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86 Cards in this Set
- Front
- Back
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Weathering
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Rock breaks down
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Erosion
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Physical removal at sources
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Transportation
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Movement of eroded particles from sources by wind, water, ice
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Effects of weathering
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- New Minerals
- Surface oxidation - Spheroidal weathering - rounds "corners" -Differential weathering- favors resistant rocks |
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Disintegregation of rocks =
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Physical weathering
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Frost wedging
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Type of Phsycial weathering where rock is pried apart along joints and water expands upon freezing
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Abrasion during transportation
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Type of Physical weathing by friction by streams, wind, waves, and glaciers where grinding reduces size but increases surface area
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Pressure release
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A mechanical weathering process in which rocks that formed under pressure expand on being exposed at the surface
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Unloading
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Pressure release of deeply formed rock with expansion of the rock body at the surface
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Sheeting
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The formation of sheet joints
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Exfoliation dome
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A large rounded dome of rock resulting when concentric layers of rock are stripped down fromt the surface of a rock mass
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Exfoliation
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Removal process of sheet joints
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Other Examples of Mechanical Weathering
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- Plant Growth
_ Burrowing animals - Crystallization Pressures (salt crystals can weather our sidewalks) - Extreme temperature changes- Fire |
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Mechanical Weathering increases...
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surface area and increases potential for more weathering...physical and chemical
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Surface Weathering is assisted by the roles of
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-Oxygen or Hydrogen ions from acid
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Hydrolysis
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- The reaction of any substance with water
_ Hydrogen ions attack and replaces other positive ions |
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Chemical Weathering is similar to the effects of...
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Acids
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Role of Acid
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Hydrogen ions in water
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Solution weathering
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- Calcite (in limestone) dissolves in acidic water
_ fluted (channeled) rock surface - caves |
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Carbonic Acid H2CO3
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CO2 + H2O -> H2CO3
H2CO3 -> H(+) + HCO3(-) in water |
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Chemical weathering of feldspar
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H(+) + feldspar -> clay mineral
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Weathering and climate
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Hotter / wetter = FASTER!
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Chemical weathering of other minerals
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Weathering concentrates diamonds
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Surface weathering is related to Bowen's Reaction Series
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- The temperature of crystallization reflect rates of weathering
- First to crystallize = first to weather! - High Fe content = more unstable at surface |
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Equilibrium
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reactions to surface temperatures and pressures
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Rocks decompose to
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form new substances and new minerals
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The higher the iron content of igneous rocks =
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the faster those minerals are to weather to more stable sedimentary minerals
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Hematite
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iron oxide produced by weathering
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Laterite
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tropical soil
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Harpan
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hard layer of soil
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A horizon
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zone of leaching soil
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Role of Oxygen in oxidation
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Fe in ferromagnesian minerals becomes oxidized to form sedimentary rocks
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Hematite 4Fe + 3O2 ->
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2Fe2O3 iron oxide/red
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Limonite wih water =
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Fe2O3 = nH2 O: n=1,2, or 3 geothite/ yellow (HFeO2)
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Soil
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- Unconsoliated material above bedrock
- Weathered material and organic matter ~ Supports plant life - Formed by weathering |
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Loam
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different grain sizes of soil
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loess
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fine grain wind blown deposit of silt and clay
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Climate
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The long term of precipitation and temperature of an area
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Soil Horizon layer order
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O, A, B, C
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Soil Horizon O
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Organice material just below ground vegetation
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Soil Horizon A
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Leaching by downward percolating H2O
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Soil Horizon B
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Accumulation of clay minerals (Fe oxides, and calcite)
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Soil Horizon C
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Fragments mechanically weathered from bed rock and some partially decomposed
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Pedalfer is formed from
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downward leaching
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Pedocal is formed from
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upward / evaporation
- Harpan: calcite or caliche |
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Buried soil =
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paleosols: records of past soil
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Factors of soil
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Parent rock, slope, and time
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Residual soil
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on bedrock or regolith (formed in place)
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Transported soil
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loess or alluvium (wind and water borne)
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Bauxite is a principal ore of...
