The earth’s crust is the thin layer of rock which makes up to one percent of the whole planet and can range between 1 kilometer and 80 kilometer in different (Alden, 2010). The crust is made of two important types of rocks namely the basaltic (underlying the floor of the sea) and the granitic (the major components of the continent). The continental crust covers about 40% of the earth’s surface and is exposed to air. Of the nearly 4000 known minerals, only a few dozen constitute of the component of the earth’s crust.
These minerals make up the rocks of the crust and therefore are referred to as the rock-forming minerals. Of these, the eight most important elements are Oxygen, Silicon, Aluminum, Iron, Calcium, Sodium, Potassium, and Magnesium. They constitute of the highest percentage of these minerals and represent more than 98% of the earth’s continental crust by weight. Of these eight minerals, it is rational to assert the fact that Oxygen and silicon are the most important of all. This is because each of the silicates minerals, being the most common mineral group contains silicon and oxygen.
In addition, these two elements make up the largest percentage of mineral constituent of the earth’s crust with silicon accounting for 27. 7% and oxygen 46. 6%. Some of the important physical characteristic or properties used to identify minerals include crystal shape, color, luster, streak, hardness, fracture, cleavage, and density or special gravity among others. Habit refers to the characteristic crystal shape of the elements making up a rock. The shape is mostly unique and is used for identification of specific minerals.
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Mineral strength or simply hardness refers to the degree at which minerals withstand stress before breaking and is determined by the type of bond forming between the atoms of the element. When identifying minerals, it would be inconvenient to use habit as a mean of identification. This is because some minerals such as pyrite have been shown to demonstrate more than one crystal shapes hence not a very reliable method of identification. The least useful method of identification includes taste and magnetism. This is because they are less distinct for a particular mineral and therefore other well developed properties can be used.
Question 2 Weathering is the gradual change of material on the earth’s surface in response to the changing climatic conditions. It is classified in to two: physical and chemical weathering. Physical weathering occurs when these materials break into smaller particles due to biological activities, frost wedging and expansion due to unloading. Chemical weathering occurs when chemical reactions take place leading to removal or addition of minerals. Among various environmental factors that specifically affect both physical and chemical weathering includes amount of rainfall, temperature, and rain acidity.
Chemical processes are more rapid and pervasive in moist and warm conditions. Increased temperature leads to expansion of rocks; when the temperature drops instantly, it leads to fragmentation of rocks. On the other hand, increased temperature can lead to increased rate of chemical reactions that enhance the process of chemical weathering. The acidity of rainfall is determined by the amount of dissolved gases in rain water. The main gases that results in acidic rain includes carbon dioxide and sulphur dioxide. Acidic rainfall leads to corrosion of rocks hence increasing the rate of physical weathering.
The higher the amount of acid is the higher the rate of weathering. The most important factor is the amount of rainfall. Water is basically the basis for almost every other factor to cause their effect. To start with, Chemical reactions occur in water which means that the higher the amount of water in a rock the higher the process of weathering. Secondly, when water freezes inside rocks it causes physical weathering. In addition, it enhances the process of frost wedging. References Alden, A. (2010). The earth’s crust. Retrieved August 19, 2010, form http://geology. about. com/od/platetectonics/a/thecrust. htm
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