Earth Mat Flashcards - Ch 12
relation of slopes to weathering
steep : short term and incomplete decomp
gentle : long term more thorough
The pressure exerted on buried rock objects at depth is referred to as
lithostatic pressure or confining pressure
the decrease in lithostatic pressure or load
unloading or confining pressure
fractures sub parralel to surface
sheet joints
sheet joints resembling onions
exfoliation
kind of frost action that occurs along fractures oriented steep to surface
frost wedging
kind of frost action that develops along bedding planes and/or sheet fractures
frost heaving
occurs when clays and micas expand and wetted
slaking
result from daily or seasonal changes in rock temp that cause significant amounts of disintigration
thermal volume changes / insolation
an example of interplay between disintigeration and decomposition where spaced rectangular joints develop into spheroidal forms
spheroidal weathering
most significant agent of decomposition
downward pecrolating water
occurs when a mineral or other soil component is wholly or partially dissolved during chemical decomposition
dissolution
Major decomp process
Dissolution
Ion Exchange
Hydrolysis
Hydration
Oxidation
Chelation
occurs when ions are directly exchanged between a mineral and a solution.
Ion exchange
is a chemical reaction between a mineral and water in which dissolved hydrogen ions and/or hydroxyl ions are added to form one or more new minerals.
hydrolysis
most abundant group of new minerals produced during chemical decomposition
clays
hydrolysis product of Feldspars? Mafics?
Kaolinite and Orthosilicic Acid
Pyrolusite and Orthosilicic acid
Orthosilisic acid is also known as
dissolved silica
involves the addition of water to a crystal structure during the reaction between a mineral and the aqueous solution.
Hydration
the anhydrous calcium sulfate mineral? its hydrated counterpart?
anhydrite; gypsum
the anhydrous iron oxide mineral? its hydrated counterpart?
hematite; goethite
chemical rxn where electrons are transferred from a cation in the mineral to an anion, increasing its valence
Oxidation
requirement of oxide mineral formation
loss of electrons
oxidation product of fayalite
hematite
oxidation product of rhodonite
manganite
hematite can also be the oxidation product of which sulfide
pyrite
how does hematite turn back to pyrite
through reduction rxn
combination with sulfate and the conversion of ferric (+3) to ferrous (+2)
organic hydrocarbon ring complexes produced by lichen and humus decay
chelates
how are chelates important in decomposition
highly soluble
binds to metallic elements
a process where chelated binds to metallic elements, which removes them from solution
chelation
mineral concentration in mineral water
exceeding 250 ppm
concentration of dissolved solids in natural rain water
10 ppm
taste of various ions found in water
Hydrogen - sour
Sodium - salty
Sulfates and Chlorides - Bitter
the process of adding soluble gypsum in breweries
burtonize
detrital sediments that resisted decomposition
resistates
the oppposite of resistates
New Minerals
states that the susceptibility of common igneous minerals is inversely proportional to their crystallization temperatures as summarized in Bowen ’ s reaction series
Goldlich ’ s rule
heavier minerals (SG > 2.8) least susceptible to decomposition
rutile, tourmaline, zircon
what happens when erosion rates are high
materials removed before significant decomposition
chemically unstable materials dispered on depositional areas
what happens when erosion rates are low
stays in source area, decomposes longer
resistant detritus delivered in areas of deposition
clay definitions
Compositional term : phyllosilicates
Textural term : < 0.004 mm diameter particle
Silica rich tetrahedral layers
S Layer / T layer
Gibbsite Octahdral layer
G Layers
Brucite octahedral layer
B Layers
Octahedral G and B layers can be called a
O Layers
The layer types only permit how many majour clay mineral groups
4
Two Layer (S-G) or (T-O) clays
Kandites
Basic kandite Layer
single tetrahedral layer bonded to a single octahedral layer
Kandites are somtimes referred to as
7 angstrom clays
example of a kandite
kaolinites
repeat distance between clay layers
d-spacing
three layer clays (S-G-S) or (T-O-T)
Illite
Illite layer
Single octahedral layer sanwiched between tetrahedral layer
it is where the paired cation susbstitution happend in illite clays
interlayer spance (//)
Illites are somtimes referred to as
10 angstrom clays
three layer clays (S-G-S) or (T-O-T) or (S-B-S)
Smectites
Smectite layer
Octahedral (G and/Or B) sanwiched between tetrahedral layers with highly expandable interlayer sites
repeat distance of smectites
10 to 21 angstroms
sodium rich smectite
montmorillionite
four layer clays (S-B-S+B)
chlorites
basic smectite layer
Brucite layer sandwiched between tetrahedral layer with an additional brucite layer with a different composition
smectites are somtimes referred to as
14 angstrom clays
Hybrid clays, which contain stacked layer sequences characteristic of more than one type of clay mineral, are called
mixed layer clays .
lack interlayer constituents due to pore waters or other chemical alteration
degraded clay minerals
Fe₂O₃
Hematite:
FeOOH
Goethite
FeOOH · nH₂O
Limonite
Mn(OH)₂
Pyrolusite:
MnO₂
Manganite
BaMnMn₈O₁₆(OH)₄
Romanechite
