Sedimentary Rock:

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Sedimentary Rock Clastic - particles deposited,
cemented like sandstone, shale Chemical -
precipitation out of solution like salt,
gypsum, some limestone Organic - accumulation of
parts of plants and animals - swamps (coal),
shells (limestone)
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Sandstone
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Conglomerate
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Breccia
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Coquina (ko-KE-na)
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Graded bedding
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Playa (dry basin salt flat)
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Salt mine
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Bonneville Salt Flats
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MAJOR FACTORS IN METAMORPHISM 1) Composition of
Parent Rock 2) Temperature 3) Pressure 4) Time 5)
Effects of fluids (water)
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Sandstone to quartzite
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Limestone to marble
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Start of Sun-driven part of Rock Cycle
WEATHERING ? Two forms Mechanical, Chemical
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Q? Why are the streets of Chicago much worse than
those of Houston each Spring?
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Q? Why are the streets of Chicago much worse than
those of Houston each Spring? Answer Frost
Action
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Q? Why are the streets of Chicago much worse than
those of Houston each Spring? Answer Frost
Action Q? Why are the streets of Chicago much
worse than those of northern Sweden?
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Q? Why are the streets of Chicago much worse than
those of Houston each Spring? Answer Frost
Action Q? Why are the streets of Chicago much
worse than those of northern Sweden? Answer
More freezing and thawing.
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Mechanical Weathering (1) Frost Wedging
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Mechanical Weathering (2) Plant growth
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Mechanical Weathering (3) Pressure release
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Mechanical Weathering (4) Large Temperature
changes (also forest fires)
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Mechanical Weathering (5) Growth of salt crystals
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• Chemical Weathering
• Dissolution
• Hydrolysis
• Oxidation
• More significant than Mechanical Weathering (in
  volume of rock affected)
• Especially dominant in wet climates

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Chemical Weathering (1) Dissolution First
CARBONIC ACID is produced as H2O CO2 --gt
H2CO3 Then the carbonic acid dissolves calcite
as H2CO3 CaCO3 --gt Ca2 2(HCO3)-
(Carbonic acid) (calcite) (dissolved
calcium bicarbonate)
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Q? (to be answered on field trip) Why are these
basins here?
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Chemical Weathering (2) Hydrolysis Addition of
water (often as OH- hydroxyl) to a rock to form a
new rock Turns FELDSPAR into CLAYS Greatly
affects Basalt and Granite (Feldspar is the
most abundant mineral in cont. crust, and clay is
the most abundant sediment in ocean and
continental crust)
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HYDROLYSIS First CARBONIC ACID is produced.
Then the carbonic acid dissolves the feldspar as
(for example) 4NaAl3Si3O8 4H2CO3 18H2O --gt
4Na 4(HCO3)- 8H4SiO4 Al4Si4O10(OH)8 (Na-pla
g.) carb. acid water (dissolved
components) clay Provides the clays
that form shale, the most abundant sedimentary
rock Provides the sodium for all the ocean
salt
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Hydrolysis Greatly accelerated in the presence
of acidic rain
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Chemical Weathering (3) Oxidation Addition of
oxygen to a mineral to form a new mineral Most
common is with iron gtgt RUST Minerals start as
OLIVINE, PYROXENE, AMPHIBOLE Minerals end up as
HEMATITE and LIMONITE Ex/ 2Fe2SiO4 4H2O O2
---gt 2Fe2O3 2H4SiO4 (olivine)
(hematite) (dissolved silicic
acid)
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This dissolved silica is deposited in the form of
cryptocrystalline forms of quartz such as chert,
which can form either inorganically, or
biochemically as the shells of diatoms or
radiolaria.
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Mechanical and Chemical Weathering work together.
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1.
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2.
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3.
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Weathering stability of minerals is the reverse
of the Bower reaction cycle, for the same reason
strength of covalent bonds of silica tetrahedra.
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An end product of weathering is SOIL.
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Soil varies as a function of latitude because of
climate differences.
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Soil Affected by bedrock type
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Soil Affected by slope.
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Soil Affected by vegetation
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Q? Why is cutting down rain forests to grow crops
a bad idea?
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A. Tropical regions have the worst soils in the
world (all nutrients have been washed down
through the soils by high rainfall.
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MASS WASTING The removal of weathered rock and
soil.
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1st Rule of Geology Rocks Fall Downhill
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Rockfall
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Rockfall
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Landslide
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Landslide
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Landslide
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Landslide
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Slump
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Slump
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Slump
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Slump
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Mudflow
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Mudflow
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Mudflow
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Mudflow (lahar)
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Creep
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Creep
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Creep
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Underwater flows
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Weathering/Mass Wasting Responsible for the
appearance of the land surface.
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