1. Weathering

2. Transportation

3. Corrasion

soil and weathered rock

(collectively called regolith)

1. producing smaller chunks (now transportable)

2. creating ways for water to move through rock

3. produces more surface area (can help chem weathering later)

1. frost cracking

2. oxidation/hydration cracking

3. joints

4. salt cracking

5. root wedging

this occurs when water freezes in small pores but a thin layer of water remains on the surface of the ice below the freezing point. this thin film of water flows, following pressure gradients, and moves toward the ice layer because it is a lower pressure. the water formes small layers (lenses) of ice (even against the pull of gravity) and these ice lenses create pressure and cause the rock to break.

the cracking continues after freezing because of that thin layer of water that doesn't freeze but builds an ice layer.

this happens best in rock under a soil layer in a cold environment where seasonal ground freezing is likely

many minerals expand when they oxidize and/or react with water

ex: biotite (mos common mineral w/ this behavior, expands up to 40% when wet)

this expansion works in juncture w/ chem weathering which transforms the mineral (ex biotite into iron oxide and hydroxybiotite and ultimately to vermiculite) once transformed, it reacts with water and expands, pushing on the surrounding rock and leading to small fractures

these are fractures in a rock that do not displace the rock around the fracture

they occur in sets with rock being fractured in a series of concentric or parallel fractures with some spacing

this is a type of joint where fractures form parallel to the ground surface forming giant "onion skin" layers of rock

it occurs in rock that is not already cut by vertical joings

it is normally found in large, flaw free rocks

it is a response to unloading (the removal of rock mass from the surface by erosion) in rocks that are under a lateral compression

unloading reduces pressure which allow vertical expansion and formation of surface parallel joints

this is when, in arid climates, salt crystals grown in microcracks in the rock, splitting the rock apart

this happens b/c salt from dissolution of minerals in rock or from rainstorms is left behind when water evaporates and forms salt crystals

it is the alteration of minerals and rocks at earth surface conditions

it happens because many minerals ar chemically unstable at conditions on earth's surface

1. it releases nutriens such as Ca, K and P from rocks

2. it weakens rock (clay minerals are weaker than other silicate minerals)

3. it delivers salts to the ocean (all the dissolved ions are carried by rivers to the sea)

4. it produces clays, an important constituent of soils

5. it consumes CO2 from the atmosphere

this is a part of chemical where products are dissolved

it happens when a mineral breaks apart into constituent ions or molecules and these go into water

after dissolution is complete, no solid material left, water now carries dissolved salts

most dissolved species = ions

the reaction of halitite with water that produces a sodium ion, a chloride ion, and water

NaCl + H₂O --> Na⁺ + Cl^- + H₂

it dissolves congruently especially when carbonic acid (CO2 gas dissolved in water) is present

rain is naturally slightly acidic from carbonic acid (H₂CO₃)

Calcite in rainwater dissolves forming bicarbonate and a calcium cation

CaCO₃ (calcite) + H₂CO₃ (carbonic acid) --> Ca²⁺ + 2HCO₃^- (bicarbonate)

this is when products include a new solid material as well as a dissolved species

most silicate minerals weather this way, b/c silicate is the most abundant material on crust, this is the most common type of weathering

it differs from congruent dissolution b/c a new mineral is formed in the process + a dissolved species

ex: mineral A + carbonic acid (H₂CO₃) --> mineral B + dissolved silica

again, acids speed up these reactions

a reaction with oxygen

involves the transfer of electrons between atoms, one atom gives up an electron (becoming oxidized) anoher atom takes an electron (becoming reduced)

oxygen is very electronegative so it's a strong oxidant

manganese and iron are commonly involved in these weathering reactions

an example is rusting of iron: 2Fe²⁺ + (3/2)O₂ --> Fe₂O₃ (iron gas + oxygen gas yields hematite (aka iron oxide or rust)

these reactions form oxide minerals and impart red-yellow-brown hues to soils b/c iron oxides are highly colored

rank in order of weathering from slowest to fastest:

Calcite, Olivine, Amphibloe, Pyroxene, Mica, Feldspar, Quarts

the reaction of calcite with carbonic acid

CaCO₃ + H₂CO₃ --> Ca²⁺ + 2HCO₃^-

rusting of iron

2Fe²⁺ + (3/2)O₂ --> Fe₂O₃

they are sheet slates (like micas) but are softer and have fewer cations in their structure

they are stable at earth surface conditions

most commonly have microscopic crystals

an example is Kalonite (aluminum-silicate hydroxite) - used to make pporcelan and to make magazene pages glossy

this cyle moves carbon between the atmosphere and silicate rocks

the process starts w/ dissolved products from weathering carried to the ocean where plankton use the dissolved salts to make their shells. the reaction of forming the shells is the revers of the congruent dissolution of calcite. when the plankton die, the shells fall the the sea floor, accumulate, and form new limestone rock

the net effect of calcium silicate weathering and carbonate precipitation is calcium silicate mineral + CO2 yielding limestone and silica

since CO2 comes from the atmosphere, these processes (weathering and shell formation) remove CO2 from the atmosphere and deposit it as limestone on the seafloor

over geologic timescales of hundreds of thousands of years, weathering plays an important role in controlling atmospheric CO2 concentrations (much more than biomass does in terms of human lifetimes etc)

a disaggregated and altered rock material mixed with organic matter

often has visible horizontal layers and can support vegetation

anything so named by a pedologist

most complex biomaterial on earh

when material is moved from one place to another witin a soil

movement can be in a solution (products of dissolultion) followed by precipitation (formation of a new mineral) or the movement can be as particulates moving under gravity carried downward by soil water

loss of material by erosion or leaching (in solution)

they differ from vertical transfers in that the material is moved out of the soil column all together

the smallest volume of soil that contains all the lateral variations within the horizons of a particular soil

usually 1-10m² in lateral extent

they extend vertically to the base of teh soil

the first step in soil description is to identify this for that soil

layers of soil defined by depth, organic matter content, mineraology, and structure of the layer

they are usually approximately parallel to the surface

have distinctive characteristics compared to adjacent horizons, often visually distinct

form over time in response to geological, biological, and chmical processes

not all horizons are in all locations

labeled O, A, E, B, C, R

from top to bottom: O, A, E, B, C, R

think Organic, A (#1) top soil, eluvial (emigrated), Below (a, e, and o), C only slightly altered so think Cracked bedrock, R is hard bedrock so think Rock hard

