Magmatic rocks

Today, igneous rocks are considered to be the most common rocks, which account for approximately 65% of the total volume of the earth's crust. These substances are formed from liquid magma and are the result of its crystallization.

Magmatic rocks and the mechanism of their formation

It's not a secret that in the bowels of the earth is a magma - a viscous substance that contains complex silicate complexes, enriched with gases and water vapor. The temperature of the molten magma in places can be 1200 degrees Celsius. As a result of various geological processes (for example, the divergence of tectonic plates, volcanic eruptions), the molten magma moves to the earth's surface.

As the temperature of the magmatic substance rises, the crystallization process and the formation of new minerals take place. First of all, substances with a high melting point crystallize-these are amphiboles and pyroxenes. This happens until the entire mass of magma is transformed into a resistant rock.

Magmatic rocks and their structure

The rocks differ in their structure, which primarily depends on the speed with which the magma solidifies. If the substance cools slowly, rising from the earth's interior, this leads to the formation of large crystals. But rapid cooling gives the opposite effect - small crystals are formed.

But most often the rise and cooling of magma is mixed. Depending on the size of the crystals, igneous rocks are divided into:

• Having an even grain structure - they consist of crystals of relatively the same size (for example, plutonic);
• Having a heterogeneous structure - they consist of crystals of different sizes.

Classification of igneous rocks by the method of eruption and cooling of magma:

1. Massive - are formed in the event that magma erupts in a continuous stream. Among such breeds the following types are distinguished:

• Deep - magma cools down at depth. Here you can include diorite and granite;
• Discharged - magma cools on the surface of the Earth (porphyrite, basalt).

2. Volcanic clastic rocks - the name itself indicates how exactly magma emerges from the earth's interior. Molten rocks erupt in the form of splashes and splashes, cooling in the air. It:

• Loose rocks (volcanic sand and ash);
• Cemented (for example, volcanic tuff).

Magmatic rocks and their mineralogical composition

To date, there are four main types of minerals. Virtually every magmatic rock consists of them. It:

• Quartz is a mineral consisting of crystalline silica. These are opaque crystals with a characteristic glass luster. The substance is resistant to the influence of the environment and is not affected by acids (except hydrofluoric).
• Feldspar - a large group of minerals, which are characterized by a lower (in comparison with quartz) hardness and perfect cleavage. They are painted in light shades of different colors. Field feldspars are usually divided into plagioclases and orthoclases. These minerals are easily weathered, turning into clay.
• Mica is a mineral with perfect cleavage and a low degree of hardness. The most common representatives of this group are muscovite (transparent mica) and biotite (black). If the rock consists of a large amount of mica, its mechanical properties deteriorate considerably.
• Pyroxenes and amphiboles are rock-forming minerals that have a similar chemical composition. As a rule, these are magnesium silicates or double salts of calcium and magnesium.

Magmatic rocks differ significantly from sedimentary rocks primarily by their chemical composition: they consist of silicates or aluminosilicates.