming new rock
This process is known as Seafloor Spreading

13. Plate Tectonics
The Theory of Plate Tectonics was developed in 1960s and combines the theories of Continental Drift and Sea-Floor Spreading.
Scientist believe the Earth’s crust and part of the upper mantle is broken into 12 sections that make up the plates which move on top of the asthenosphere

15. Convection Currents
Convection currents, originating deep within the mantle, provides the energy that drives plate tectonic
These currents rotate in circular patterns, carrying heat upward

16. Plate Boundaries
Divergent boundaries are the place where two plates move apart.
Convergent boundaries form where two plates move together.
Transform fault boundaries are where two plates slide past each other without the production or destruction of the lithosphere.

17. Convergent Boundary

18. Divergent Boundary

19. Plate Tectonic Discussion Questions:
Explain why Wegener’s theory of Continental Drift was not accepted at first.
Explain what is Plate Tectonics and what causes the movement of plate tectonics.
What are the 3 plate boundaries and describe them.