1. Plate Tectonics

2. Alfred Wegener
Alfred Wegener discovered that the eastern coast of South America and the western coast of Africa fit together like puzzle pieces
pieced all the continents together to form a super continent named Pangaea.
Using the remains of ancient organisms, showed that 200 million years ago the same kinds of animals lived on continents that are now oceans apart

3. Pangaea

4. Plate Tectonics Earths stiff outer shell is called the Lithosphere.
It consists of the crust and rigid upper portion of the mantle
Made up of 7 large pieces called tectonic plates.
The theory describing the movement of plates is called tectonic plates theory.

6. Why Do The Plates Move?
One hypothesis suggests that plate movement results from convection currents in the asthenosphere.
Asthenosphere is the hot, plastic portion of the mantle.
The Theory of Continental Drift-
Earth’s Crust and upper mantle are broken into plates an move around on the lower mantle (asthenosphere)

8. Divergent Plate Boundaries
A divergent plate boundary occurs where two plates move apart; a gap is created
Hot magma rises from the asthenosphere and cools forming new lithospheric rock.
The two diverging plates then pull the new lithosphere away from the gap.

11. Sea Floor Spreading
Mid-Oceanic Ridges are mountain ranges that form at divergent boundaries in oceanic crust.
Magma rises from between the two diverging plates and fills the gap.
New oceanic crust forms a large central valley, known as a rift valley.
The most studied Mid-Oceanic Ridge is the Mid-Atlantic Ridge.
runs down the center of the Atlantic Ocean from the artic ocean to an area off the southern tip of South America
Also found at Great Rift Valley (Eastern Africa)

13. Convergent Plate Boundaries
Can be an oceanic plate diving beneath continental or oceanic plates.
Andes Mountains is an example when India plate slammed into Asia plate
oceanic plate is more dense & dives beneath the continental plate.
This process is subduction
Ocean trenches, mountains, and volcanoes are formed at subduction zones
High temps and pressure cause plate to melt and form magma

14. Ocean Trenches Strange fish found 5 miles down
Sea cucumber 5 miles down
Deepest fish ever found in a trench.

15. Convergent Boundaries cont’d.
Collision zone – 2 plates of similar densities collide
Causes upward thrust, forming a mountain range
The Andes on the right and the Himalayas on the left.
2 types
Oceanic to Oceanic
Continental to continental
Continental-continental collision
Subduction zone

16. Convergent Boundary

17. Two Oceanic plates collide
Denser plate bends under the other forming subduction zone
Deep sea trenches form, new magma rises as an island arc of volacanoes.
Islands of Japan
Volcanoes and Earthquakes likely.

18. Two Continental Plates
Both plates less dense than asthenosphere,
No Subduction
Collide and crumple forming Mountain Ranges
Earthquakes Likely
Himalayan Mountains in Asia
Why no volcanoes?????

19. The Himalayas
The Himalayas are the tallest mountain range in the world.
They formed during the collision between the tectonic plate containing India and the Eurasian plate

20. Transform Fault Boundaries
The cracks in the Earth where the rocks move past one another are called faults
Faults can occur any area where forces in the lithosphere are great enough to break rock
When rocks move horizontally past each other at faults the boundary is called a transform fault boundary
Earth Quakes are caused by transform fault boundaries

21. Transform Continued 2 types
Two plates slide past one another moving in opposite directions
Two plates moving in same direction but at different speeds
Earthquakes likely
San Andreas Fault in California is Pacific Plate sliding past North American Plate
Each plate moves about 5 cm a year.

22. Transform Fault Boundary

23. Support for Tectonic Theory
As molten rock pours onto the ocean floor, iron minerals, such as magnetite, align themselves parallel to Earth’s magnetic field.
Earth’s Magnetic field has reversed direction many times during its history.
Differently oriented bands of magnetic rock
The rocks are youngest near the ridge
The rocks are older farther away from the ridge
Polar Wander Maps

24. Support con.’t
Rock formations on South Africa and South America have the same layers (these continents fit together in the puzzle)
Fossil evidence

25. Fit together like a puzzle

26. Boundary review
3 Types of boundaries: