Weathering

define solubility

- amount of mineral dissolved in saturated solution - point at which mineral will not dissolve anymore

What's the functions of solids? - regulate.. - serve as medium for .. - filter, store and supply... - support recycling of ... ...

- composition of the atmosphere - serve as medium for plant growth - filter store and supply water - support recycling of organic matter

what happens to the ferrous ion ? example ?

- electrons are transferred from Fe 2+ to O2 - producing Fe 3+ which combines with water to form iron oxide and iron hydroxide minerals - hematite, ferrihydrite (hematite is not a silicate tehse are products)

hot and humid

- formulation of insoluble residues with crusts of iron oxide and aluminum oxide

weathering mechanisms - physical and ____ weathering causes the rock to ____ and _____ - chemical weathering attacks ____ _____ and weakens rocks - as a square progressives into a cube what part is attacked at the most sites

- fracture and fragment - exposed surfaces and weakens rocks - the corner is attacked by three sides

describe the uplift weathering hypothesis

- global rate of CHEMICAL weathering is dependent on the availability of fresh rock - mountain chains at convergent boundaries enhance weathering - as new silicate rich crust is exposed to weathering, atmospheric CO2 is consumed and the climate cools

weathering rates vary among rock types and are determined by four factors:

- properties of the parent rock, harder rocks weather slower - climate (hot climate promotes more weathering) - presence of absence of soil (soil protects) - length of exposure

describe how pyroxene would under go oxidation?

- pyroxene dissolves releasing silica and ferrous iron to solution - ferrous iron is oxidized, forming FERRIC iron which than combines with water and precipitates as a solid into an iron oxide such as hematite

how do soils influence weathering

- retain water required for weathering - soil water often exhibits HIGHER co2 content than rainwater, therefore making it more acidic than rainwater

mining and mineral processing produces large volumes of mine wastes - waste rock is removed because _________ - tailings are produced by ?

- waste rock is removed because it contains small amount of economic materials - tailings (by products) are produced by separation of economic from non economic (gangue) minerals

describe ice wedging - important in ____ climates and ____ regions

- water enters cracks in rock and expands during freezing - outward force can wedge open cracks and split rocks - ice is less dense than water - freezing causes expansion - temperate climates and mountainous regions

describe exofoliation - example

- when rocks form underground and they reach the surface the low pressure causes them to expand and crack (pressure release during exhumation), could also be due to expansion and contraction during temperature change -along with cracking there is detached large flat or curved sheets of rock - contribution to jointing of granitic rock adjacent to the coquihalla highway near Hope BC

describe weathering in hot and arid environments

-salts accumulate at the surface to evaporation - frost, abrasion, and slaking break the rock into sand or gravel - wind blows smaller particles away

which minerals in granite are most susceptible to weathering?

1. feldspar, biotite, magnetite, quartz present ' 2. cracks form along crystal boundaries, everything starts to decay except for quartz (clays form) 3. as the decay progresses and as cracks open, the rock weakens and disintegrates

what affect does weathering have on C02 in the atmosphere?

It decreases the amount of CO2 in the atm

whats the major portion of soils ? 45%

MINERALS

is pH of rainwater the same everywhere on earth? what is it?

actually only 5 and no

chemical weathering - reactions of minerals with _____ and ______ - may promote mineral _____ and/or formation of ___ _____

air and water dissolution and or formation of new minerals

define dissolution rate

amount of mineral that dissolves in an unsaturated solution in a given time - less stable minerals tend to dissolve more quickly - composition and bonding influence dissolution

what happens when quartz is hydrolyzed?

basically just produces smaller quartz - sedimentary quartz

_____ produced during chemical weathering is transported and stored _______

bicarbonate, oceans also forms carbonate minerals (calcite)

soil formation influenced by:

biological processes nature of parent rock climate topography time

what is hydrolysis?

chemical reaction between mineral and acidic water - acid rain (carbonic acid)

what accounts for observed differences in mineral weathering rates ?

chemical stability

three sizes of fragments rank them smallest to largest, what does the size of fragements determine ?

