l>CHAPTER 5: WEATHERING, EROSION, and also SOILWEATHERING--the disintegration and also decomposition of absent at ornear surface.MASS WASTING--the transport of rock product downslope under theinfluence that gravity.EROSION--the incorporation and transportation of product by amobile agent: WATER, WIND, or ICE.Weathering drops into two catagories: mechanical WEATHERING (physical weathering process)andCHEMICAL WEATHERING.

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MECHANICAL WEATHERING - "making huge pieces into smallerpieces"

Types of mechanical Weathering:FROST WEDGING--ice forms in cracks, splits rocks. Widening ice at a temperature that 22 that ( -7.6oC) deserve to exert a pressure of 4.3 million pounds per square foot (2,100 kg/cm2) (atmospheric press at sealevel ~ 15 lb/ft2)UNLOADING--removal of rock overburden reasons rocks the wereunder push toexpand, producing joints, cracks in a rockthat have not had appreciable motion of rock along the cracks. The process of expansion by unloading leader to "sheeting" that creates exfoliationdomes
(such together in Yosemite nationwide Park, CA). Half Dome, Exfoliation Dome, Yosemite, CASheeting in mines because of the relax of pressure, through tunneling or quarrying,can reason rock top top the political parties of column to dangerously explode off the wall surfaces in rock blasts.THERMAL EXPANSION--daily heating cycle reasons 30o C variation;this reasons expansion push on the surface ar of rocks the createsfractures.ORGANIC ACTIVITY--plants (roots), burrowing animals, humans.Roots broaden after a rainstorm. Salt wedging--precipitating salts create a push as the salt crystals form. This forcecan rest rocks apart. This is most important near the coasts where s spray is constantlybeing deposit on rock surfaces outcomes OF mechanical WEATHERING--Mechanical weathering acts to increase the surface ar area availableto chemical attach. Forexample, a fresh block of granite with a volume the 1 cubic meterhas 6 sides through a full of6 square meter of surface area. The surface ar area in ~ a cubicmeter that sand approaches asquare kilometer! for each cubic meter the sand ~ above the beachabout 10 cubic meter of clayare deposited offshore. Clay particles room "flat"- comparable tochips the mica, and also have as much as 100times the surface ar area as an equal volume that sand. The greater the surface area, the higher the area come be operated on by chemical weathering.

CHEMICAL WEATHERING--involves chemical transformation into 1or an ext new materials.

H2O + CO2 = H2CO3 (carbonic acid) from atmosphere and also plantacids dissolve mostrocks with time. H2CO3 + CaCO3 (calcite) = Ca+2 + HCO3-, a reversibleprocess (land and also oceans).Calcite is the main mineral in limestone. Calcite likewise acts aa cement in sediments toform sedimentary rocks.Quartz (SiO2 ) dissolves and reprecipitates together silica, whichacts as a cement in sedimentsto form sedimentary rocks.Feldspar weathers to end up being clay (reversible undermetamorphic conditions).Mafic Minerals come to be clay, silica, and also iron oxide minerals(limonite/hematite).Cations (such as K+, Na+, Ca++ and also anions (such as Cl-,HSO4- ,HCO3-) remain insolution and add to the saltiness of the ocean, precipitate assalts, or are incorporated intoclays in sediments.

WEATHERING FEATURES

absent exposures, such together on cliffs or barren hilltops, havecharacteristic appearances early toSpheroidal Weathering (the "rounding of stormy edges") that occurs since chemical attackis much more effective top top corners (it comes from 3 sides of the corner) contrasted to deals with (chemical strike is only from one direction) andDifferential Weathering (some rocks and also rock layers resist erosion far better thanothers) producing a stormy weathered surface. Hoodoos and also arches space the an outcome ofdifferential erosion and the beauty, beauty of these features has motivated us to develop twonational parks Arches and Bryce Canyon nationwide Parks, both in Utah.As chemical and also mechanical weathering proceed, absent materialaccumulates as aREGOLITH class of rock and also mineral fragments produced byweathering. If water isavailable, plant and also animal activity affect the material, anddead organic issue accumulates.This results in the development OF SOIL. SOIL--mineral matter (~45%), HUMUS--organic issue (~5%), air &water (~50%).CONTROLS OF soil FORMATIONPARENT MATERIAL--the initial mineral matter deserve to be either:RESIDUAL(regolith the accumulates "in place") or TRANSPORTED mineralmaterial through water, wind,or ice.TIME--important to all geologic processes; longerexposure = an ext weathering.CLIMATE--water and also temperature influence weathering processes.Hot & humid climatesproduce deep weathering soils lacking important nutrients. Cold &dry climates outcomes in veryslow weathering which boosts chances that wind erosion beforesoil have the right to form.PLANTS & ANIMALS: microscopic organisms do many of the work;the acculation oforganic mater develops HUMUS; roots, worms, rodents, and also insectsrework the regolith andhumus to form soil. Steep - soils have tendency to be thickest on level surfaces (due tomass wasting & erosion). Sunny slopes often tend to be warmer and dry faster.SOIL PROFILEO horizon--"fresh" organic matter that accumulates onthe soil surface.

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A horizon--consists of combined organic and also rockfragments: water washesout fines (by a process called ELUVIATION); mineral nutrientsdissolved away by processcalled LEACHING.B horizon--zone the "accumulation" of fines; develops a"hardpan"C horizon--(below "solum" or true soil) is a zone ofweathering bedrock above the actual unweathered bedrock--still considered aregolithTHREE basic KINDS that SOILSPEDALFER--soils wealthy in aluminum-rich clays and iron; midlattitudes, through annualprecipitation the at least ~25 inches (East coast region).PEDOCAL--soils in dry areas (due to high evaporationrates). Enriched v calcium carbonate, caliche (Western joined States).LATERITIC--soils in wet, much more tropical climates. Allcalcite and silica is leached indigenous the soil, leave red (iron) and also aluminum (aluminum can be enriched sufficient to formthe ore mineral Bauxite indigenous which we achieve aluminum metal) (South).Click here toreturn come the course Website