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| Magmas and lavas from volcanoes |
Rocks that brand up Earth'due south crust are circuitous aggregates of simpler particles, bonded to each other to form a well defined construction. Each rock is characterized by its chemical and mineralogical composition, as well equally the distribution and arrangement of its components (morphology). Commonly 2 or more than minerals amass, giving rise to rocks of unlike nature.
Unlike rocks accept different backdrop; this enables us to use them in different applications. Rocks are important sources of materials for sculpture and architecture.
Rocks may be classified, according to their origin, as: - Eruptive or Igneous obtained from the solidification of a molten mass
- Metamorphic formed following chemical transformation of pre-existing rocks
- Sedimentary produced by deposition and compounding of droppings from dissimilar sources
Igneous rocks
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| Igneous rocks are formed from solidification of magma and lava. When the process occurs slowly in the deep, then the rocks are chosen "intrusive". On the contrary if the solidification occurs on the surface at a college rate, "effusive" rocks grade. |
Igneous rocks ascend from solidification and crystallization of molten masses, magma and lava. Intrusive rocks, formed from slow cooling underneath the world'southward crust, are constituted past regular, often big crystals. Effusive rocks are produced on the surface of the earth post-obit a rapid cooling of lava and magma. They are constituted by pocket-size crystals and in some cases by glassy components, when time was not long enough to let the liquid crystallize.
Igneous rocks such as Granite, Porphyry and Basalt, due to their properties, have been used as materials for the manufacture of important artifacts of artistic and cultural value.
Metamorphic rocks
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| Scheme showing how a rock constituted of minerals A, B, C (left), through a metamorphic process due to the activeness of temperature and pressure, trasforms into another rock with a different mineralogical limerick (A,D,E,F). In this scheme mineral A does not alter. |
These rocks are formed by chemical and structural rearrangement of pre-existing rocks following the action of pressure and temperature.
The transformations, including both germination of new minerals and change of rock construction, occur in the solid state underneath the globe'south crust (up to 25 km deep) and are controlled by environmental factors, especially loftier temperatures (200-800 °C) and pressures (up to thousands of atmospheres).
A typical metamorphic procedure is transformation of quartz and calcareous rocks into rocks made of calcium silicates (Wollastonite) with emission of gaseous carbon dioxide. The reaction is:
SiOtwo (quartz) + CaCOthree (limestone) = CaSiO3 (wollastonite) + COtwo (carbon dioxide)
Marbles are stones of metamorphic origin that take been e'er used by human every bit materials for etching statues.
Sedimentary rocks
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| A system of natural sedimentary rocks with the typical layered structure. Zante, Greece |
They are formed following degradation and sedimentation of particles from various sources. These sediments may exist fragments or droppings of pre-existing rocks (mechanical sedimentation) or insoluble substances, the products of chemical reactions, precipitated at the lesser of sea or lake basins (sedimentation of precipitates). Quite ofttimes the droppings originate from remains (shells, skeletons, etc.) of water-living organisms such as mollusks, corals, etc. (biological sedimentation). In some circumstances sedimentary (pyroclastic) rocks course past deposition of lapilli, ash and dust ejected by volcanoes. Sedimentary rocks often give rise to typical layered structures.
Sandstones and Tuffs and several kinds of calcareous rocks, such every bit Travertine, Limestone, Dolomite, Alabaster, belong to the family of sedimentary rocks.
Transformations of rocks
Rocks, in the course of geologic eras, are subject to natural interconnected processes under the effects of concrete and chemical factors. They undergo transformations and exhibit phenomena of formation, alteration, disruption and formation of new rocks. - Magmas solidify and igneous rocks course.
- Igneous and sedimentary rocks are buried and subjected to heat, pressure, and the action of fluids. They change to metamorphic rocks.
- All kinds of rocks break down past weathering. Breakdown products are transported by erosion.
- Breakdown products are deposited, compacted and cemented, and form sedimentary rocks.
Metamorphic and sedimentary rocks may eventually exist heated enough to cook, forming a new generation of igneous rocks.
Source: http://www.whatischemistry.unina.it/en/rocce.html
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