1. PLATE TECTONICS

2. Chapter 10 Section 1 Notes Continental Drift
Alfred Wegener , German scientist.
Proposed a hypothesis called “continental drift.”
The continents once formed part of a single landmass called a “supercontinent” which began to break up into smaller continents. (about 250 mya)

3. Evidence for “Continental Drift”
Fossils: if continents were once joined, fossils of same plants & animals should be found in areas once connected
Rock Formations: ages & types of rocks in coastal regions, matched closely; mountain chains seemed to continue across oceans
Climate: geologists discovered layers of debris from glaciers in S. Africa & S. America.. Too warm today to have glaciers

4. Wegener couldn’t figure out the “how” part
1950’s hypothesis by Harry Hess- “Sea-Floor Spreading”.. This was the missing link for Wegener’s hypothesis.
1960’s – “Paleomagnetism” .. Study of magnetic properties of rocks.
By the end of the 1960’s…all the data and hypothesis’s were merged to develop the theory of “Plate Tectonics.”

5. Chapter 10 Section 2 Notes The Theory of Plate Tectonics
Plate Tectonics: How and why continents move and the study of the formation of features in the Earth’s crust.

6. How Continents Move…
Lithosphere- crust and rigid upper part of the mantle.
Asthenosphere- ‘plastic’ layer below the lithosphere. Flows like putty!

7. Two Types of Crust Continental Crust Oceanic Crust
Made primarily from silica.
Less dense than oceanic crust.
Oceanic Crust
Made primarily from iron and magnesium.
More dense than continental crust.
What do these densities mean?

8. The Major Plates North American South American Nazca Pacific Antartic
African
Eurasian
Indo-Australian

9. The Earth is made up of a dozen or so major plates and several minor plates. Tectonic plates are constantly on the move. The fastest plate races along at 15 centimeters (6 inches) per year while the slowest plates crawl at less than 2.5 centimeters (1 inch) per year.

10. TYPES OF PLATE BOUNDARIES
DIVERGENT
CONVERGENT
TRANSFORM

11. Divergent Plate Boundaries
What does it mean to diverge?
Plates move apart
2 Types:
Ocean – Ocean
Continent – Continent
Predict what would happen as a result of
Ocean-ocean divergent motion
Continent-continent divergent motion

12. Ocean – Ocean Divergent Boundaries
Sea floor spreading creates a Mid-Oceanic Ridge.
Basalt
Undersea volcanoes

14. Continent – Continent Divergent Boundaries
Hot magma rises and causes the crust to split.
Causes the land to drop and form a deep valley.
Rift valley
As spreading continues, the rift valley will lengthen, deepen, and make a sea.
Red Sea

15. Africa’s Rift Valley & The Red Sea

16. Convergent Plate Boundaries
What does it mean to converge?
Plates are moving together.
3 Types:
Ocean – Ocean
Continent – Continent
Ocean - Continent
Based on the model below
Make some observations about what happens at convergent plate boundaries
Predict what would happen at these boundaries

17. Ocean – Ocean Convergent Boundaries
One oceanic crust dips below the other – subduction.
Forms an ocean trench.
Examples include volcanic island arcs such as Japan and the Caribbean.

19. Ocean – Continent Convergent Boundaries
Denser oceanic crust subducts below continental crust.
Causes mountains with volcanic activity
Examples—Cascade Mts. in Washington, Oregon, and California & Andes Mountains.

21. Continent – Continent Convergent Boundries
Continents will smash together, NO SUBDUCTION, making mountain ranges.
Examples include the Himalayas.

23. TRANSFORM BOUNDARIES Plates are sliding past each other.
Examples include the San Andres Fault in California.

24. Transform Boundaries Occurs when two plates slide past each other.
Examples include the San Andres Fault in California.

25. SAN ANDREAS

26. ALPINE FAULT BOUNDARY IN NEW ZEALAND

27. How is plate motion happening?
Scientist’s aren’t really sure!
They believe ‘convection’ is the main reason.
-Convection is the movement of heated material due to differences in density caused by differences in temperature.
The Earth is a convection system!
Heat (energy) comes from radioactive elements within the Earth’s core.

28. Chapter 10 Section 3 Notes The Changing Continents
Continents are always changing shape
Slow movements of tectonic plates change the size & shape
Rifting = process by which Earth’s crust breaks apart; can occur within continental or oceanic crust

29. Continental Growth
Continents change not only by breaking apart but gaining material too
Terrane = a piece of lithosphere that may be apart of a larger piece of lithosphere
3 characteristics that identifies a terrane
Contains rocks & fossils that differ from neighboring terranes
Major faults at the boundaries
Magnetic properties don’t match those of neighboring terranes

30. Supercontinent Cycle
Supercontinent cycle = process by which supercontinents form and break apart over time
Supercontinents form because plates move toward convergent boundaries & eventually collide..
Heat then builds under the supercontinent & rifts begin to form & eventually can separate apart.

31. Pangea Pangea formed about 300 mya
As the continents collided to form Pangea, mountains formed.
About 250 mya, Pangea began to break into 2 continents, Laurasia & Gondwanaland
These 2 continents eventually separated into our continents that we have today

32. The Future
If plates continue to move at current rate, in about 150 million years, a new supercontinent will form