clay sized > silt sized > sand sized size of fragments determines the texture

last group of silicates to break down during weathering ?

clays - kaolinite quartz ?

all rocks exposed to ___ ___ undergo weathering

climate system

Soils form the interface between ____ and the ____ ___ ___

climate system and plate tectonic system

carbon dioxide from the atmosphere is ______ during chemical weathering

consumed

dark soil is rich in: light soil is rich in:

dark - organic matter light - lacks organic matter

describe how karst topography comes about?

dissolution by carbonic acid dissolves the mineral calcite, which is the main constituent of limestone widespread dissolution of carbonate rock leads to the development of karst topography

Dissolution of calcite does what ?

dissolved CaCO3 and the product is calcite travertine

give an example of a economic and non economic sulfide minerals

ec - chalcopyrite, or galena )with Pb non-ec - pyrite

negative regions of water molecule attracts cations and this ?

enhances chemical weathering

soil erosion - significant ___ ___

environmental issue

soil erosion versus soil formation

erosion - losses amount to trillions of tons per year - 0.04 cm / year human activities accelerate the loss of soil formation - is almost always slower than soil erosion important factors: climate and time nature of the source rock

what dissolves faster, feldspar or quartz?

feldspar dissolves much quicker because there is some ionic bonding (2 cleavage planes at 90 degrees) quartz - only covalent bonding, no cleavage planes

the role of water: _____ is one of the many silicate minerals that are altered to form _____ minerals why do we care? (2)

feldspars one of several minerals that are altered to form clay minerals 1. feldspar is abundant in earths crust 2. it is a common weathering process common to other minerals

the role of oxygen - oxygen facilitates oxidative wreathing of minerals containing ____ ____ examples

ferrous iron Fe2+ iron rich silicates - pyroxene and olivine sulfide minerals - pyrite

define physical weathering

fragmentation of rock without chemical change

you can describe soils as ______ with ____, ___ and __

geosystem with inputs, outputs, and processes

in water: halites solubility? quartz solubility?

halites - higher sol quartz - lower sol

Oxidation of olivine does what ?

hematite is produced and it gives off H2CO3

minerals with _____ solubility are less stable and thus ____ susceptible to weathering

higher solubility, less stable, more susceptible to weathering

chemical weathering processes include : (3)

hydrolysis oxidation dissolution

how does weathering produce sedimentary rock ?

igneous, metamorphic, or sedimentary rock under go weathering to produce sediment which is subsequently transported, deposited, and undergoes lithification

in what conditions would you get little weathering

in arid climates

what happens when we dissolve carbon dioxide in water? decreasing or increasing pH accelerates weathering ?

it produces carbonic acid - weak acid therefore lowering pH and increasing the rate of weathering

mass wasting erosion

landslides - debris flows - mudflows

hydrolysis feldspar weathering illustrates three main effects of chemical weathering on silicates

leeching - cations and silica are dissolved away hydration - water is added to minerals neutralization - solutions are made less acidic (carbonic acid)

tailings vs waste rock ..

like waste rock tailings have no economic value, large volumes, high surface area BUT they have high sulfide-mineral content the difference is that waste rock never had the potential to be of any economic value whereas tailings are the result of the valuable component being separated away from the silica and this is what is left over

cold environment

mechanical breakdown (ice wedging) is the major weathering processes

waste rock - ____ - economic - ____ volumes - high _____ _____ - ____ - ____ sulfide mineral content

non-eco high high SA low to moderate sulfide mineral content

list the stability of minerals from olivine > quartz

olivine > pyroxene > ca-plagioclase feldspar > biotite > orthoclase feldspar (K) > quartz

____ and other sulfide minerals are unstable in the presence of ____ and ____

oxygen and water

mine waste weathering - sulfide minerals weather in the presence of _______ and ________ -generate _____ - release ____ and metals

oxygen and water generate acid and release sulfate and metals

what three things influence solubility ?

pH, temp, pressure

finer vs ped soils which resist erosion which may become loess

ped - resist erosion loess - may become loess ( formed by dust blown fine particles )

structure: tendency to form ____

peds

where does physical weathering dominate? where does chemical weathering dominate?