O for organic

the surface accumulation of organic matter in any state of decomposition

decomposed organic matter = humus

"top soil"

this is a mineral horizon at the surface or below the O horizon

it contains more organic matter than underlying horizons

humified organic matter is intimately mixed with the mineral material, giving it dark color and making it nutrient rich

Eluvial horizon

eluvial means material has been removed (think emigrated) from the horizon

most commonly made of clay, iron, and aluminum that are lost

loss of these materials leaves a sandy, light colored horizon

Below A, E, or O

commonly illuvial horizons, meaning marked by illuviation (accumulation) of material from above. to remember eluvial and illuvial, think emigrant and immigrant

the materials that accumulate in this layer include clay, iron, aluminum, carbonates, or humus. there is little evidence of original rock structure or sediment layers left in this horizon

"cracked"

only slightly altered by pedogenic processes; if produced from bedrock, the C horizon exludes hard bedrock

color depends on minerals present, the presence or absence of iron oxides (a little iron goes a long way to color a soil), the organic matter content, and the extent of leaching. soil scientists use a soil chart, the Munsell soil color chart, to uniformly describe soil colors

1. hue - the place on the color wheel

2. value - how light or dark

3. chroma - how intense or saturated the color is

it is defined by the properties of different grain sizes present

grain sizes can be measured and are grouped into size classes

the three size classes important in soils are: clay, silt, and sand

it involves grains up to 4 micrometers (microns) in size

there are 1000 microns in 1mm so 4 microns is teh same as 0.004 mm. clay size particles feel smooth and creamy, or sticky between your fingers

do not confuse clay size particles, you can also find other minerals in this size range

this includes grains between 4 and 62 microns (0.004-0.062 mm)

this size material feels gritty between your teeth but floury in your fingers

wind blown dust is usually this size

this includes grains between 62 microns and 2 mm (0.062 - 2mm)

it feels gritty no matter how you test it

vertical columns that may be many cm long

often found in B horizons

the volume of the voids (holes) in a soil/rock divided by the total volume of a soil sample

expressed as a percentage

when a soil was drenched in water and after about two days all of the gravitational water is largely gone - this is the remaining water cntent in the soil

when the soil is here, water and air are in the soil and water is freely available to plants

a measure of the capacity of a soil sample to hold cations on exchange sites between clay, minerals, organic matter and cations in water/soil

clay = neg charge b/c of deficits in ineral lattice

organic matter = neg charge b/c of functional groups

these attract cations

related to soil fertility bc cations like Ca²⁺ and K⁺ are essential to plant life

soils with higher this are more fertile

since exchange sites are found on clays and organic matter, soils w/ higher clay and organic matter tend to have higher CEC and better fertility

the measure of how much of the CEC is actually occupied by useful base cations

the useful base cations are Ca²⁺, Mg^2+, Na⁺, and K⁺

carbon is exchanged between the atmosphere and carbonate rocks

most of the carbon in this cycle is in the rocks (40,000,000Gt C vs 720Gt C in Atmosphere)

carbon goes from the atmosphere to the rocks through weathering of silicate rocks and is returned to the atmosphere through metamorphism and volcanism

carbon is exchanged between the atmosphere, biomass, soil organic matter, and methane

most C is in the soil organic matter (1600 Gt C), the second most is in the atmosphere (760 Gt C) and the third most is in the biomass (600 Gt C)

it looks like:

atmosphere -> (photosynthesis) biomass -> (respiration) back to atmosphere AND -> (decompositon) back to atmosphere AND -> (death) soil organic matter aka humus -> (decomposition) back to atmosphere AND -> (fermentation) to teh atmosphere OR to methane -> (atmospheric circulation) to the atmosphere

the classes are falls (rock fall), slides (slump or translational slide), and flows (earthflows, mudflows, debris flows)

they are organized based on speed, material, and type of movement

it is when the material slides along a curved failure plane that looks like someone used a giant ice-cream scoop on the hillside

the parts are scarp, failure surface, and toe

gophers and other fossorial rodents that throw soil on groudsurface, typically they throw it downslope and once the material is on the surface it ravels and is washed away by rain downslope

(ravel is dry, downward rolling and fall of material on a hillslope)

D=M/V

or F = MA

or W = MG

they can be decreased by taking away vegetation but increased by adding vegetation

they can be increased by a small amount of H2O (increase cohesion) but once the water is saturated it decreases them b/c it makes them unstable

water can also add to the mass which increases the driving force, overcoming this force

a measure of how strongly materials stick together or are held in a coherent mass

includes the effects on surface tension in a partially wetted soil

includes knitting together of soil by roots and trees

the resistance of a soil mass to sliding

inversely related to the amount of mositure in teh soil

greater in sands

a specially designed deep glass-walled flume used to study subaqueous debris flows

river or tap water can be used