Igneous Essay Example | Topics and Well Written Essays - 1000 words

Igneous - Essay Example Igneous rocks are made when molten rock material called magma cools and solidifies. Magma may be thought of as a molten rock but it is not regularly a simple molten fluid. Nonetheless, it is rather a multifaceted blend of molten solid materials, for example, crystals, rocks, as well as dissolved vapor. Magma’s chemical composition and physical properties such as viscosity and density are all important factors that control magma’s overall behavior, for instance, how fast or slow it will move, how explosive it will be, what minerals will form in it, and their grain sizes and physical interrelationships. In terms of chemical composition, all magmas except rare carbonites are rich in carbonate component. They are also silicate magmas in which the dominant component is silica (SiO2), which generally comprises 45 % or more by weight. Alumina (Al2O3), with its abundance in common igneous rocks anywhere between 13 and 18 %, is at a distant second. Igneous rocks are categorized according to location, chemical composition, surface consistency, and mineralogy. Two significant factors used for the taxonomy of igneous rocks are the rock grain size, which largely depends on the cooling history, determines the texture and the mineral or chemical composition of the rock (Krebs, 2003 p. 95). The identification of these rocks is majorly done by texture. The grain consistency of volcanic rocks comprising the size, distribution of mineral grains, shape, orientation, and the intergranular relationships will decide if the rock is designated as simple or pyroclastic lava, or a tuff. Subsequently, it also determines what minerals are found in what kind of igneous rock. These are large rocks with mineral grains that are big enough to be identified by the eye. They are formed when magma slowly cools to form intrusive mafic igneous rocks. The well