physical - regions of low temperature, dry climate (low rainfall) chemical - regions of high temp and high rainfall

abrasion by glaciers - ______ weathering due to ____ between ____ and particles transported by the glacier - material is removed from rocks by particles in the glacier - generates __________ __________

physical weathering due to friction between rock and particles transported by glaciers - generates new particles

weathering is the result of ______, _______ and _____ processes

physical, biological and chemical processes

physical weathering - due to _____ release, ab_______, freeze-____, ______ action, growth of _______ crystals, or other physical means - aided by ______, rock ________ and other types of fractures

pressure release, abrasion, freeze-thaw, hydraulic action (ex.waves), growth of salt crystals, or other physical means aided by bedding, rock joints, and other types of fractures

what happens when orthoclase feldspar undergoes hydrolysis

produces (dissolved) K+. and silicate SiO2 and turns it into kaolinite clay

products of weathering leads to ?

production of soils

weathering modifies ____ and the _______ within them

rock and the minerals within them

define ventifact

rocks that have been abraded, pitched, etched, grooved by wind driven particles

growth of salt crystals - ____ water seeps into ______ rock and then _______, causing interstitial growth of _____ _____ which pry the rock ______ or ______ apart

saline water seeps into the permeable rock and then evaporates causing interstitial growth of salt crystals which pry the rock grains or crystals apart

weathering produces _______ which is subsequently _____ by ______ and transported elsewhere

sediment, removed by erosion and transported elsewhere

what is the most specific Canadian soil classification, least?

series is most specific - pedon features order - dominant soil forming process is least specific (order, great group-strength of soil forming process, subgroup-kind and arrangement of horizons, family-parent material characteristics , series)

outputs :

soil profiles with distinct layering and structure - leaching, wind, water erosion

Where is clay abundant?

soils and sediments

______ ore deposits are a main source of metals

sulfide

what kind of slope might ice wedging produce?

talus slope

define chemical stability and what it is determined by ?

tendency for a mineral to retain its composition during weathering - solubility - dissolution rate

How exactly does carbonic acid hydrolyze feldspar?

the carbonic acid splits into hydrogen atom and carbonate and the carbonate react with the feldspar weathering it to clay! it than releases bicarbonate ions and potassium ions keep in mind that this is both the work of CO2 and H20 which combine to form carbonic acid

are framework silicates more or less susceptible to weathering than olivine for example ?

they are less

what mineral are microbes likely to oxidize?

they are likely to oxidize pyrite (FeS2)

true or false: oxygen and carbon dioxide do not have a substantial influence on weathering reactions

this is false. they do

describe the processes of soil - transformations: - translocation: factors influencing soil information:

transformations: physical and or chemical changes over time translocations: horizontal and lateral movements of material factors: biological processes: plants, animals, microbes, humans nature of parent rock climate: percip and temp topography: slope and aspect (which direction a slope faces) time: duration of interaction of these factors

True or false: concentration of CO2 in the atm is relatively small

true

sulfide ore deposits contain both economic and non economic minerals, true or false?

true

true or false: any rock exposed at earths surface can undergo weathering?

true

true or false: stability is dependent on environmental conditions

true

true or false: variations in atmospheric carbon dioxide concentrations impact weathering rates?

true

true or false: weathering enables growth of new minerals through crystallization

true

describe fluvial erosion Fluvial processes include the motion of sediment and erosion or deposition on the river bed. Erosion by moving water can happen in two ways. Firstly, the movement of water across the bed exerts a shear stress directly onto the bed.

water - suspension: perpetual state of movement in water without touching floor - bed load: skipping and hopping temp. water column - saltation : particle bounce into water column

rocks tend to fracture along natural zones of _______ examples?

weakness - bedding planes in shale - foliation plates in slate - jointing in basalt

what three things are inputs for soil

weathered rock , organisms, dust

what are soils comprised of ?

weathering products, organic matter, water and gases - large diversity of micro and macro organisms

eolian erosion

wind

what is the difference between open pit and underground, is mining considered weathering?

yeah it is I think.

does weathering contribute to soil production?

yes