Limestone areas

Stalactites and stalagmites are found in underground caverns in limestone areas. They are formed from the slow decomposition of calcium or magnesium hydrogencarbonates in water (Figure 11.34). 

Iron film Lithobiontic coatings Nitrate crust Composed primarily of iron oxides or oxyhydroxides Organic remains form the rock coating, for example lichens, moss, fungi, cyanobacteria, algae Potassium and calcium nitrate coatings on rocks, often in caves and rock shelters in limestone areas... 

This reaction is responsible for formation, over thousands of years, of caves and gorges in limestone areas, as CO2-laden rainwater very slowly dissolves the rock. The process is slow because the equilibrium constant is small. This constant can be... 

The ability of forests to withstand acid rain depends on the capacity of the soil to neutralize the inputting acidity. This is largely determined by local geology, in much the same way that it affects the acidification of lakes. Acidification is mainly a problem in areas where the underlying rocks provide poor buffering capacity. Rocks such as granite offer little buffering protection. Chalk and limestone neutralize added acid, and so soils, lakes and streams in limestone areas are fairly insensitive to acidic precipitation. 

Write two reactions that explain why lakes in limestone areas are capable of resisting pH decreases due to acid rain. 

In a limestone area, go to any hill where a road is cut through and get a 2 A gallon bucket full of what you consider to be a representative sample of the layers of limestone present. The size of the rocks should be no larger than 2.5 inches in diameter. These will be ground in a jaw crusher to 1/4 inches in diameter and then finally to 100 mesh in a disc pulverizer. Cone and quarter the sample to reduce it to about 15 grams, which you will place in a weighing bottle. Place... 

Figure 17. Typical water, sediment and moss compositions from the Magliasina river (major river of the Malcantone) compared to the Breggia river (Ticino, Switzerland), which lies in a limestone area with low natural metal contents. Data from Martini and Fillet (1996).

Chan, S.F. Hong, L.P. 1985. Pile foundations in limestone areas in Malaysia. Foundation problems in limestone areas in Malaysia. The Institution of Engineers Malaysia. Malaysia Kuala Lumpur. 

Ting, W.H. 1985. Foundation in limestone areas of Malaysia. Special Lecture, Proc. SthS.E. Asian Geotechnical Conf, Kuala Lumpur, March 1985, 2 124-136. 

The dissolution of limestone is a very slow process. For instance, Kennard and Knill (1968) quoted mean rates of surface lowering of limestone areas in the British Isles that ranged from 0.041 to 0.099 mm annually, and Sowers (1996) suggested rates of 0.025 to 0.040 mm a for the eastern United States. More recently, Trudgill and Viles (1998) quoted calculated erosion rates of calcite of 0.06 to 0.11 mm a- at pH 5.5, and 2.18 to 2.69 mm a at pH 4.0. Nevertheless, solution may be accelerated by man-made changes in the groundwater conditions or by a change in the character of the surface water that drains into limestone. 

Dry valleys are characteristic of the limestone and chalk downland. The few rivers rise from underground streams and the deliberate flooding of water meadows in the river valleys used to be a common practice. Watercress beds flourish along some chalk streams. The farms and fields on this type of land are usually large, especially on the thinner soils. There are very few hedges and the trees are mainly beech and conifers. Walls of local stone form the field boundaries in some limestone areas. 

The diagram on the last page shows an underground cavern containing stalactites and stalagmites. Caverns like this are often found in limestone areas. 

In areas where the degree of contamination of soils is exceptional, for example, in mineralised areas or in the vicinity of lead smelters, entry of lead into food chains can occur. Davies and Roberts [362] have reported undesirably high levels of lead in radishes grown in soils in a mineralised limestone area in north Wales which had been contaminated by lead mining operations. 

Water and nutrient relations differ markedly at the base, slope and tops of Mogotes, determining changes in density and species composition of the woody vegetation (Weaver, 1979 Chinea, 1980 Serrano et al., 1983 Alvarez Ruiz et al., 1997). The limestone areas in Puerto Rico have been divided into northern, southern and dispersed limestone areas (Lugo et al., 2001). Since little is... 

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