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Al
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Organic activity
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Ao horizon organisms are important
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Preventing landslide
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- Preventing mass wasting of debris
_ Preventing rockfalls and rockslides on highways |
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Overloading
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excess construction on unstable slopes (...those homes in So. California)
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Undercutting
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cutting the loe of an unstable slope (highwy problems)
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Unstable dams
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the problem with the town of Kelly, Wyoming in 1925
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Debris fall
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- free falling mass of debris
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Rockfall
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- bedrock breaking loose on cliffs
- Talus - at the base of cliffs is the result of broken rocks |
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Debris Avalance
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- very rapid, turbulent flow of debris
_ this same speed and flow category could pertain to a broken up Rock Avanlanche |
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Earthflow
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- Primarily flow of debris
- May involve some water - May involve rational sliding (slump) - Scarp- left above fail mass - Hummocky surface in lower part - May be slow or fast |
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Classification of Mass Wasting
Type of Movement |
- Flow = Turbulent
- Slide = Coherent (Translational slide and rotational slide (stump)) - Fall = Moving through the air |
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Classification of Mass Wasting
Nature of Movement |
- Turbulent (internal/moving within itself)
- Coherent (bedrock) - Through the air |
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Classification of Mass Wasting
Rate of Movement |
- Extremely slow: 1mm/year
- Rapid: >100km/hour |
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Classification of Mass Wasting
Material |
- Bedrock
- Debris ("soil", sediment) |
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Mass Wasting
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- Masses of debris or bedrock moving downhill
- Landslides and slower movements - Driven by Gravity |
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Debris Flow
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- Motion taking place throughout moving mass
- May be so like: creep or solifluction - Or faster movements like Earthflow, Mudflow, Debris Avalance |
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Surficial Processess
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- Erosion, transportation, decomposition on the Earth's surface
- Landscapes created and destroyed - Involves atmosphere, water, gravity |
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Surficial Agents
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Mass wasting, running water (streams) glaciers, wind, water, waves, ground water
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Types of Flow
Creep |
- gentle slopes
- NOT considered a form of landslide - Vegetation slows movement - Very slow flow (<1cm/year) |
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Creeps are facilitated by
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water in soil or by freeze-thaw in colder climates
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Solifluction
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The movement of thawed surface soil or sediment over permafrost.
-occurs in cold climates only! -usually slow but may accelerate -NOT LANDSLIDING! |
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Permafrost
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"permanently" frozen ground
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Mudflow
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- Flow of watery debris- more water than in Earthflow and faster
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Mudflows occur when
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Vegetation is sparse or lacking
(Dry climates like deserts, volcanoes with pyroclastic flows: Lahars, or after forest fires) |
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Rockslide
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-Bedrock involved
- Sliding alone planes of weakness parallel to slope (Bedding planes, foliation planes, and fractures/joints in rock) |
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Debris slide
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Debris moving along a well-defined surface
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Controlling Factors
Water |
- Does add weight
- May lubricate some bedding planes to encourage slides |
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The increase in pore pressure in saturated debris...
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decreases shear strength
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Surface tension is unsaturated debris...
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increases shear strength
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Controlling Factors
Climatic controls |
- Ice
- Water - Precipitation - Vegitation |
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Controlling Factors (Gravity)
Shear force |
The force of gravity approaching slope angles
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Controlling Factors (Gravity)
Overcomes... |
shear strength (the material strength or the "stick" component)
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Controlling Factors of Mass Wasting
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- Slope angle
- Local relief - Thickness of debris over bedrock - Planes of weakness (in bedrock) ~Bedding planes od sedimentary rocks, foliation, joints or faults |
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Foliation
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Alignment in Metamorphic Rocks
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Joints or Faults
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Structural breaks in the bedrock
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Bedding planes, foliation, and joints and faults are all parallel to the slope which equals...
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most dangerous!!!
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Water in pore space is a...
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critical factor!!
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