1
Q
Stress is the…
A
Force acting on a rock to deform it
2
Q
Uniform (Confining) Stress
A
Stress is equal in all directions
3
Q
Differential Stress
A
Not equal in all directions
-This is what deforms rocks
4
Q
Three types of differential stress
A
- Tensional
- Compressional
- Shear
5
Q
Tensional Stress
A
Pulling apart of the rock
6
Q
Compressional Stress
A
Squeezing together
7
Q
Shear Stress
A
Slipping, twisting, or wrenching of the rock
8
Q
Strain
A
Strain is the change in shape or volume of a rock that results from stress
9
Q
Brittle deformation-Fracture
A
- Irreversible break
- Stress exceeds the ductile limit
10
Q
Ductile Deformation
A
- Irreversible change in size or shape
- Volume and density may change
11
Q
Dip
A
Angle from horizontal
12
Q
Strike
A
The compass bearing of a horizontal line
13
Q
Joints
A
Fractures created by tension in brittle rocks due to differential stress during tectonic interactions
14
Q
Fault types
A
-Normal Faults
-Reverse Faults
-
15
Q
Normal Faults
A
Hanging wall moves downward relative to footwall
16
Q
Reverse Faults
A
Hanging wall moves up relative to footwall
-Created by compressional stress
17
Q
Thrust Faults
A
- Special reverse fault
- Common in large mountain ranges
- Shallow dip angle, less than 45*
18
Q
Strike-slip Faults
A
Principle movement is horizontal
-Caused by shear stress
19
Q
Folds
A
Warps in rock layers due to ductile deformation
20
Q
Synclines
A
- Warp downward
- Youngest Strata exposed along axial plane
21
Q
Anticlines
A
- Warp upward
- Oldest layers exposed at center folds along axial plane
22
Q
Monoclines
A
Dip in one direction
23
Q
Complex Folds
A
- Application of shear stress
- Multiple folding events
24
Q
Plunging folds
A
Occur when the folds axis is dipping or plunging
25
Limbs
Some folds are not the same, one dips more steeply than the other
26
Domes and basins
- Generally occur in continental interiors
- Broadly warped regions
- Roughly circular pattern of outcrops
27
Catastrophism
- The earth is young
- Two chapters:
1. Short period where earth's features were created by supernatural forces
2. Human existence and decaying earth
28
Uniformitariansism
- Earth is old
- Earth has many chapters
- Earth's features are due to natural processes over long periods of time
- The present is the key to the past
29
Charles Lyell
- Emphasized long period of time
- Small changes over long time wrought substantial changes
- Instrumental in Darwin's ponderings
30
Lord Kelvin
- Cooling earth
| - Earth is 400-20 million yo
31
Relative dating
Ordering of events
32
Absolute dating
Scaling events (Chronological order)
33
Seven Relative Dating Principles
1. Law of Superposition
2. Original Horizontality
3. Original Continuity
4. Cross-cutting relations
5. Law of Inclusions
6. Baked Contacts
7. Fossil Succession
34
Geologic timescale
```
Phanerozoic
-Cenozoic (recent life)
-Mesozoic (middle life)
-Paleozoic (ancient life)
Azoic
-"Precambrian"
```
35
Unconformities
Boundaries between rock formations of different ages.
