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Sedimentary Rocks
geology test #2
24
Geology
Undergraduate 1
02/28/2011

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Term
Weathering Controlling Factors
Definition
Climate
Soil
Parent Rock
Exposure
Term
Frost Wedging
Definition
water infiltrates crack, freezes and expands, splitting rock
Term
Exfoliation
-Isostatic Rebound
Definition
layers 'peel off'
-strata rise, pressure drops, rocks try to re-expand but begin to crack
Term
Agents of Erosion
Definition
water
wind
gravity
ice
Term
basin
-accommodation space
Definition
natural depression
-how much room there is in a basin
Term
subsidence
Definition
'sinking' of the crust, forms basins
Term
Lithification
Definition
process of compacting sediments under pressure
Term
Diagenesis
Definition
all the changes that occur during burial and lithification
Term
Compaction
Definition
sediments squeezed together
Term
Cementation
Definition
during compaction, pore water squeezed out
dissolved materials can precipitate & 'glue' sediment
Term
Recrystallization

Oxidation
Definition
unstable minerals can be altered into stable forms

breakdown of organic matter in presence of oxygen
Term
clastic sediments
Definition
produced by mechanical breakdown of rocks
-classified by grain size
Term
Sorting
-Poor
-Well
Definition
provides info on transportation
-variable energy, probably didnt transport far
-energy more constant, father travel
Term
Roundness
Definition
corners and edges get rounded during erosion via abrasion
-longer transport = more rounded
-harder minerals are more resistant
Term
maturity
Definition
combo of roundness and sorting
-rounder & better sorted typically imply longer transport
Term
Chemical Sediments
Definition
no mechanical breakdown
form via reactions

Rocks usually comprised of 1 major mineral type
-acid rain, saltwater evaporation
Term
Biogenic Sediments
Definition
produced by plants and animals
-shells make up the rock
-plants contribute to fossil fuel formation

as material is buried, water leaves, leaving C rich deposit
Term
Facies
Definition
sediment deposits characteristic of a particular environment
-features provide info about current direction
- fossils provide climate info
-mineral content provides burial conditions
- grain size reveals energy levels
Term
Mass wasting
-Controlling factors
Definition
transport of sediment & assoc materials downhill via gravity
-slope materials
-slope steepness
-slope wetness
-vegetation
Term
Angle of Repose
Definition
maximum 'steepness' that is relatively stable
-varies with material, shape of grain, & wetness of sediment
-larger flatter, more angular, wetter = more stable
Term
slope wetness
Definition
Too little- particles can move past another easily
too much-friction drop to point that material flows
just right-moisture adds surface tension that stabilizes grains
Term
Landslide
-rockfall, talus
-rockslide
-avalanche
Definition
mass wasting
-solid rock drops straight of slope, rock debris at base
-slide, rather than fall (slower)
-move lots of material downhill very fast (flows)
Term
Creep
-Solifluction
Definition
unconsolidated material slowly moves downhill (mm's/yr)
-creep caused by repeated freeze/thaw action
Term
Causes of mass wasting
Definition
Earthquakes
Over-saturation (snowmelt, storms)
Grading slopes too steadily
Removing vegetative cover
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