1. Chapter 2- Essentials of Geology
PLATE TECTONICS
Chapter 2- Essentials of Geology

2. SLO’s for this chapter…
I will be able to discuss the view that most geologists held prior to the 1960s regarding the geographic positions of the ocean basins and continents.
I will be able to list and explain evidence Wegener presented to support his continental drift hypothesis.
I will be able to list the major differences between the Earth’s lithosphere and asthenosphere and explain the importance of each in the plate tectonics theory.
I will be able to sketch and describe the movement along a divergent plate boundary that results in the formation of new oceanic lithosphere.

3. The Continental Puzzle
Alfred Wegener
German scientist
proposed the Continental Drift
Continental Drift
The continents had once been joined together to form a supercontinent
Pangea
Broke into smaller continents 200mya
The Continental Puzzle

4. Wegener’s Evidence for Continental Drift
Fossil Evidence
Several identical fossils found on different landmasses
Mesosaurus
Reptile
Lived in freshwater lake and shallow bays
South America & Southern Africa

5. How does the distribution of Mesosaurus fossils provide evidence for continental drift?

6. Rock Types Matching rock types Mountain belts that are separated today
Appalachians  North America to Newfoundland

7. Ancient Climates Glacial deposits
When the ice melts, the mixture of sediment deposits carried by the glacier
Proved that ice sheets covered large area of southern hemisphere

8. What was the evidence that supported the hypothesis of the Continental Drift?

9. Rejection of Wegener’s Hypothesis
Main objection:
Wegener could not describe a mechanism capable of moving the continents
Tidal influence of the moon

10. What was Pangea?

12. Why did scientists reject Alfred Wegener’s continental drift hypothesis?

13. Theory of Plate Tectonics
Earth’s lithospheric plates move slowly relative to each other
Driven by convection currents in the mantle
Theory of Plate Tectonics

14. Causes of plate motion Convection currents within the earth
Magma moves upward by convection
Cooler, denser slabs of lithosphere sink into mantle

15. Plate motion Averages 1-5cm per year As fast as your fingernails grow
Earthquakes, volcanoes, and mountain building

16. Types of plate boundaries
Convergent
Form where two plates move together
Plates collide
Trenches, volcanoes, mountain ranges
“destructive” plates

17. Types of plate boundaries
Divergent
Found where two plates move apart
Spreading centers located along mid- ocean ridges
“Constructive” plates
Producing new oceanic lithosphere
Form Rift Valleys

18. Types of plate boundaries
Transform fault boundaries
Occur where two plates grind past each other
Does not destroy the lithosphere
San Andreas fault
Pacific plate moving past N. American plate
Earthquake activity