36
Climate
Long term conditions
37
Weather
Short term conditions
38
Seasons
Tilt of earths Axis
39
Composition of Atmosphere
Nitrogen, Oxygen, and Argon
40
Unique in our solar system
- Oxygen/Nitrogen
| - Water vapor
41
Structure of Atmosphere
- Solar radiation heats the atmosphere
| - Temp varied with latitude and altitude (wind and ocean circulation attempt to redistribute the temps)
42
Factors that determine climate
- Latitude
- Altitude
- Terrain
- Proximity to large water bodies
- Ocean currents
- Snow cover
43
Magnetoshpere
Keeps us protected from the sun's solar wind (flowing ions) which would erode the atmosphere
44
Thermosphere
- Temp increases with altitude
| - Charged ions formed
45
Mesosphere
Temp decreases with altitude
46
Stratosphere
Temp increases with altitude due to the ozone
| Does not readily mix with troposhpere
47
Troposphere
Temp decreases with altitude
| Turbulent flow of air, variable humidity
48
Atmospheric Pressure
- Air has very low density
- Column of air exerts pressure
- Atmospheric pressure drops rapidly with altitude
49
Water Vapor
- Atmosphere varies in evaporation and precipitation
- Traps heat
- Reflects incident solar radiation
50
Atmospheric Circulation
- Solar radiation produces differential heating of the earth
- Air masses move to balance global temperature
- Warm air rises, cold air sinks
51
Water Circulation in the Atmosphere
Atmospheric circulation moves water
- Evaporation increases with temp
- Warm air holds more water
- Warm air rises and moves towards poles as cold air sinks
52
Climate zones
- Climate impacts geologic processes
| - Sedimentary rocks record ancient climates
53
Weathering
The physical and/or chemical alteration of rocks and minerals
54
Physical Weathering
- Physical breakage of rocks into smaller pieces
- Ice wedging
- Sheeting
- Tree roots and crystal growth
- No change in chemical composition
55
Chemical Weathering
-Proceeds by the removal or addition of chemical components to the minerals, changing the composition of the original material
56
Dissolution
Dissolving of material
57
Hydrolysis
Chemical breakdown due to water exposure
58
Oxidation
Combination of oxygen with one mineral to form a completely different mineral where one element has a higher oxidation state (higher ionic charge)
59
Mechanical and chemical weathering
Mechanical weathering enhances chemical weathering by producing more surface area
60
Spheroidal weathering
Decomposition is most rapid at corners
61
Differential Weathering
Caused by variations in weathering rater
| Occurs over a broad range of scales
62
Types of mass movement
- Creep
- Solifluction
- Landslides
63
Creep
- Extremely slow movement of soil and regolith
- Heaving soil, expansion and contraction
- Wet-dry cycles
- Freeze-thaw cycles
64
Solifluction
- Creep that occurs in permafrost
- Melting of soil water occurs from the surface down
- Permafrost prevents downward percolation
- Surface soils become saturated and begin to flow
65
Landslides
- Slump block
- Flow
- Debris slide
- Landslide (rock and debris)
- Rock slide
66
Slump block
- Spoon shaped slippage
- Block moves downward and outward
- Multiple slippage planes
- Bedding plane displacement provides evidence for movement
67
Flows
- Mixture of water, mud, and rock
- Flows downhill
- Water lubricates mass of soil and rock
- Boulders and buildings may be carried
68
Debris slides
- Mass movement along a well defined slippage plane
- Landslide block moves as a single or group of units
- Rock type, orientation, and water content influence events
69
Landslide (rock and debris)
- Rapid movement of large blocks of rock
- Slippage plane usually associated with
- Bedding plane
- Joint plane
- Structural weakness
- Blocks generally degrade as they move
70
Seven reasons for mass movement
1. Gravity
2. Fractures in uncosolidated rock and dirt
3. Stability of slope
4. The role of water
5. Planes of weakness
6. Climate-Rapid snow melt
7. Fire removes vegetation
71
Mass movement triggers
- Earthquakes/vibrations
- Slope angle and undercutting
- Climate
- Volcanoes
- Human activities
72
Collecting/tributaries
Where water is collected before forming a stream/river
73
Transport/trunk stream
The rivers and streams which take the water to the ocean
74
Dispersing/distributaries
Smaller streams that empty the water to the ocean
75
Drainage patterns
- Dendric
- Radial
- Rectangular
- Trellis
76
Dendric
Vein like
77
Radial
Water draining off a mountain
78
Rectangular
Drainage in a rectangular pattern
79
Trellis
Drainage patterns in carved out canyons
80
Flow conditions
- Laminar (High/low water velocity)
| - Turbulent (Upward force to transport sediment)
81
Sediment load
Material carried along by the stream
82
Suspended load
Fine particles in a stream or river
83
Bed load
Coarse particles in a stream or river
84
Dissolved load
Ions in solution
85
Erosion in river systems
- Abrasion/down cutting
- Headward erosion
- Slope retreat
86
Meandering stream
A stream that goes to and fro
87
Braided stream
Looks like a braid
88
Deltas
Deltas are dispersion systems
89
Alluvial fans
Form in arid regions where streams enter dry basins. Sediment is deposited as gradient decreases
90
Floods
Rivers flood from time to time, no matter what we do to stop them.
Geology 101
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