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25 terms

chapter 16 weathering, erosion & mass wasting

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what does climate affect?
weathering rates, temperature and rainfall.
What modifies weathering
CO2 uptake
cycle of climate
Reduced Weathering rate-> leads to increase in atmosphere CO2->climate warming which increases weathering->weathering reduces CO2 in atmosphere as Co2 changes to HCO3- --> lower CO2 leads to climate cooling -> lower temperatures and decreases in atmospheric CO2 reduce weathering
weathering
refers to any process that eventually breaks apart rocks
erosion
refers to transport of weathering products after they have been broken a part
average igneous rocks weather by
mechanical fragmentation, chemical alteration, solution (dissolved rocks)
two types of weathering
chemical and physical (mechanical) weathering
What are all rocks exposed to
water or air with rate/degree controlled by - rock properties, rainfall and temperature, presence or absence of soil (vegetation) length of exposure (t)
how does time affect weathering
more weathing over time less weathering erosion and soil formation
mineral stability affect weathering
more mineral stability means less weathering for quartz less mineral stability means more weathering for feldspar
how does temperature affect weathering
less physical weathering , more chemical weathering when temperature increases, less chemical weathering more physical weatheirng (thermal expansion and contradiction frost wedging)
increasing amount of rainfall on weathering
more physical and chemical weathering when rainfall increases, fragmentation and erosion and dissolution of minerals less rainfall means less physical and chemical weathering less fragmentation erosion, and dissolution of minerals
rainfall acidity on weathering
more chemical weathering when acidity increases, more chemical weatheirng more dissolutions of minerals, less chemical and physical weathering less dissolution of minerals
increasing slope steepness on climate
the more slope increases more erosion, less chemical weathering, less erosion more chemical weathering
chemical weathering principle agent
water
why does chemical weathering occur
because minerals formed deep in Earth's interior are not stable at the surface of earth
What is Stability the reverse of?
bowen's reaction series (quartz which forms late in bowen series is very stable whereas olivine which forms early weathers easily)
thermodynamics
consider the stability of any phase or group of phases under specified conditions temperature,pressure, oxygen levels aqueous solutions, etc.
kinetics
consider the rates at which reactions will proceed
minerals stable under the conditions of their formattion are
often not stable at the earth's surface - persistence due to slow reaction kinetics
chemical weather dissolution
it involves dissolution or transformation of minerals, product solutes are carried away as dissolved load - ground coffee with water, turns to liquid coffee containing caffeine and other substances
primary reactions of chemical weathering
dissociation: NaCl = Na +Cl
hydration K-feldspar + H -> Ca2+ +HCO3-
Acid Base Reaction: CaCO3 +H+ -> Ca2+ HCO3-
oxidation: Iron (fe2+) o2 -> hematite and silica
Feldspar chemical weathering
an abundant mineral in many rocks , 2KalSi3O8 (feldspar) + 2H+ + 9H2O -> Al2Si2O5(OH)4 (Kaolinite) 2K+ 4H4Sio4
H+ can come from
carbonic, sulfuric, nitric acids
carbonic Acid forms when
CO2 and H2O molecules combine, carbonic acid ionizes to form hydrogen and bicarbonate ions, bicarbonate ions react with feldspar, to form Kaolinite clay