Test 2 Flashcards
Stress is the…
Force acting on a rock to deform it
Uniform (Confining) Stress
Stress is equal in all directions
Differential Stress
Not equal in all directions
-This is what deforms rocks
Three types of differential stress
- Tensional
- Compressional
- Shear
Tensional Stress
Pulling apart of the rock
Compressional Stress
Squeezing together
Shear Stress
Slipping, twisting, or wrenching of the rock
Strain
Strain is the change in shape or volume of a rock that results from stress
Brittle deformation-Fracture
- Irreversible break
- Stress exceeds the ductile limit
Ductile Deformation
- Irreversible change in size or shape
- Volume and density may change
Dip
Angle from horizontal
Strike
The compass bearing of a horizontal line
Joints
Fractures created by tension in brittle rocks due to differential stress during tectonic interactions
Fault types
-Normal Faults
-Reverse Faults
-
Normal Faults
Hanging wall moves downward relative to footwall
Reverse Faults
Hanging wall moves up relative to footwall
-Created by compressional stress
Thrust Faults
- Special reverse fault
- Common in large mountain ranges
- Shallow dip angle, less than 45*
Strike-slip Faults
Principle movement is horizontal
-Caused by shear stress
Folds
Warps in rock layers due to ductile deformation
Synclines
- Warp downward
- Youngest Strata exposed along axial plane
Anticlines
- Warp upward
- Oldest layers exposed at center folds along axial plane
Monoclines
Dip in one direction
Complex Folds
- Application of shear stress
- Multiple folding events
Plunging folds
Occur when the folds axis is dipping or plunging
Limbs
Some folds are not the same, one dips more steeply than the other
Domes and basins
- Generally occur in continental interiors
- Broadly warped regions
- Roughly circular pattern of outcrops
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
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
Charles Lyell
- Emphasized long period of time
- Small changes over long time wrought substantial changes
- Instrumental in Darwin’s ponderings
Lord Kelvin
- Cooling earth
- Earth is 400-20 million yo
Relative dating
Ordering of events
Absolute dating
Scaling events (Chronological order)
Seven Relative Dating Principles
- Law of Superposition
- Original Horizontality
- Original Continuity
- Cross-cutting relations
- Law of Inclusions
- Baked Contacts
- Fossil Succession
Geologic timescale
Phanerozoic -Cenozoic (recent life) -Mesozoic (middle life) -Paleozoic (ancient life) Azoic -"Precambrian"
Unconformities
Boundaries between rock formations of different ages.
Climate
Long term conditions
Weather
Short term conditions
Seasons
Tilt of earths Axis
Composition of Atmosphere
Nitrogen, Oxygen, and Argon
Unique in our solar system
- Oxygen/Nitrogen
- Water vapor
Structure of Atmosphere
- Solar radiation heats the atmosphere
- Temp varied with latitude and altitude (wind and ocean circulation attempt to redistribute the temps)
Factors that determine climate
- Latitude
- Altitude
- Terrain
- Proximity to large water bodies
- Ocean currents
- Snow cover
Magnetoshpere
Keeps us protected from the sun’s solar wind (flowing ions) which would erode the atmosphere
Thermosphere
- Temp increases with altitude
- Charged ions formed
Mesosphere
Temp decreases with altitude
Stratosphere
Temp increases with altitude due to the ozone
Does not readily mix with troposhpere
Troposphere
Temp decreases with altitude
Turbulent flow of air, variable humidity
Atmospheric Pressure
- Air has very low density
- Column of air exerts pressure
- Atmospheric pressure drops rapidly with altitude
Water Vapor
- Atmosphere varies in evaporation and precipitation
- Traps heat
- Reflects incident solar radiation
Atmospheric Circulation
- Solar radiation produces differential heating of the earth
- Air masses move to balance global temperature
- Warm air rises, cold air sinks
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
Climate zones
- Climate impacts geologic processes
- Sedimentary rocks record ancient climates
Weathering
The physical and/or chemical alteration of rocks and minerals
Physical Weathering
- Physical breakage of rocks into smaller pieces
- Ice wedging
- Sheeting
- Tree roots and crystal growth
- No change in chemical composition
Chemical Weathering
-Proceeds by the removal or addition of chemical components to the minerals, changing the composition of the original material
Dissolution
Dissolving of material
Hydrolysis
Chemical breakdown due to water exposure
Oxidation
Combination of oxygen with one mineral to form a completely different mineral where one element has a higher oxidation state (higher ionic charge)
Mechanical and chemical weathering
Mechanical weathering enhances chemical weathering by producing more surface area
Spheroidal weathering
Decomposition is most rapid at corners
Differential Weathering
Caused by variations in weathering rater
Occurs over a broad range of scales
Types of mass movement
- Creep
- Solifluction
- Landslides
Creep
- Extremely slow movement of soil and regolith
- Heaving soil, expansion and contraction
- Wet-dry cycles
- Freeze-thaw cycles
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
Landslides
- Slump block
- Flow
- Debris slide
- Landslide (rock and debris)
- Rock slide
Slump block
- Spoon shaped slippage
- Block moves downward and outward
- Multiple slippage planes
- Bedding plane displacement provides evidence for movement
Flows
- Mixture of water, mud, and rock
- Flows downhill
- Water lubricates mass of soil and rock
- Boulders and buildings may be carried
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
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
Seven reasons for mass movement
- Gravity
- Fractures in uncosolidated rock and dirt
- Stability of slope
- The role of water
- Planes of weakness
- Climate-Rapid snow melt
- Fire removes vegetation
Mass movement triggers
- Earthquakes/vibrations
- Slope angle and undercutting
- Climate
- Volcanoes
- Human activities
Collecting/tributaries
Where water is collected before forming a stream/river
Transport/trunk stream
The rivers and streams which take the water to the ocean
Dispersing/distributaries
Smaller streams that empty the water to the ocean
Drainage patterns
- Dendric
- Radial
- Rectangular
- Trellis
Dendric
Vein like
Radial
Water draining off a mountain
Rectangular
Drainage in a rectangular pattern
Trellis
Drainage patterns in carved out canyons
Flow conditions
- Laminar (High/low water velocity)
- Turbulent (Upward force to transport sediment)
Sediment load
Material carried along by the stream
Suspended load
Fine particles in a stream or river
Bed load
Coarse particles in a stream or river
Dissolved load
Ions in solution
Erosion in river systems
- Abrasion/down cutting
- Headward erosion
- Slope retreat
Meandering stream
A stream that goes to and fro
Braided stream
Looks like a braid
Deltas
Deltas are dispersion systems
Alluvial fans
Form in arid regions where streams enter dry basins. Sediment is deposited as gradient decreases
Floods
Rivers flood from time to time, no matter what we do to stop them.
