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Le rocce

rocks
To Rock means a natural aggregate of mineral crystalline or amorphous, and solid particles of various kinds, the rocks are not expressible substances with a chemical formula identifiable and generally well-formed masses.

rock types
Depending on the process that gives them the source rocks are divided into three broad categories:

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  The magmatic rocks are igneous rocks also known as generated by cooling of magma , a mass of molten silicate containing volatile elements: water, carbon dioxide, acids, hydrogen, etc ...) giving it fluidity and speed up chemical reactions. These rocks are in turn subdivided, depending on the speed and location of the cooling of magma, in plutonic or intrusive igneous rocks, extrusive or volcanic, or ipoabissali filoniane: the first formed in the earth's crust or in part highest mantle and are characterized by a slow cooling promotes the growth of crystals in them (about 150,000 years), typical of such rocks are granite and quartz-diorite, and the latter instead formed after an eruption or a lava flow and therefore undergo a rapid cooling (about a year) that "freezes" the rock in a state amorphous. They are composed of microcrystalline bottom paste, and their structure is glass. Examples are basalt the porphyry and pumice. Then there are the rocks or filoniane ipoabissali, which solidified below the earth's surface, but in small cavities, have a fast enough cooling. Igneous rocks constitute the large majority of the crust and mantle. Examples are the basalt, the granite the diorite.

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  The sedimentary rocks were generated for sedimentation of debris, inorganic, organic and mineral salts, consolidated the subsequent or simultaneous deposition of a cementing substance. This is, in essence, lithified ancient sediments as a result of stages of weathering, erosion, transportation and sedimentation. They are the most common rocks on Earth's surface because they cover more than 80% of the land. Examples are the ' sandstone, the limestone , the dolomite

• The metamorphic rocks are sedimentary or igneous rocks that have been made in terms of ( pressure and temperature ) different from those present for the lithification of the rock. Following these changes, the rock undergoes chemical and physical transformations that alter the mineralogical composition, for example. Examples include, alabaster and marble.

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