Physical and chemical weather

Fig. 9-8 Histogram of dissolved solids of samples from the Orinoco and Amazon River basins and corresponding denudation rates for morpho-tectonic regions in the humid tropics of South America (Stal-lard, 1985). The approximate denudation scale is calculated as the product of dissolved solids concentrations, mean armual runoff (1 m/yr), and a correction factor to account for large ratios of suspended load in rivers that drain mountain belts and for the greater than average annual precipitation in the lowlands close to the equator. The correction factor was treated as a linear function of dissolved solids and ranged from 2 for the most dilute rivers (dissolved solids less than lOmg/L) to 4 for the most concentrated rivers (dissolved solids more than 1000 mg/L). Bedrock density is assumed to be 2.65 g/cm. (Reproduced with permission from R. F. Stallard (1988). Weathering and erosion in the humid tropics. In A. Lerman and M. Meybeck, Physical and Chemical Weathering in Geochemical Cycles," pp. 225-246, Kluwer Academic Publishers, Dordrecht, The Netherlands.)...

Provide some simple reasons for the rules of thumb for physical and chemical weathering given in Section 9.2.1. 

What is the distinction between physical and chemical weathering ... 

Stallard, R. F. (1988). Weathering and erosion in the humid tropics. In "Physical and Chemical Weathering in Geochemical Cycles" (A. Lerman and M. Meybeck, eds), pp. 225-246. Kluwer Academic Publishers, Dordrecht, Holland, NATO ASI Series C Mathematical and Physical Sciences 251. 

Meybeck, M. 1988. How to establish and use world budgets of riverine materials. In Physical and Chemical Weathering in Geochemical Cycles (A. Lerman and M. Meybeck, Eds.), pp. 247-272. Kluwer Academic, Dordrecht. 

Examples 5.1, 5.2 and 5.3 deal with different aspects of physical and chemical weathering. 

The final case of surficial ore genesis dealt with here involves the transport of physically disaggregated residuum from physically and chemically weathered materials by wind and water, resulting in placers, mineral deposits formed at the Earth s surface by mechanical... 

A important relationship between physical and chemical weathering was proposed by Carson and Kirby (1972) and Stallard and Edmond (1983), who differentiated mineral selectivity in... 

Picouet C., Dupre B., Orange D., and Valladon M. (2001) Major and trace element geochemistry of the upper Niger (Mali) physical and chemical weathering rates and CO2 consumption. Chem. Geol. 93-124. 

Discuss the nature of physical and chemical weathering in soil and soil forming geological rocks. Make some connections with biogeochemical turnover of elements in any simulated ecosystem. 

Lerman, A. (1988), Weathering Rates and Major Transport Processes, in A. Ixrman and M. Meybeck, Eds., Physical and Chemical Weathering in Geochemical i ycles, Khiwor Academic Publishers, Dordrecht, Netherlands, pp. I 10. 

Quaternary glacial-interglacial alternations caused terrestrial alternation of physical and chemical weathering processes, and this was reflected in... 

In the process of soil formation, these rocks undergo both physical and chemical weathering, which occurs most rapidly at or near the surface and progressively less at lower levels. The rate of weathering depends chiefly on the climate, mostly on rainfall and temperature, and on the activity of living organisms. The relief can also be a factor of considerable importance where areas of marked differences in elevation are compared under similar climatic conditions. 

Figure 2.66 Physical and chemical weathering vs. climate conditions. Chemical desalination grows as temperature and humidity increase.

Kim, S. and Park, H. 2003. The relationship between physical and chemical weathering indices of granites around Seoul, Korea. Bulletin of Engineering Geology and the Environment, 62, 207-212. 

Kandic Composed of low activity clays, which are accumulated at its upper boundary. Clay skins may or may not be present. It is considered that clay translocation is involved in the process of kandic formation, however, clay skins maybe subsequentlz disrupted or destroyed by physical and chemical weathering, or they may have formed in situ. Requirements Within a distance of < 15 cm at its upper boundary the clay content increases by > 1.2 times Abrupt or clear textural boundary to the upper horizon At pH 7 low-activity clays with CEC of <16 cmol/kg and ECEC (effective CEC) of <12 cmol/kg. 

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