1. Metamorphic Processes I

2. Crustal Deformation
Changes in earth’s surface due to the folding, breaking, or flow of rocks
Due to pressures that rocks experience within the earth
Pressures can be due to changes in temperature or moisture, shifts in the Earth’s plates, sediment buildup or even gravity

3. Types of Pressure / “Stress” on the Crust
Compressional Stress
Forces that push inward or press upon rocks/layers
Tensional Stress
Forces that pull in opposite directions
Shear
Two forces acting parallel to each other but in opposite directions

4. Kinds of Crustal Deformation
Elastic
temporary
reversed when the source of stress is removed
Ductile
a permanent change to the shape or size of the rock that persists even when the stress stops
Brittle
results in the breakage of the rock

5. Factors Affecting Rock Strength
High
Low
1. Temperature
Molecules/bonds can stretch/move
Materials will be more ductile
Materials are more brittle
2. Confining Pressure
(Equal stress on the material coming from all directions)
Materials are less likely to fracture or break
Materials will be more brittle and tend to break sooner
3. Time
4. Rock Type
Some minerals, like quartz, olivine, and feldspars are very brittle
Others, like clay minerals, micas, and calcite are more ductile 
Dry rocks: more brittle
Wet rocks: more ductile

6. Ductile Deformation Cause FOLDS
Kinds of Folds: Monocline, Anticline, Syncline, Plunging
Monocline
Anticline
Syncline
Plunging
Slight bend
Upward fold
Downward fold
Occurs if the fold axis is not horizontal 
The 2 sides of the bend are still horizontal
The 2 sides of the fold dip away from the center of the fold
The 2 sides of the fold dip inward toward the center of the fold
Folds are caused by compressional stress

7. Ductile Deformation Cause FOLDS
More Folds: Symmetrical, Assymetrical, Overturned, Recumbent
Symmetrical
Assymetrical
Overturned
Recumbent
The 2 sides of the fold dip away from the center at the same angle
The 2 sides of the fold dip away from the center at different angles
The layers on one side of the fold have been folded beyond 90⁰, making it go nearly upside-down
More extreme than an Overturned fold where the central axis of the fold is almost horizontal

8. Ductile Deformation Form Structures
Ductile Structures: Domes, Basins, Hogbacks
Dome
Basin
Hogback
Looks like an upside-down bowl
Looks like an upright bowl
A long narrow ridge
Due to compression and uplift
Due to compression and down-warping
Formed when inclined (monoclined) sedimentary rockbeds are eroded, while the harder rock layers on top resist erosion.
Hogback

9. Brittle Deformation Joint Fault
When rock layers are placed under a high enough stress, they can then fracture or break. Such fractures create either:
Joint
Fracture in rock that show no slippage or offset along the fracture
Fault
Fracture shows slippage or
offset along the fracture
Joints and faults can be caused by various stresses: compression, tension, shearing

10. Brittle Deformation Types of Faults
Dip Slip Fault
has an inclined fault plane
the displacement or offset is along the dip direction
Can either be:
Normal Fault
Tension acts in opposite directions. One block is displaced up and the other down 
Reverse Fault
Compression causes one block to be pushed up and over the other block
Thrust Fault
A special type of Reverse Fault with a dip below 45⁰, which can cause much more displacement of a much larger area
Strike Slip Fault 
has a vertical fault plane
Shear stresses are exerted parallel to each other

11. Brittle Deformation Structures Formed
Graben
produced when tensional stresses on adjacent normal faults result in a block of rock dropping down
Half-Graben
Bound by only one normal fault with a curved fault plane which can cause the down-dropped block to rotate
Horst
produced when compressional stresses on adjacent reverse faults result in a block of rock being pushed up
Also called a Fault-Block Mountain
Fault Scarp
The exposed cliff-like face of the fault plane

12. Sources http://www.tulane.edu/~sanelson/eens1110/deform.htm ml
hogback?guid=807b64fe-09d3-474a-99d0-e2bd224f0c08