1. Chapter 11
Plate Tectonics

2. I. Deformation- the bending, tilting or breaking of Earth’s crust
I. Deformation- the bending, tilting or breaking of Earth’s crust -Virginia’s Appalachian Mountains are example

3. II. Isostasy- balance between force of gravity pushing lithosphere down and the buoyant of the asthenosphere pushing up
Think of the Asthenosphere as a sponge
Think of the lithosphere as a weight on the sponge
a. If the mass of the weight is decreased, the sponge expands
b. If the mass of the weight is increased the sponge compresses
c. The forces on change slowly, but in the same way

4. III. Stress- the amount of force per unit area (example- pounds per square foot)
Compression- squeezing and shortening
Tension- pulling and stretching
Shear Stress- pushing parts of crust on different directions

5. IV. Strain- any change in shape or volume that is caused by stress
A. Permanent Stress
Brittle- materials that respond to stress by cracking or breaking
ductile- materials that respond to stress by bending or deforming without breaking

6. The composition of the rock determines whether it is ductile or brittle
Temperature and pressure determine whether rock is ductile or brittle
1. Rock near Earth’s surface is more likely to be brittle
2. Under surface, the rock is exposed to higher temps and pressure There it is more likely to be ductile.

8. B. Temporary Strain- rock deforms then goes back to its original shape when stress is removed

9. V. Folds- a bend in the rock layer
A. When rock responds to stress in a ductile way, folds are created.
1. Anticlines: a fold in which the oldest layer is in the center of the fold
Oldest

10. 2. Syncline: a fold in which the youngest rock is in the center of the fold

11. 3. Monocline: a fold where the limbs are horizontal, but one limb has moved up

12. VI. Faults- a break in the rock layers caused by stress in brittle rock
A. Size:
1. Can be a few layers of rock in a small region
2. Can be thousands of kilometers long
Fracture
Hanging Wall
Foot Wall

13. B. Normal fault- a fault in which the hanging wall moves down

14. C. Reverse fault- a fault in which the hanging wall is pushed up

15. C. Strike Slip Fault- a fault in which the walls slide past each other horizontally

16. I. Mountain Ranges and Systems
A. Mountain Ranges: groups of mountains in the same region that are the same age, structure and shape
B. How Mountains form:
1.Plate Collisions

17. i. Oceanic crust meets Continental Crust
Oceanic crust flows under continental crust
·Oceanic trenches are formed
·Friction of subducting plate heats up material above it
and cause magma to form
producing volcanic mountains on the over-
riding plate
Volcanic Mountains
Trench

18. ii. Continental crust meets continental crust
Folded Mountains
ii. Continental crust meets continental crust
crusts are about the same density, so neither subducts
crusts crumple and lift up forming high, folded mountain chains such as the Appalachian mountains
Plateaus are also formed

19. iii. Oceanic crust meets oceanic crust the denser crust subducts
mantle rock is melted, creating magma
·Forms underwater volcano chains
·Appear above water’s surface as
island arc volcanoes

20. iv. Continental Growth
-Terranes “get stuck” to existing
continents
·most present day continents are
made of cratons” (old, stable rocks)
with some terranes are identified by
rocks and minerals different from the
rest of a continent
-Terranes can be small sea mounts or
large chunks of continental crust