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Rocks can be broken into smaller pieces by a natural process known as weathering. Weathering refers to the chemical alteration and physical disintegration of rocks by the actions of air, water, and organisms. Two principal types of weathering are chemical weathering and biological weathering.
国葬是什么意思瓶子用英语怎么说The minerals that rocks are made of are subject to alteration by chemical weathering. Some minerals, such as quartz, resist this alteration quite successfully, but others, such as the calcium carbonate of limestone, dissolve easily. In any rock made up of a combination of minerals, the chemical breakdown of one t of mineral grains leads to the disintegration of the whole mass. In granite(made chiefly of the minerals quartz and feldspar), the quartz resists chemical decay much more effectively than does the feldspar, which is chemically more reactive and weathers to become clay Often granite surfaces are heavily pitted (marked with many small holes or depressions). In such cas, the feldspar grains are likely to have been weathered to clay and blown or washed away. The quartz grains still re
main, but they may eventually be looned too. So even rock as hard as granite cannot withstand the weathering process forever. warble
Three kinds of mineral alteration dominate in chemical weathering: hydrolysis, oxidation, and carbonation. When minerals are moistened hydrolysis occurs, producing only a chemical alteration but expansion in volume as well. This expansion can contribute to the breakdown of rocks. Hydrolysis, it should be noted, is not simply a matter of moistening: it is a true chemical alteration, and minerals are transformed into other mineral compounds in the process. For example, feldspar hydrolysis yields a clay mineral (silica)in solution(that is, dissolved in water), and a carbonate or bicarbonate of potassium, sodium. or calcium in solution. The new minerals tend to be softer and weaker than their predecessors. In granite boulders, hydrolysis combines with other process to cau the outer shells to flake off. 好好学习天天向上英语
awesome是什么意思When minerals in rocks react with oxygen in the air, the chemical process is known as oxidation. We have plenty of evidence of this process in the reddish color of soils in many
parts of the world and in the reddish brown hue of layers expod in such places as the Grand anyon. The products of oxidation are compounds of iron and aluminum, which account for the reddish colors en in so many rocks and soils. In tropical areas, oxidation is the dominant chemical-weathering process
Various circumstances may convert water into a mild acid solution, thereby increasing its effectiveness as a weathering agent. With a small amount of carbon dioxide. for instance. water forms carbonic acid, which in turn reacts with carbonate minerals such as limestone and dolomite(a harder relative of limestone). This form of chemical weathering, carbonation, is especially vigorous in humid areas, where limestone and dolomite formations are often deeply pitted and grooved, and where the evidence of solution and decay is prominent. This process even attacks limestone underground. contributing to the formation of caves and subterranean corridors. In arid areas, however, limestone and dolomite resist weathering much better, although they may show some evidence of carbonation at the surface
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iological weathering is the breakdown of rock caud by the actions of living organisms. This kind of weathering plays an important role in the formation of soils. It is through the breakdown of rocks and the accumulation of a layer of minerals that plants can grow--plants who roots and other parts, in turn, contribute to the weathering process. ut it is likely that the role of plant roots in weathering is somewhat overestimated. The roots follow paths of least resistance and adapt to every small irregularity in the rock. Roots certainly keep cracks open once they have been formed. More importantly, however, are as of roots tend to collect decaying organic material that is involved in chemical-weathering- process.
One of the most important aspects of biological weathering is the mixing of soil by burrowing animals and worms. nother interesting aspect is the action of lichens, a combination of algae and fungi that live on bare rock. Lichens draw minerals from the rock through an absorption process. The swelling and contraction of lichens as they alternately get wet and dry may also cau small particles of rock to fall off.
longmen1.The minerals that rocks are made of are subject to alteration by chemical weathering. Some minerals, such as here you are是什么意思quartz, resist this alteration quite successfully, but others, such as the calcium carbonate of aikulimestone, dissolve easily. In any rock made up of a combination of minerals, the chemical breakdown of one t of mineral grains leads to the disintegration of the whole mass. In granite(made chiefly of the minerals quartz and feldspar), the quartz resists chemical decay much more effectively than does the feldspar, which is chemically more reactive and weathers to become clay Often granite surfaces are heavily pitted (marked with many small holes or depressions). In such cas, the feldspar grains are likely to have been weathered to clay and blown or washed away. The quartz grains still remain, but they may eventually be looned too. So even rock as hard as granite cannot withstand the weathering process forever.
