Rocks weathering

Thermal expansion induced by insolation may be important 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. Each type of mineral in a rock has a different coefficient of thermal expansion. Consequently, when a rock is heated or cooled, its minerals differentially expand and contract, thereby inducing stresses and strains in the rock and causing fractures. Ollier (1969) discussed examples of rock weathering due to insolation. Fire can develop temperatures far in excess of insolation and be quite effective in fracturing rocks (Black-welder, 1927). 

Goudie, A., Cooke, R., and Evans, I. (1970). Experimental investigation of rock weathering by salts. Area 4,42-H8. 

Why are the oceans so depleted in these trace metals Certainly it is not for the lack of availability from rock weathering or because of constraints imposed by the solubility of any unique compound of these elements. The reason must lie in the dynamics of the system of delivery of the metals to the oceans and their subsequent behavior in an ocean that cannot be simulated by simple in vitro experiments involving homogeneous reaction kinetics. 

Surface ions are thus expected to substantially contribute to the polarization force at low frequencies. Also, one expects different ions to have different solvation properties and mobility. These phenomena can be explored by SPFM. They are important in surface reactions, ionic exchange processes between surface and bulk ions, rock weathering, ion sequestration, and other enviromnental problems. 

Smectite is the first secondary mineral to form upon rock weathering in the semi-arid to sub-humid tropics. Smectite clay retains most of the ions, notably Ca2+ and Mg2+, released from weathering primary silicates. Iron, present as Fe2+ in primary minerals, is preserved in the smectite crystal lattice as Fe3+. The smectites become unstable as weathering proceeds and basic cations and silica are removed by leaching. Fe3+-compounds however remain in the soil, lending it a reddish color aluminum is retained in kaolinite and A1-oxides. Leached soil components accumulate at poorly drained, lower terrain positions where they precipitate and form new smectitic clays that remain stable as long as the pH is above neutral. Additional circumstances for the dominance of clays are ... 

Caldeira, K., Forests, climate, and silicate rock weathering, /. Geochem. Exploration, 88(1-3), 419 (Special Issue), 2006. 

Lovering, T. S., Significance of accumulator plants in rock weathering, Geol. Soc. America Bull., 70, 781-800 (1959). 

Liu, Z. Zhao, J. 2000. Contribution of carbonate rock weathering to the atmospheric C02 sink. Environmental Geology, 39, 1053-1058. 

Calcium also has isotopic variations stemming from the radioactive decay of " K to " Ca. These variations can be used for geochronology and may also be useful for studies of rock weathering, soil formation, magma genesis, diagenesis, and metamorphism. 

The water composition of alpine rivers is strongly influenced by natural diffuse inputs originating from rock weathering. Weathering processes are defined as the alteration of rocks in the top crust of the earth it is mainly an interaction of water with rocks [9, 10]. Water can act through physical and chemical processes. 

Rocket propulsion oxidizers, 18 384-385 Rocks, weathering of, radiation and, 3 299 Rocksalt, crystal structure of, 2 6, 29 Rock-salt-type alkali halide crystals, dissolution process, 39 411 19 alkali chlorides, 39 413, 416 alkali fluorides, 39 413-415... 

Gibbsite, a mineral more and more frequently identified in the early stages of rock weathering (especially magmatic rocks) is usually not important in river sediments but has been noted in small quantities over large areas in deep sea sediments (Griffin, et al., 1968 Biscay, 1965). 

In the discussion thus far, the application of systems with completely mobile components has been restricted to bed-rock weathering, sedimentation and free-flowing aquifer environments. As a first approximation in other geological situations, clay mineral suites can be adequately described using "inert" chemical components, i.e., those which are extensive variables of the system, and by using pressure-temperature as intensive variables. Hydrothermal alteration is, in contrast, an environment where many chemical components can be treated as being completely... 

The feldspars are aluminosilicates in which up to half the Si44 ions have been replaced by Al3+ ions. They are the most abundant silicate materials on Earth and are a major component of granite, a compressed mixture of mica, quartz, and feldspar (Fig. 14.45). When some of the cations between the crystal layers are washed away as these rocks weather, the structure crumbles to clay, one of the main inorganic components of soil. A typical feldspar has the formula KAlSi3Og. Its weathering by carbon dioxide and water can be described by the equation... 

Along the same lines, it was reported very recently from China [12] and India [13] that silicate and carbonate rock weathering in rivers gives rise to increased concentrations of dissolved ions such a Mg2+, Ca2+, Na2+, HCOJ, and CT, and that the C02 consumption of this should be taken into consideration as a sink for greenhouse gases. Further details on C02 reactions in aqueous solutions can be found elsewhere [6, 14]. 

---