Weathering physical

Physical phenomena bring about weathering as a result of temperature gradients, abrasion, erosion, mechanical forces, and other similar conditions. 

When rocks and minerals are stressed above their tensile strength they break. Commonly, rocks fracture along joints, fissures, or planes that have developed during cooling, tectonism, sedimentary processes, or along lines of weakness at the mineral grain boundaries. When buried rock masses are 

Thermal expansion induced by insolation may be of importance in desert areas where rocky outcrops and soil surfaces are barren. In a desert, daily temperature excursions are wide and rocks are heated and cooled rapidly. Minerals have different coefficients of thermal expansion. Consequently, when a rock is heated or cooled, its minerals differentially expand and contract inducing stresses 

In chemical weathering, proton donors or acids of organic and inorganic origin are involved, where the proton acceptors are the minerals in the soil (Stumm et al., 1985). In the last 100 years, anthropogenic pollution has contributed to the natural source of protons and this in turn has affected weathering rates and types. 

1 Water. Although the dissociation constant for water at 25° C is low (K = 10 ), water is so ubiquitous on this planet that, as Keller (1957) states, the reaction is inescapable. Even under continuous low temperatures and paucity of water, soil particles are surrounded by a liquid film of water and cannot escape hydrolysis reactions (Ugolini and Anderson, 1973). 

2 Carbonic acid. Water in equilibrium with atmospheric CO2 at 25° C has pH 5.65. Natural acidification of precipitation to pH less than 5.65 can occur in remote maritime air masses due to the presence of NH4HSO4 aerosols (Charlson and Rodhe, 1982). In the soil, the partial pressure of CO2 may be 10-100 and up to 400 times greater than that of the atmosphere (Holland, 1978). Given a CO2 pressure 10 or 100 times that of the atmosphere, pH values of 5.15 and 4.65, respectively, are expected. If additional sources of protons are introduced into the soUs, say, from organic or inorganic acids, the pH is depressed further. 

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Discuss how physical weathering operates in each of the following environments (1) sea shore, (2) hot desert, (3) temperate forest. 

Chemical weathering is more important in warm moist regions, whereas physical weathering is more important in cold dry areas. 

Contributions made by physical weathering are much greater in steep terrains (i.e., more primary minerals remain), and overall weathering rates are higher. 

In regions where the erosion regime is weathering limited, susceptibility of the bedrock to chemical and physical weathering controls erosion rates. This susceptibility relates directly to the chemical and physical properties of the rock. Susceptibility also depends on local climate. Moreover, weathering rates are affected by the... 

How might chemical and physical weathering have differed from today s world before the advent of rooted land plants What about before any land plants, assuming that there were once green films ... 

The result in terms of soil formation is a loss of soil. In desert areas covered by physically weathered shallow soils, deflation removes mainly the fine and medium-sized particles - clay and silt first, the somewhat coarser sand afterwards - and leaves behind a desert pavement, variously called reg (Sahara), serir (Libya) ox gibber plains (Australia). 

Geodynamic Condition Melioration caused swamping and clay soil settlement procedures are present here. Intensive physical weathering and depth erosion is present here Physical weathering is intensive, with landslides, talus and other gravitational developments Intensive weathering. With landslides, erosion and other developments can be observed here. 

Chemical weathering The conversion of minerals and other rock components into new, usually finer-grained materials through chemical reactions that typically involve water, natural acids, salts, carbon dioxide, and/or oxygen (compare with weathering and physical weathering). 

Demethylation The removal of a methyl (-CH3) from a chemical species (compare with methylation). Density The mass per unit volume of a substance. It s often measured in grams per cubic centimeter. Detrital Refers to loose rock and sediments produced by physical weathering. 

Physical weathering The mechanical breakdown of rocks into smaller fragments, which then contribute to the formation of soils and sediments (compare with chemical weathering and weathering). 

Weathering The physical or chemical conversion of surface rocks into sediments, soils, and dissolved and suspended materials in water through exposure of the rocks to liquid water, oxygen, carbon dioxide, wind, acids, salts, ice, biological activity, temperature fluctuations, and/or other factors at and near the Earth s surface (compare with chemical and physical weathering). 

Sand a course granular mineral mainly comprising quartz grains that is derived from the chemical and physical weathering of rocks rich in quartz, notably sandstone and granite. 

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