Today magmatic rocks are the most common species, which make up about 65% of the total volume of the Earth's crust.These substances are formed from the liquid magma and are the result of its crystallization.
magmatic rocks and the mechanism of their formation
It's no secret that in the bowels of the earth is magma - a viscous substance that contains complex silicate complexes enriched gases and water vapors.The temperature of the molten magma places may be 1200 degrees Celsius.As a result of various geological processes (for example, the difference of tectonic plates, volcanic eruptions) molten magma moving to the surface.
As the temperature rise of magma substance falls - so there are processes of crystallization and the formation of new minerals.Primarily crystallized substances with high melting points - is amphibole and pyroxene.This happens as long as the entire mass of magma turns into resistant rock.
magmatic rocks and their structure
Rocks differ in their structure, which primarily depends on the speed with which solidified magma.If the substance cools slowly rising from the earth, it leads to the formation of large crystals.But the rapid cooling has the opposite effect - small crystals are formed.
But most often rise and cooling magma is mixed.Depending on the size of the crystals, igneous rocks separated into:
- ravnozernistuyu having the structure - they consist of crystals with respect to the same size (e.g., plutonic);
- with assorted structure - they contain crystals of different sizes.
Classification of magmatic rocks by the process of eruption and cooling magma:
1. Massive - are formed when magma erupts continuous stream.Among these species the following types:
- deep - magma cools at depth.These include diorite and granite;
- effusive - magma cools on the surface of the Earth (porphyry, basalt).
2. Vulkanooblomochnye breed - the name itself suggests, how the magma comes out of the bowels of the earth.Molten rock erupted in the form of sprays and splashes, cooling off in the air.It:
- loose rocks (volcanic sand and ash);
- cemented (eg, volcanic tuff).
magmatic rocks and mineralogical composition
Today there are four main types of minerals.Virtually any magmatic rocks is one of them.It:
- quartz - a mineral consisting of crystalline silica.This opaque crystals with a typical glass shine.The substance endures the impact of the external environment and can not be exposed to acids (except hydrofluoric).
- feldspars - a large group of minerals, which are characterized by lower (compared with quartz) hardness and perfect cleavage.They are painted in bright shades of different colors.Feldspars are divided into plagioclase and orthoclase.These minerals are easily weathered, turning to clay.
- Mica - a mineral with a perfect cleavage, and a low degree of hardness.The most common of this group - muscovite (transparent mica) and biotite (black).If the rock is made up of a large number of mica, its mechanical properties deteriorate significantly.
- pyroxene and amphibole - rock-forming minerals, which have a similar chemical composition.This generally silicates or magnesium double salts of calcium and magnesium.
Igneous rocks are significantly different from the sedimentary especially its chemical composition: they are composed of silicate or aluminosilicate.
