Download Minerals, basic component of rocks Minerals One Rock Common

Today:
• Apply chemical, physical
weathering
Minerals, basic component of
rocks
A naturally occuring inorganic
(usually) material with certain
physical properties
• Types of parent material
Minerals
•
•
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•
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Sulfides - pyrite (FeS2)
Oxides - hematite (Fe2O3)
Halides - flourite (CaF2)
Carbonates - calcite (CaCO3)
Phosphates - apatite (Ca5(PO4)3)
Sulfates - gypsum (CaSO4)
Silicates…...
Common minerals
Igneous + Metamorphic
Rocks
Light
• Quartz
– SiO2
• Muscovite
– KAl3Si3O10(OH)2
Dark
• Biotite
– KAl(MgFe) 3O10(OH)2
• Augite
– Ca2(Al,Fe) 4(Mg,Fe)4
Si6O24
One Rock
• Churt - high
in Si
• Dolomite Ca and Mg
carbonates
• Sphalerite ZnS
Weathering
Rocks Minerals Clays
• Rocks get broken down into smaller
and smaller pieces until the pieces
consist of single minerals
• These minerals small enough: silt
and clay fraction
• Hornblende
– Ca2Al 2Mg2Fe3Si6O22
(OH)2
1
Weathering
Rocks Minerals Clays
Physical Weathering
(disintegration)
• Result of Temperature
• Capacity to weather depends on
basic mineral composition
– Softer will break down faster
– Higher Fe, Mg will break down
faster
Physical Weathering
• Different minerals within a solid will
react differently to changes in
temperature
• Presence of water will accelerate
process
Physical Weathering
(disintegration)
• Result of Water, Ice, and Wind
Chemical Weathering
• Accelerated by:
– Water
– Oxygen
– Organic and inorganic acids
Chemical Weathering
(decomposition)
• All things that you don’t find in the
mantle
• Oxidation
2
Chemical Weathering
• Hydration - + H2O
• Solid + water = hydrated solid
– Al2O3 + 3 H2O
Al2O3• 3 H2O
Chemical Weathering
• Hydrolysis - H2O
H+ + OH• Solid + water = solid + ion + OH– KAlSi3O8 + 11 H2O
OH-
HAlSi3O8 +K+ +
Oxidation
Chemical Weathering
• Acidity - H+
• Solid + acid = ions
– CaCO3 + H2CO3
Ca2+ 2HCO3 -
Carbonation = Acidification
• Text calls weathering of rocks by
H2CO3 (carbonic acid) carbonation
• Process is one type of acidification
LEO - will occur in aerobic
environment
• 2FeS + 5H2O + 4.5 O2
+ 2H2 SO4-
2Fe(OH)3
Chemical weathering of
igneous and metamorphic
rocks
• Rocks higher in Fe and Mg will tend
to weather faster
• Will lose Fe and Mg in the process
• Fe in primary minerals is black
• As Fe oxidized (weathers) it
turns red like rust
3
KAlSi3O8
Basic Trends
Type of feldspar
• KAlSi3O8 + H20
HAlSi3O8 +K+ +OH-
• HAlSi3O8 + H20
Al2O3 +6H4SiO4
• Base forming cations (Mg, Ca, K) will
tend to go into solution
–Important source of plant nutrients
• Si will tend to form H4SiO4
–This is a soluble acid and will weather
• Al and Fe will tend to form oxide
minerals
Rock to Soil
Granite
Element
P
Ca
Si
Fe
In Rock
0.057
1.07
32.9
2.5
In Soil
0.035
0.23
21.8
8.54
Weathering process
%Change
-38
-79
-34
+242
Older soils
• Will have less soluble nutrients
• Will have more Fe and Al oxides
• Will have more ??? color
• Primary minerals
Secondary
minerals (including clays)
• Generally associated with loss of Si,
P, K, Mg…
• Increase in prevalence of Fe and Al
clays
Which mineral would you
expect to form a fertile soil?
• Quartz- SiO2
• Olivine - (Mg,Fe)2SiO4
4
Where would you expect
rocks to weather faster?
Where would
you expect
rocks to
weather
faster?
Both sites
(Alaska and Puerto Rico)
are wet
Higher temperatures in
Puerto Rico will
accelerate weathering
process
Puerto Rico,
Oxisol
Alaska, Gelisol
Where would you expect
more rapid chemical
weathering?
Where would you expect
more rapid chemical
weathering?
5
Desert vs Tropical
Rainforest
• Temperature regime is similar
• Water will accelerate
weathering process
• Physical weathering will be
predominant mechanism in
desert
Where would you expect
expansion of water due to
freezing to play a greater role
in weathering?
Utah, Aridisol
Puerto Rico, Oxisol
Where would you expect
expansion of water due to
freezing to play a greater role
in weathering?
Greenland vs Vermont
• For freezing water to play an
important role in weathering, it has to
thaw as well
• Freeze, thaw cycles accelerate
weathering process
Alaska, Gelisol Vermont, Spodisol
6
It may not seem like fun,
but….
• What process is going on here?
3MgFeSiO4 + 2H2O
H4Mg3Si2O9 +
SiO2 + 3FeO
• And here?
4FeO + O2
2Fe2O3
Nature of the parent
material
will greatly influence time it
takes to make soil and the
nature of the soil that is
formed
Colluvial debris:
Rocks that have fallen down
hills
Weathered Rocks from the
lithosphere are the parent
materials for soils
Types of Parent Material
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•
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Residual
Colluvial
Water
Ice
Wind
Organic material
Residual:
Parent material in place
Woodson soil series, KS
formed from sediment
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•
Water:Alluvial
deposits
Sediment that is deposited by rivers
•
Water:Alluvial
deposits
Sediment that is deposited by rivers
Water:Marine (sediments deposited
by oceans)
Water:Lacustrine (materials
deposited by lakes)
Glacial till:
Material
transported
by glacial ice
Pleistocene Epoch
2 million years
8
Glacial till: Material
transported by glacial ice
Paloose - eolian materials
Eolian:
Materials transported by wind
Loess
Eolian:
Materials transported by wind
Volcanic ash
Organic:Wet areas where
accumulation> decomposition
Peat bogs
9
(1)Parent materials + 4 other
factors of soil formation
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Climate
Topography
Time
Biota
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